In-situ formed (Cu0.6Zr0.3Ti0.1)95Nb5 bulk metallic glass (BMG) composite with Nb-rich dendrite randomly dispersed in hard glassy matrix was prepared by casting into a water-cooled copper mold. The dendrite has mu...In-situ formed (Cu0.6Zr0.3Ti0.1)95Nb5 bulk metallic glass (BMG) composite with Nb-rich dendrite randomly dispersed in hard glassy matrix was prepared by casting into a water-cooled copper mold. The dendrite has much smaller hardness and elastic modulus than glassy matrix, and the stress concentration at interface provides a channel for the initiating and branching of shear bands upon loading, thus leading to a high compressive fracture strain of 6.08% and fracture strength about 2200 MPa. Comparing with other Cu-based BMG composite, the fracture strength of present (Cu0.6Zr0.3Ti0.1)95Nb5 composite is not significantly reduced, indicating that the addition of Nb in the current work is an effective and effortless way to fabricate new practical BMG composites with enhanced strength and good plasticity.展开更多
The unusual glass-forming ability(GFA) of the Zr48Cu36Ag8Al8 alloy and the high ductility of the Zr48Cu36Ag8Al8 metallic glass-matrix composites containing Ta powder were reported.The bulk metallic glass rod with a ...The unusual glass-forming ability(GFA) of the Zr48Cu36Ag8Al8 alloy and the high ductility of the Zr48Cu36Ag8Al8 metallic glass-matrix composites containing Ta powder were reported.The bulk metallic glass rod with a diameter of 25 mm was successfully synthesized using copper mold casting for the Zr48Cu36Ag8Al8 alloy.High GFA of this alloy was found to be related to a large supercooled liquid region and a quaternary eutectic point with low melting temperature.The bulk metallic glass matrix composites were prepared by introducing extra Ta particles into the Zr48Cu36Ag8Al8 melt.The composites consist of Ta particles homogenously distributed in the Zr48Cu36Ag8Al8 metallic glass matrix.The optimum content of Ta powder is 10at%for the composite with the highest plasticity,which shows a plastic strain of 31%.展开更多
Cu47Ti34Zr11Ni8 bulk metallic glass (BMG) matrix composites containing in situ formed TiC particles and 5-TiCu dendrite phase were developed by copper mold cast. The thermal stability and microstructure of the compo...Cu47Ti34Zr11Ni8 bulk metallic glass (BMG) matrix composites containing in situ formed TiC particles and 5-TiCu dendrite phase were developed by copper mold cast. The thermal stability and microstructure of the composites are investigated. Room temperature compression tests reveal that the composite samples exhibit higher fracture strength and distinct plastic strain of 0.2%-0.5%, comparing with that of the corresponding Cu47Ti34Zr11Ni8 monolithic BMG.展开更多
The coupling effects of the metastable austenitic phase and the amorphous matrix in a transformation-induced plasticity(TRIP)-reinforced bulk metallic glass(BMG)composite under compressive loading were investigated by...The coupling effects of the metastable austenitic phase and the amorphous matrix in a transformation-induced plasticity(TRIP)-reinforced bulk metallic glass(BMG)composite under compressive loading were investigated by employing the digital image correlation(DIC)technique.The evolution of local strain field in the crystalline phase and the amorphous matrix was directly monitored,and the contribution from the phase transformation of the metastable austenitic phase was revealed.Local shear strain was found to be effectively consumed by the displacive phase transformation of the metastable austenitic phase,which relaxed the local strain/stress concentration at the interface and thus greatly enhanced the plasticity of the TRIP-reinforced BMG composites.Our current study sheds light on in-depth understanding of the underlying deformation mechanism and the interplay between the amorphous matrix and the metastable crystalline phase during deformation,which is helpful for design of advanced BMG composites with further improved properties.展开更多
A series of rod samples with diameter of 3 mm(Zr0.55Al0.10Ni0.05Cu0.30)100-xFex(x=0,1,2,3,4) were prepared by magnetic suspend melting and copper mold suction casting method.The effects of a small amount of Fe on ...A series of rod samples with diameter of 3 mm(Zr0.55Al0.10Ni0.05Cu0.30)100-xFex(x=0,1,2,3,4) were prepared by magnetic suspend melting and copper mold suction casting method.The effects of a small amount of Fe on glass forming ability(GFA) and mechanical properties of Zr55Al10Ni5Cu30 bulk metallic glass(BMG) were investigated.The results show that the addition of an appropriate amount(less than 3%,mole fraction) of Fe enhances GFA,as indicated by the increase in the reduced glass transition temperature Trg(=Tg/Tl) and the parameter γ(=Tx/(Tg+Tl)) with increasing Fe content,and GFA gets deteriorated by further Fe addition(4%).The addition of Fe also effectively improves the compressive plasticity and increases the compressive fracture strength in these Zr-based BMGs.Compressive tests on BMG sample with 3 mm in diameter and 6 mm in length reveal work-hardening and a certain plastic strain in the alloy containing 2% Fe.The BMG composite containing 4% Fe also exhibits a high fracture strength along with significant plasticity.展开更多
A dendritic β-phase reinforced bulk metallic glass(BMG) composite named as D2 was prepared by rapid quenching of a homogenous Zr60Ti14.67Nb5.33Cu5.56Ni4.44Be10 melt, and characterized by means of X-ray diffraction(XR...A dendritic β-phase reinforced bulk metallic glass(BMG) composite named as D2 was prepared by rapid quenching of a homogenous Zr60Ti14.67Nb5.33Cu5.56Ni4.44Be10 melt, and characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM) observation and room-temperature compression test. The microstructure and mechanical properties were compared with those of the spherical β-phase reinforced composite named as composite S2. It was found that the composite D2 contains β-phase dendrites up to 56% in volume-fraction, and exhibits a ductile compressive behavior with plastic strain of 12.7%. As the high-volumefractioned β-phase dendrites transferred to coarse spherical particles of about 20 μm in diameter in the composite S2, a much improved plastic strain up to 20.4% can be achieved. Micrographs of the fractured samples reveal different interaction modes of the propagating shear bands with the dendritic and spherical β phase inclusions, resulting in different shear strains in the composite samples. The matrix of composite S2 undergoes a significantly larger shear strain than that of the composite D2 before ultimate failure, which is thought to be mainly responsible for the greatly increased global plastic strain of the S2 relative to D2.展开更多
(Cu_(43)Zr_(48)Al_(9))_(98)Y_(2)-based bulk metallic glass composites(BMGCs)with dispersed Ta particles(3vol.%,6vol.%,9vol.%)were successfully fabricated through suction casting.The thermal properties,microstructure,a...(Cu_(43)Zr_(48)Al_(9))_(98)Y_(2)-based bulk metallic glass composites(BMGCs)with dispersed Ta particles(3vol.%,6vol.%,9vol.%)were successfully fabricated through suction casting.The thermal properties,microstructure,and mechanical properties of the BMGCs were systematically investigated.Ta particles are homogeneously dispersed in the amorphous matrix.Ta particle reinforced BMGCs exhibit similar thermal properties and glass-forming ability with the Cu_(43)Zr_(48)Al_(9))_(98)Y_(2)base BMG.Compression test results show that the BMGC with 9vol.%Ta particles has superior mechanical performance with up to 15.7%compressive plastic strain,2,216 MPa yield strength,and 2,260 MPa fracture strength at room temperature.These homogeneously distributed Ta particles act as discrete obstacles in the amorphous matrix,restricting the highly localized shear band.This results in the formation of multiple shear bands around the Ta-rich particles,which lowers the stress concentration,allowing the shear band to propagate further and improve plasticity.展开更多
Bulk metallic glass and their composites (BMGMCs) are a new class of materials which possess superior mechanical properties as compared to existing conventional materials. Owing to this, they are potential candidates ...Bulk metallic glass and their composites (BMGMCs) are a new class of materials which possess superior mechanical properties as compared to existing conventional materials. Owing to this, they are potential candidates for tomorrow’s structural applications. However, they suffer from poor ductility and little or no toughness which render them brittle and they manifest catastrophic failure under applied force. Their behavior is dubious, unpredictable and requires extensive experimentation to arrive at conclusive results. In present study, an effort has been made to design bulk metallic glass matrix composites by the use of modeling and simulation. A probabilistic cellular automaton (CA) model is developed and described in present study by author which is used in conjunction with earlier developed deterministic model to predict microstructural evolution in Zr based BMGMCs in additive manufacturing liquid melt pool. It is elaborately described with an aim to arrive at quantitative relations which describe process and steps of operations. Results indicate that effect of incorporating all mass transfer and diffusion coefficients under transient conditions and precise determination of probability number play a vital role in refining the model and bringing it closer to a level that it could be compared to actual values. It is shown that proposed tailoring can account for microstructural evolution in metallic glasses.展开更多
The glass-forming ability and mechanical properties of metallic glasses and their composites are well known to be sensitive to the preparation conditions and are highly deteriorated by industrial preparing conditions ...The glass-forming ability and mechanical properties of metallic glasses and their composites are well known to be sensitive to the preparation conditions and are highly deteriorated by industrial preparing conditions such as low-purity raw materials and low vacuum.Here,we showed that a series of in-situ bulk metallic glass composites(BMGCs)which exhibit excellent ductility and segmental work hardening were successfully developed utilizing a high vacuum high-pressure die casting(HV-HPDC)technology along with industrial-grade raw materials.The tensile properties of these BMGCs are systematically investigated and correlated with the alloy microstructure.As compared with the copper mold suction casting method,the volume fraction difference of the dendrite phase for the BMGCs with the same composition is not significant when fabricated by the HV-HPDC,whereas the size of theβ-phase is generally larger.Insitu BMGCs with the composition of Ti_(48)Zr_(20)(V_(12/17)Cu_(5/17))19 Be 13 obtained by the HV-HPDC process show ductility up to 11.3%under tension at room temperature and exhibit a certain amount of work hardening.Two conditions need to be met to enable the BMGCs,which are prepared by vacuum die-casting to retain favorable ductility:(1)The volume fraction ofβphase stays below 62%±2%;(2)The equiaxed crystals with a more uniform size in the range of 5-10μm.Meanwhile,the results of the present study provided guidance for developing BMGCs with good ductile properties under industrial conditions.展开更多
Additive manufacturing technology based on laser powder bed fusion(LPBF)offers a novel approach for fabricating bulk metallic glass(BMG)products without restriction in size and geometry.Nevertheless,the BMGs prepared ...Additive manufacturing technology based on laser powder bed fusion(LPBF)offers a novel approach for fabricating bulk metallic glass(BMG)products without restriction in size and geometry.Nevertheless,the BMGs prepared by LPBF usually suffered from less plasticity and poorer fracture toughness as compared to their cast counterparts due to partial crystallization in heat-affected zones(HAZs).Since crystallization in HAZs is hard to avoid completely in LPBF BMGs,it is desirable to design a suitable alloy system,in which only ductile crystalline phase,instead of brittle intermetallics,is formed in HAZs.This unique structure could effectively increase the toughness/plasticity of the LPBF BMGs.To achieve this goal,a quaternary BMG system with a composition of Zr_(47.5)Cu_(45.5)Al_(5)Co_(2)is adopted and subjected to LPBF.It is found that nearly a single phase of B_(2)-ZrCu is precipitated in HAZs,while a fully amorphous phase is formed in molten pools(MPs).This B_(2)phase reinforced BMG composite exhibits excellent mechanical properties with enhanced plasticity and toughness.Furthermore,it is easy to modulate the mechanical properties by altering the amount of the B_(2)phase via adjusting the laser energy input.Finally,the best combination of strength,plasticity,and notch toughness is obtained in the BMG composite containing 27.4%B_(2)phase and 72.6%amorphous phase,which exhibits yield strength(σ_(s))of 1423 MPa,plastic strain(ε_(p))of 4.65%,and notch toughness(K_(q))of 53.9 MPa m 1/2.Furthermore,a notable strain-hardening is also observed.The improvement of plasticity/toughness and appearance of strain-hardening behavior are mainly due to the martensite phase transformation from the B_(2)phase to the Cm phase during plastic deformation(i.e.,the phase transformation-induced plasticity effect).The current work provides a guide for making advanced BMGs and BMG composites by additive manufacturing.展开更多
Starting with Zr of two different purities, Ti-based bulk metallic glasses (BMGs) with a nominal composition of Ti40Zr25Cu12Ni3Be20 were prepared. The effect of the addition of yttrium at levels of 0.2 at.%, 0.4 at....Starting with Zr of two different purities, Ti-based bulk metallic glasses (BMGs) with a nominal composition of Ti40Zr25Cu12Ni3Be20 were prepared. The effect of the addition of yttrium at levels of 0.2 at.%, 0.4 at.%, 0.5 at.%, 0.6 at.%, and 1 at.% on the glass forming ability (GFA) of the alloy has been investigated by means of metallography, X-ray diffraction, and differential scanning calorimetry. Experimental data in-dicates that high impurity content dramatically reduces the glass forming ability. Microalloying with 0.5 at.% Y is effective in suppressing the crystalline phase formation and alleviating the detrimental effect of oxygen in the low-purity alloy. On the contrary, in the alloy contain-ing high-purity element, the effective yttrium addition is less than 0.4 at.%. The results indicate that the beneficial effect of the optimum dopants is mainly due to scavenging the oxygen impurity via the formation of innocuous phase.展开更多
The formation of bulk metallic glasses(BMGs) in the ternary Zr(56) Co(28-x)Al(16) and quaternary Zr(56) Co(28-x)CuxAl16(x=2, 4, 5, 6, 7, mole fraction, %) glassy alloys was investigated via the copper mo...The formation of bulk metallic glasses(BMGs) in the ternary Zr(56) Co(28-x)Al(16) and quaternary Zr(56) Co(28-x)CuxAl16(x=2, 4, 5, 6, 7, mole fraction, %) glassy alloys was investigated via the copper mold suction casting method. The main purpose of this work was to locate the optimal BMG-forming composition for the quaternary Zr Co(Cu)Al alloys and to improve the plasticity of the parent alloy. The X-ray diffractometry(XRD), transmission electron microscopy(TEM) and differential scanning calorimetry(DSC) were used to investigate the glassy alloys structure and their glass forming ability(GFA). In addition, the compression test, microhardness, nano-indentation and scanning electron microscopy(SEM) were utilized to discuss the possible mechanisms involved in the enhanced plasticity achievement. The highest GFA among Cu-containing alloys was found for the Zr(56) Co(22) Cu6 Al(16) alloy, which was similar to that of the base alloy. Furthermore, the plasticity of the base alloy increased significantly from 3.3% to 6% for the Zr(56) Co(22) Cu)6 Al(16) BMG. The variations in the plasticity and GFA of the alloys were discussed by considering the positive heat of mixing within Cu and Co elements.展开更多
Cu47Ti33Zr11Ni6Sn2Si1-based bulk metallic glass matrix composites reinforced with tungsten wires were fabricated by infiltration process at different temperatures (850, 900, 950 and 1000 °C) and time (10, 20 a...Cu47Ti33Zr11Ni6Sn2Si1-based bulk metallic glass matrix composites reinforced with tungsten wires were fabricated by infiltration process at different temperatures (850, 900, 950 and 1000 °C) and time (10, 20 and 30 min) in a quartz or a steel tube. The mechanical tests were carried out by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the maximum strength and total strain of the composite are 1778 MPa and 2.8% fabricated in steel tube at 900 °C for 10 min, and 1582 MPa and 3.6% fabricated in quartz tube at 850 °C for 10 min, respectively.展开更多
According to the Gibbs free energy difference between liquid and crystal,a thermodynamic glass-forming ability(GFA) parameter related to characteristic temperatures,onset crystallization temperature(Tx)and liquidus te...According to the Gibbs free energy difference between liquid and crystal,a thermodynamic glass-forming ability(GFA) parameter related to characteristic temperatures,onset crystallization temperature(Tx)and liquidus temperature(Tl),was proposed for evaluating the GFA of bulk metallic glasses(BMGs).The new parameter defined asω=Tl(Tl+Tx)/(Tx(Tl-Tx))has good correlation with the critical section thickness(Zc)of Ca-Mg-Cu BMGs.Being verified by the glasses data,including oxide glasses,which were used to validate the former GFA parameters,ωis one of the most reliable and applicable GFA parameters among Trg(=Tg/Tl), γ(=Tx/(Tl+Tg)),α(=Tx/Tl),δ(=Tx/(Tl-Tg),and so on.Finally,predicting GFA of Cu-Ag-Zr-Ti and Cu-Zr-Ti-Al BMGs usingωwas compared with the experimental results.展开更多
The effect of the cooling slope on the structure of Zr-based metallic glass matrix composites was investigated by changing the cooling slope.The synthesis of bulk metallic glass composites was made by a process combin...The effect of the cooling slope on the structure of Zr-based metallic glass matrix composites was investigated by changing the cooling slope.The synthesis of bulk metallic glass composites was made by a process combining cooling slope casting and Cu mold casting for Zr66.4Nb6.4Cu10.5Ni8.7Al8 alloys.The results show that the semisolid slurry which consists of the spheroidal or rosette-type BCC crystals and the liquid phase which forms metallic glass phase can be formed by the cooling slope process in this alloy system.However,the semisolid slurry cannot reach to the mold.It is considered that higher viscosity of the liquid phase which forms metallic glass phase causes this result.Thus,parameters of the cooling slope have to be examined further.展开更多
Bulk metallic glass (BMG) formation was explored in the Fe-B-Si-Nb alloy system though combined use of the atomic cluster line approach and the minor alloying strategy. The basic ternary compositions in the Fe-B-Si ...Bulk metallic glass (BMG) formation was explored in the Fe-B-Si-Nb alloy system though combined use of the atomic cluster line approach and the minor alloying strategy. The basic ternary compositions in the Fe-B-Si system were determined by the intersection points of two cluster lines, namely, Fe-B cluster to Si and Fe-Si cluster to B. 3at% -4at% Nb was added to the quaternary Fe-B-Si-Nb alloy. The casting experiments revealed that good glass-forming ability (GFA) occurred at the (Fe73.4Si8.2B18.4)96Nb4 composition, and 3-mm diameter BMG samples were made. The glass transition temperature (Tg), crystallization temperature (Tx), and supercooled liquid region (△Tx=Tx-Tg) of this BMG were measured to be 866, 889, and 23 K, respectively. The BMG shows a high Vickers hardness of about Hv 1164, a Young's modulus of 180 GPa, and a good corrosion resistance in the solutions of 1 mol/L HCl and 3wt% NaCl.展开更多
Bulk amorphous Cu52.5Ti30Zr11.5Ni6 and Cu53.1Ti31.4Zr9.5Ni6 alloys with a high glass forming ability can be quenched into single amorphous rods with a diameter of 5 mm, and exhibit a high fracture strength of 2 212 MP...Bulk amorphous Cu52.5Ti30Zr11.5Ni6 and Cu53.1Ti31.4Zr9.5Ni6 alloys with a high glass forming ability can be quenched into single amorphous rods with a diameter of 5 mm, and exhibit a high fracture strength of 2 212 MPa and 2 184 MPa under compressive condition, respectively. The stress—strain curves show nearly 2% elastic strain limit, yet display no appreciable macroscopic plastic deformation prior to the catastrophic fracture due to highly localized shear bands. The present work shows clearly evidence of molten droplets besides well-developed vein patterns typical of bulk metallic glasses on the fracture surface, suggesting that localized melting induced by adiabatic heating may occur during the final failure event.展开更多
The bulk Fe<sup>60 CoxZr<sup>10 Mo5W2B<sup>23-x (x=1, 3, 5, 7, 9) amorphous rods with diameters of 1.5 mm were successfully prepared by copper mold casting method with the low purity raw materials....The bulk Fe<sup>60 CoxZr<sup>10 Mo5W2B<sup>23-x (x=1, 3, 5, 7, 9) amorphous rods with diameters of 1.5 mm were successfully prepared by copper mold casting method with the low purity raw materials. The amorphous and crystalline states, and thermal parameters, such as the glass transition temperature (Tg), the initial crystallization temperature (Tx), the supercooled liquid region (ΔTx=Tx-Tg), the reduced glass transition temperature T<sup>rg (Tg/Tm, Tm: the onset temperature of melting of the alloy, and Tg/Tl, Tl: the finished temperature of melting of the alloy) were investigated by X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) analysis. Glass forming ability of Fe<sup>60 CoxZr<sup>10 Mo5W2B<sup>23-x (x=1,3,5,7,9) bulk metallic glasses has been studied. According to the results, the alloy (x=7) with the highest T<sup>rg (Tg/Tl=0.607, Tg/Tl=0.590) value, has the strongest glass forming ability among these alloys because its composition is near eutectic composition. The wide supercooled liquid region over 72 K indicates the high thermal stability for this alloy system. This bulk metallic glass exhibits quite high strength (Hv 1020). The success of production of the Fe-based bulk metallic glass with industrial materials is of great significance for the future progress of basic research and practical application.展开更多
The formation and thermal stabilities of Cu46.25Zr46.25xAl7.5Erx (x=0 to 8) bulk metallic glasses (BMGs) were investigated. The addition of a small amount of Er (2at%) for replacing Zr effectively improves the glass-f...The formation and thermal stabilities of Cu46.25Zr46.25xAl7.5Erx (x=0 to 8) bulk metallic glasses (BMGs) were investigated. The addition of a small amount of Er (2at%) for replacing Zr effectively improves the glass-forming ability of Cu46.25Zr46.25Al7.5 alloy, and the glassy rod with a diameter of at least 12 mm can be formed. The glass transition temperature (Tg), temperature interval of su- percooled liquid region △Tx (=Tx-Tg), and reduced glass transition temperature Trg (=Tg/Tl) of Cu46.25Zr44.25Al7.5Er2 glassy alloy are 699 K, 62 K and 0.607, respectively.展开更多
The effect of partial substitution of Al for Cu on the glass forming ability(GFA) and mechanical properties of Mg65Cu25-xAlxGd10 (x=0, 1, 3 and 5, molar fraction, %) alloys were studied by X-ray diffractometry(XRD), d...The effect of partial substitution of Al for Cu on the glass forming ability(GFA) and mechanical properties of Mg65Cu25-xAlxGd10 (x=0, 1, 3 and 5, molar fraction, %) alloys were studied by X-ray diffractometry(XRD), differential scanning calorimetry(DSC) and uniaxial compression test. The result reveals that GFA of the alloys changes slightly with increasing x from 0 to 3, and then abruptly decreases with x increasing up to 5. The plasticity can be greatly improved with appropriate substitution of Cu by Al (3%, molar fraction) in Mg65Cu25Gd10 bulk metallic glass, and the resultant fracture strength, total strain to failure, and plastic strain are 898 MPa, 2.19% and 0.2%, respectively.展开更多
基金Project(51371149)supported by the National Natural Science Foundation of ChinaProject(151048)supported by the HUO Ying-dong Young Teacher Fund+4 种基金Project(2015ZF53066)supported by the Aeronautical Science Foundation of ChinaProject(92-QZ-2014)supported by the Free Research Fund of State Key Laboratory of Solidification Processing,ChinaProject(2015KJXX-10)supported by Shaanxi Young Stars of Science and Technology,ChinaProejct(2011CB610403)supported by the National Basic Research Program of ChinaProject(51125002)supported by the National Science Funds for Distinguished Young Scientists,China
文摘In-situ formed (Cu0.6Zr0.3Ti0.1)95Nb5 bulk metallic glass (BMG) composite with Nb-rich dendrite randomly dispersed in hard glassy matrix was prepared by casting into a water-cooled copper mold. The dendrite has much smaller hardness and elastic modulus than glassy matrix, and the stress concentration at interface provides a channel for the initiating and branching of shear bands upon loading, thus leading to a high compressive fracture strain of 6.08% and fracture strength about 2200 MPa. Comparing with other Cu-based BMG composite, the fracture strength of present (Cu0.6Zr0.3Ti0.1)95Nb5 composite is not significantly reduced, indicating that the addition of Nb in the current work is an effective and effortless way to fabricate new practical BMG composites with enhanced strength and good plasticity.
基金supported by Grant-In-Aid for Scientific Research(C)(No.19560689)
文摘The unusual glass-forming ability(GFA) of the Zr48Cu36Ag8Al8 alloy and the high ductility of the Zr48Cu36Ag8Al8 metallic glass-matrix composites containing Ta powder were reported.The bulk metallic glass rod with a diameter of 25 mm was successfully synthesized using copper mold casting for the Zr48Cu36Ag8Al8 alloy.High GFA of this alloy was found to be related to a large supercooled liquid region and a quaternary eutectic point with low melting temperature.The bulk metallic glass matrix composites were prepared by introducing extra Ta particles into the Zr48Cu36Ag8Al8 melt.The composites consist of Ta particles homogenously distributed in the Zr48Cu36Ag8Al8 metallic glass matrix.The optimum content of Ta powder is 10at%for the composite with the highest plasticity,which shows a plastic strain of 31%.
基金The authors acknowledge the financial support provided by the Knowledge Innovation Program of Chinese Academy of Sciences,No.KJCX2-SW-L05the National Natural Science Foundation of China,No.50101012.
文摘Cu47Ti34Zr11Ni8 bulk metallic glass (BMG) matrix composites containing in situ formed TiC particles and 5-TiCu dendrite phase were developed by copper mold cast. The thermal stability and microstructure of the composites are investigated. Room temperature compression tests reveal that the composite samples exhibit higher fracture strength and distinct plastic strain of 0.2%-0.5%, comparing with that of the corresponding Cu47Ti34Zr11Ni8 monolithic BMG.
基金financially supported by the National Natural Science Foundation of China(Nos.52061135207,51871016,51921001,11790293,and 51971017)111 Project(No.B07003)the Projects of SKL-AMM-USTB(Nos.2019Z-01 and 2018Z-19)。
文摘The coupling effects of the metastable austenitic phase and the amorphous matrix in a transformation-induced plasticity(TRIP)-reinforced bulk metallic glass(BMG)composite under compressive loading were investigated by employing the digital image correlation(DIC)technique.The evolution of local strain field in the crystalline phase and the amorphous matrix was directly monitored,and the contribution from the phase transformation of the metastable austenitic phase was revealed.Local shear strain was found to be effectively consumed by the displacive phase transformation of the metastable austenitic phase,which relaxed the local strain/stress concentration at the interface and thus greatly enhanced the plasticity of the TRIP-reinforced BMG composites.Our current study sheds light on in-depth understanding of the underlying deformation mechanism and the interplay between the amorphous matrix and the metastable crystalline phase during deformation,which is helpful for design of advanced BMG composites with further improved properties.
基金Project(50371016) supported by the National Natural Science Foundation of ChinaProject(50611130629) supported by the International Cooperation and Exchange of the National Natural Science Foundation of China
文摘A series of rod samples with diameter of 3 mm(Zr0.55Al0.10Ni0.05Cu0.30)100-xFex(x=0,1,2,3,4) were prepared by magnetic suspend melting and copper mold suction casting method.The effects of a small amount of Fe on glass forming ability(GFA) and mechanical properties of Zr55Al10Ni5Cu30 bulk metallic glass(BMG) were investigated.The results show that the addition of an appropriate amount(less than 3%,mole fraction) of Fe enhances GFA,as indicated by the increase in the reduced glass transition temperature Trg(=Tg/Tl) and the parameter γ(=Tx/(Tg+Tl)) with increasing Fe content,and GFA gets deteriorated by further Fe addition(4%).The addition of Fe also effectively improves the compressive plasticity and increases the compressive fracture strength in these Zr-based BMGs.Compressive tests on BMG sample with 3 mm in diameter and 6 mm in length reveal work-hardening and a certain plastic strain in the alloy containing 2% Fe.The BMG composite containing 4% Fe also exhibits a high fracture strength along with significant plasticity.
基金supported by the State Key Lab.of Advanced Metals and Materials,China(Grant No.2012-Z07)
文摘A dendritic β-phase reinforced bulk metallic glass(BMG) composite named as D2 was prepared by rapid quenching of a homogenous Zr60Ti14.67Nb5.33Cu5.56Ni4.44Be10 melt, and characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM) observation and room-temperature compression test. The microstructure and mechanical properties were compared with those of the spherical β-phase reinforced composite named as composite S2. It was found that the composite D2 contains β-phase dendrites up to 56% in volume-fraction, and exhibits a ductile compressive behavior with plastic strain of 12.7%. As the high-volumefractioned β-phase dendrites transferred to coarse spherical particles of about 20 μm in diameter in the composite S2, a much improved plastic strain up to 20.4% can be achieved. Micrographs of the fractured samples reveal different interaction modes of the propagating shear bands with the dendritic and spherical β phase inclusions, resulting in different shear strains in the composite samples. The matrix of composite S2 undergoes a significantly larger shear strain than that of the composite D2 before ultimate failure, which is thought to be mainly responsible for the greatly increased global plastic strain of the S2 relative to D2.
基金the President Fund of Xi'an Technological University(Grant No.0852-302021407).
文摘(Cu_(43)Zr_(48)Al_(9))_(98)Y_(2)-based bulk metallic glass composites(BMGCs)with dispersed Ta particles(3vol.%,6vol.%,9vol.%)were successfully fabricated through suction casting.The thermal properties,microstructure,and mechanical properties of the BMGCs were systematically investigated.Ta particles are homogeneously dispersed in the amorphous matrix.Ta particle reinforced BMGCs exhibit similar thermal properties and glass-forming ability with the Cu_(43)Zr_(48)Al_(9))_(98)Y_(2)base BMG.Compression test results show that the BMGC with 9vol.%Ta particles has superior mechanical performance with up to 15.7%compressive plastic strain,2,216 MPa yield strength,and 2,260 MPa fracture strength at room temperature.These homogeneously distributed Ta particles act as discrete obstacles in the amorphous matrix,restricting the highly localized shear band.This results in the formation of multiple shear bands around the Ta-rich particles,which lowers the stress concentration,allowing the shear band to propagate further and improve plasticity.
文摘Bulk metallic glass and their composites (BMGMCs) are a new class of materials which possess superior mechanical properties as compared to existing conventional materials. Owing to this, they are potential candidates for tomorrow’s structural applications. However, they suffer from poor ductility and little or no toughness which render them brittle and they manifest catastrophic failure under applied force. Their behavior is dubious, unpredictable and requires extensive experimentation to arrive at conclusive results. In present study, an effort has been made to design bulk metallic glass matrix composites by the use of modeling and simulation. A probabilistic cellular automaton (CA) model is developed and described in present study by author which is used in conjunction with earlier developed deterministic model to predict microstructural evolution in Zr based BMGMCs in additive manufacturing liquid melt pool. It is elaborately described with an aim to arrive at quantitative relations which describe process and steps of operations. Results indicate that effect of incorporating all mass transfer and diffusion coefficients under transient conditions and precise determination of probability number play a vital role in refining the model and bringing it closer to a level that it could be compared to actual values. It is shown that proposed tailoring can account for microstructural evolution in metallic glasses.
基金supported by the National Key Research and Development Plan(Grant Nos.2018YFA0703603,2021YFA0716302)Guangdong Major Project of Basic and Applied Basic Research,China(Grant Nos.2019B030302010,2020B1515120092)+2 种基金Guangdong Basic and Applied Basic Research Foundation,China(Grant Nos.2020B1515120092,2019B030302010)the National Natural Science Foundation of China(Grant Nos.52192602,52192603,51971092,11790291,and 61888102)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB30000000).
文摘The glass-forming ability and mechanical properties of metallic glasses and their composites are well known to be sensitive to the preparation conditions and are highly deteriorated by industrial preparing conditions such as low-purity raw materials and low vacuum.Here,we showed that a series of in-situ bulk metallic glass composites(BMGCs)which exhibit excellent ductility and segmental work hardening were successfully developed utilizing a high vacuum high-pressure die casting(HV-HPDC)technology along with industrial-grade raw materials.The tensile properties of these BMGCs are systematically investigated and correlated with the alloy microstructure.As compared with the copper mold suction casting method,the volume fraction difference of the dendrite phase for the BMGCs with the same composition is not significant when fabricated by the HV-HPDC,whereas the size of theβ-phase is generally larger.Insitu BMGCs with the composition of Ti_(48)Zr_(20)(V_(12/17)Cu_(5/17))19 Be 13 obtained by the HV-HPDC process show ductility up to 11.3%under tension at room temperature and exhibit a certain amount of work hardening.Two conditions need to be met to enable the BMGCs,which are prepared by vacuum die-casting to retain favorable ductility:(1)The volume fraction ofβphase stays below 62%±2%;(2)The equiaxed crystals with a more uniform size in the range of 5-10μm.Meanwhile,the results of the present study provided guidance for developing BMGCs with good ductile properties under industrial conditions.
基金supported by the National Natural Science Foundation of China(Grant Nos.52192604 and 52201181)the Key R&D Program of Hubei(No.2022BAA023).
文摘Additive manufacturing technology based on laser powder bed fusion(LPBF)offers a novel approach for fabricating bulk metallic glass(BMG)products without restriction in size and geometry.Nevertheless,the BMGs prepared by LPBF usually suffered from less plasticity and poorer fracture toughness as compared to their cast counterparts due to partial crystallization in heat-affected zones(HAZs).Since crystallization in HAZs is hard to avoid completely in LPBF BMGs,it is desirable to design a suitable alloy system,in which only ductile crystalline phase,instead of brittle intermetallics,is formed in HAZs.This unique structure could effectively increase the toughness/plasticity of the LPBF BMGs.To achieve this goal,a quaternary BMG system with a composition of Zr_(47.5)Cu_(45.5)Al_(5)Co_(2)is adopted and subjected to LPBF.It is found that nearly a single phase of B_(2)-ZrCu is precipitated in HAZs,while a fully amorphous phase is formed in molten pools(MPs).This B_(2)phase reinforced BMG composite exhibits excellent mechanical properties with enhanced plasticity and toughness.Furthermore,it is easy to modulate the mechanical properties by altering the amount of the B_(2)phase via adjusting the laser energy input.Finally,the best combination of strength,plasticity,and notch toughness is obtained in the BMG composite containing 27.4%B_(2)phase and 72.6%amorphous phase,which exhibits yield strength(σ_(s))of 1423 MPa,plastic strain(ε_(p))of 4.65%,and notch toughness(K_(q))of 53.9 MPa m 1/2.Furthermore,a notable strain-hardening is also observed.The improvement of plasticity/toughness and appearance of strain-hardening behavior are mainly due to the martensite phase transformation from the B_(2)phase to the Cm phase during plastic deformation(i.e.,the phase transformation-induced plasticity effect).The current work provides a guide for making advanced BMGs and BMG composites by additive manufacturing.
基金supported in part by the National Natural Science Foundation of China (No. 50571018)the National Basic Research Program of China (No. 2007CB613903)
文摘Starting with Zr of two different purities, Ti-based bulk metallic glasses (BMGs) with a nominal composition of Ti40Zr25Cu12Ni3Be20 were prepared. The effect of the addition of yttrium at levels of 0.2 at.%, 0.4 at.%, 0.5 at.%, 0.6 at.%, and 1 at.% on the glass forming ability (GFA) of the alloy has been investigated by means of metallography, X-ray diffraction, and differential scanning calorimetry. Experimental data in-dicates that high impurity content dramatically reduces the glass forming ability. Microalloying with 0.5 at.% Y is effective in suppressing the crystalline phase formation and alleviating the detrimental effect of oxygen in the low-purity alloy. On the contrary, in the alloy contain-ing high-purity element, the effective yttrium addition is less than 0.4 at.%. The results indicate that the beneficial effect of the optimum dopants is mainly due to scavenging the oxygen impurity via the formation of innocuous phase.
基金Iran University of Science and Technology for the financial support
文摘The formation of bulk metallic glasses(BMGs) in the ternary Zr(56) Co(28-x)Al(16) and quaternary Zr(56) Co(28-x)CuxAl16(x=2, 4, 5, 6, 7, mole fraction, %) glassy alloys was investigated via the copper mold suction casting method. The main purpose of this work was to locate the optimal BMG-forming composition for the quaternary Zr Co(Cu)Al alloys and to improve the plasticity of the parent alloy. The X-ray diffractometry(XRD), transmission electron microscopy(TEM) and differential scanning calorimetry(DSC) were used to investigate the glassy alloys structure and their glass forming ability(GFA). In addition, the compression test, microhardness, nano-indentation and scanning electron microscopy(SEM) were utilized to discuss the possible mechanisms involved in the enhanced plasticity achievement. The highest GFA among Cu-containing alloys was found for the Zr(56) Co(22) Cu6 Al(16) alloy, which was similar to that of the base alloy. Furthermore, the plasticity of the base alloy increased significantly from 3.3% to 6% for the Zr(56) Co(22) Cu)6 Al(16) BMG. The variations in the plasticity and GFA of the alloys were discussed by considering the positive heat of mixing within Cu and Co elements.
文摘Cu47Ti33Zr11Ni6Sn2Si1-based bulk metallic glass matrix composites reinforced with tungsten wires were fabricated by infiltration process at different temperatures (850, 900, 950 and 1000 °C) and time (10, 20 and 30 min) in a quartz or a steel tube. The mechanical tests were carried out by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the maximum strength and total strain of the composite are 1778 MPa and 2.8% fabricated in steel tube at 900 °C for 10 min, and 1582 MPa and 3.6% fabricated in quartz tube at 850 °C for 10 min, respectively.
文摘According to the Gibbs free energy difference between liquid and crystal,a thermodynamic glass-forming ability(GFA) parameter related to characteristic temperatures,onset crystallization temperature(Tx)and liquidus temperature(Tl),was proposed for evaluating the GFA of bulk metallic glasses(BMGs).The new parameter defined asω=Tl(Tl+Tx)/(Tx(Tl-Tx))has good correlation with the critical section thickness(Zc)of Ca-Mg-Cu BMGs.Being verified by the glasses data,including oxide glasses,which were used to validate the former GFA parameters,ωis one of the most reliable and applicable GFA parameters among Trg(=Tg/Tl), γ(=Tx/(Tl+Tg)),α(=Tx/Tl),δ(=Tx/(Tl-Tg),and so on.Finally,predicting GFA of Cu-Ag-Zr-Ti and Cu-Zr-Ti-Al BMGs usingωwas compared with the experimental results.
文摘The effect of the cooling slope on the structure of Zr-based metallic glass matrix composites was investigated by changing the cooling slope.The synthesis of bulk metallic glass composites was made by a process combining cooling slope casting and Cu mold casting for Zr66.4Nb6.4Cu10.5Ni8.7Al8 alloys.The results show that the semisolid slurry which consists of the spheroidal or rosette-type BCC crystals and the liquid phase which forms metallic glass phase can be formed by the cooling slope process in this alloy system.However,the semisolid slurry cannot reach to the mold.It is considered that higher viscosity of the liquid phase which forms metallic glass phase causes this result.Thus,parameters of the cooling slope have to be examined further.
基金supported by the National Natural Science Foundation of China (Nos50901012 and 50631010)the National Basic Research Priorities Program of China (No2007CB613902)
文摘Bulk metallic glass (BMG) formation was explored in the Fe-B-Si-Nb alloy system though combined use of the atomic cluster line approach and the minor alloying strategy. The basic ternary compositions in the Fe-B-Si system were determined by the intersection points of two cluster lines, namely, Fe-B cluster to Si and Fe-Si cluster to B. 3at% -4at% Nb was added to the quaternary Fe-B-Si-Nb alloy. The casting experiments revealed that good glass-forming ability (GFA) occurred at the (Fe73.4Si8.2B18.4)96Nb4 composition, and 3-mm diameter BMG samples were made. The glass transition temperature (Tg), crystallization temperature (Tx), and supercooled liquid region (△Tx=Tx-Tg) of this BMG were measured to be 866, 889, and 23 K, respectively. The BMG shows a high Vickers hardness of about Hv 1164, a Young's modulus of 180 GPa, and a good corrosion resistance in the solutions of 1 mol/L HCl and 3wt% NaCl.
文摘Bulk amorphous Cu52.5Ti30Zr11.5Ni6 and Cu53.1Ti31.4Zr9.5Ni6 alloys with a high glass forming ability can be quenched into single amorphous rods with a diameter of 5 mm, and exhibit a high fracture strength of 2 212 MPa and 2 184 MPa under compressive condition, respectively. The stress—strain curves show nearly 2% elastic strain limit, yet display no appreciable macroscopic plastic deformation prior to the catastrophic fracture due to highly localized shear bands. The present work shows clearly evidence of molten droplets besides well-developed vein patterns typical of bulk metallic glasses on the fracture surface, suggesting that localized melting induced by adiabatic heating may occur during the final failure event.
文摘The bulk Fe<sup>60 CoxZr<sup>10 Mo5W2B<sup>23-x (x=1, 3, 5, 7, 9) amorphous rods with diameters of 1.5 mm were successfully prepared by copper mold casting method with the low purity raw materials. The amorphous and crystalline states, and thermal parameters, such as the glass transition temperature (Tg), the initial crystallization temperature (Tx), the supercooled liquid region (ΔTx=Tx-Tg), the reduced glass transition temperature T<sup>rg (Tg/Tm, Tm: the onset temperature of melting of the alloy, and Tg/Tl, Tl: the finished temperature of melting of the alloy) were investigated by X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) analysis. Glass forming ability of Fe<sup>60 CoxZr<sup>10 Mo5W2B<sup>23-x (x=1,3,5,7,9) bulk metallic glasses has been studied. According to the results, the alloy (x=7) with the highest T<sup>rg (Tg/Tl=0.607, Tg/Tl=0.590) value, has the strongest glass forming ability among these alloys because its composition is near eutectic composition. The wide supercooled liquid region over 72 K indicates the high thermal stability for this alloy system. This bulk metallic glass exhibits quite high strength (Hv 1020). The success of production of the Fe-based bulk metallic glass with industrial materials is of great significance for the future progress of basic research and practical application.
基金This work was financially supported by the National Natural Science Foundation of China (No.50225103, 50471001, and 50631010).
文摘The formation and thermal stabilities of Cu46.25Zr46.25xAl7.5Erx (x=0 to 8) bulk metallic glasses (BMGs) were investigated. The addition of a small amount of Er (2at%) for replacing Zr effectively improves the glass-forming ability of Cu46.25Zr46.25Al7.5 alloy, and the glassy rod with a diameter of at least 12 mm can be formed. The glass transition temperature (Tg), temperature interval of su- percooled liquid region △Tx (=Tx-Tg), and reduced glass transition temperature Trg (=Tg/Tl) of Cu46.25Zr44.25Al7.5Er2 glassy alloy are 699 K, 62 K and 0.607, respectively.
基金Projects(50571092, 50601023) supported by the National Natural Science Foundation of China
文摘The effect of partial substitution of Al for Cu on the glass forming ability(GFA) and mechanical properties of Mg65Cu25-xAlxGd10 (x=0, 1, 3 and 5, molar fraction, %) alloys were studied by X-ray diffractometry(XRD), differential scanning calorimetry(DSC) and uniaxial compression test. The result reveals that GFA of the alloys changes slightly with increasing x from 0 to 3, and then abruptly decreases with x increasing up to 5. The plasticity can be greatly improved with appropriate substitution of Cu by Al (3%, molar fraction) in Mg65Cu25Gd10 bulk metallic glass, and the resultant fracture strength, total strain to failure, and plastic strain are 898 MPa, 2.19% and 0.2%, respectively.