Glass-forming ability and crystallization of Mg-Ni amorphous alloys with Y addition

Mg86.33Ni13.67-xYx(x=0, 1, 3, 6, 10) amorphous alloys were obtained by single-roller melt-spinning technique and the effect of Y addition on the glass forming ability(GFA), crystallization and micro-hardness of Mg-Ni alloys were studied. The results show that the GFA of Mg86.33Ni13.67-xYx(x=0, 1, 3, 6, 10) is improved successfully with the Y addition. The highest GFA appeares at x=6, while the reduced glass transition temperature (Trg) is 0.5225 and the supercooled liquid region(ΔTx) is 42.06 K; the position of the main diffraction halo is different for the alloys, and the maximum of the main diffraction halo of alloys with x=0, 1, 3 corresponds to the main peaks of a metastable fcc-Mg6Ni or fcc-Mg6Ni + Ni-Y intermetallic phases, and for the alloys with x=6, 10, it corresponds to Mg-Y and Ni-Y intermetallic phases; the micro-hardness of the alloys is improved with Y additions, and the highest micro-hardness is obtained at x=6 at.%, which is 960 MPa.

Amorphous forming ability of Co-X(X=Cr,Mo,W) magnetic thin films

Co-X （X=Cr, Mo, W） magnetic thin films were prepared by using DC magnetron sputtering, and their structures were examined by using X-ray diffraction （XRD）. The amorphous forming ability （AFA） of the three alloy systems was discussed based on thermodynamic calculation and experiments. The results show that the Co-Mo thin films exhibit the largest AFA among them, and the Co-W thin films are conditiondependent amorphous while the Co-Cr thin films are hard to be amorphous, which is consistent with the thermodynamic calculation. The difference in AFA for the alloys of these three systems is finally ascribed to three main factors： differences in electronegativity, electron density and atomic size between Co and X elements.

STRUCTURE AND GLASS FORMING ABILITY(GFA)OF AMORPHOUS ALLOYS

A new microstructure model is developed for amorphous alloys,so called Cluster medel, in which the amorphous phase is thought of composing of randomly distributed ordered clusters of different sizes.Thermodynamic calculation on this model deduces a parameter describing the glass forming ability of metallic alloys:α_c=(1-2.08/Φ_m)T_g/T_m,where T_g is gass transition temperature,T_m is the melting temperature,and Φ_m is entralpy change of melting.It is believed that easy glass forming alloy systems have larger values of a_c.This new criterion of GFA not only provides the theoretical background for several GFA criteria in the literature cited,but also can predict the GFA of many alloy systems more reasonably and accurately.

Evaluation of the amorphous-forming ability of M-Si-B ternary alloys using CALPHAD approach

A thermodynamic study has been carried out on M-Si-B (M=Fe, Ni) ternary systems. A regular solution approximation based on the sublattice model was adopted to describe the Gibbs energy for the individual phases in the binary and ternary systems. Thermodynamic parameters for each phase were evaluated by using the experimental data. These parameters enabled us to obtain reproducible calculations of the isothermal and vertical section diagrams. The amorphous-forming ability of M-Si-B ternary alloys has been evaluated by introducing thermodynamic quantities obtained from the phase diagram calculations into Davies-Uhlmann kinetic formulations. For the computation, the time-temperature- transformation (TTT) diagram, which gives the time necessary for the formation of the detectable amount of crystal during transformation, was obtained at a finite temperature. The critical cooling rate for amorphization could be defined as the minimum cooling speed that does not intersect the TTT curve and, hence, these critical cooling rates enable us to evaluate the glass-forming ability of M-Si-B ternary alloys. The driving force for the crystallization of the crystalline phase was derived, on the basis of the thermodynamic functions of each phase formulated by the present study. The calculated results showed good agreement with the experimental data on the compositional range of amorphization in these alloy systems.

Influence of flux treatment on the glass forming ability of Pd-Si binary alloys

Pd81Si19 amorphous alloys were prepared by combination methods of melt spinning and B2O3 flux treatment. A compari- son between the ribbons prepared from the fluxed ingots and the non-fluxed ones has been carried out. The result reveals that after fluxing treatment the glass transition temperature of the as-prepared glassy ribbons is reduced while the initial crystallization tem- perature is enhanced. It results in that the supercooled liquid region (defined as the difference between the initial crystallization tem- perature and the glass transition temperature) of the glassy alloy treated with fluxing technology has been increased from 31 to 42 K. This shows that fluxing technique can enhance the glass forming ability (GFA) of the binary alloy and improve the thermal stability of supercooled liquid of the glassy alloy.

Effect of Ni substitution on the formability and magnetic properties of Gd50Co50 amorphous alloy

A small amount of Ni was added into the binary Gd50Co50 amorphous alloy to replace Gd in order to obtain ternary Co50Gd50-xNx(x=1,2,and 3)amorphous alloys.Compared to the binary Gd50Co50 amorphous alloy,the Co50Gd50-xNx amorphous alloys show an enhanced Curie temperature(TC)with a weakened formability.The maximum magnetic entropy change(-Δ^Smpeak)of the Co50Gd50-xNx amorphous alloys is found to decrease with the increasing TC.The adiabatic temperature rise(ΔTad)of the Co50Gd47Ni3 amorphous alloy is superior to that of the Fe-based metallic glasses at room temperature.The variation of the TC and-Δ^Smpeak of the Gd50Co50 amorphous alloy with Ni addition,and the mechanism involved,were discussed.

Effects of rare-earth elements on the glass-forming ability and mechanical properties of Cu_(46)Zr_(47-x)Al_7M_x(M = Ce,Pr,Tb,and Gd) bulk metallic glasses

Cu46Zr47-xA17Mx （M = Ce, Pr, Tb, and Gd） bulk metallic glassy （BMG） alloys were prepared by copper-mold vacuum suction casting. The effects of rare-earth elements on the glass-forming ability （GFA）, thermal stability, and mechanical properties of Cu46Zr47-xA17Mx were investigated. The GFA of Cu46Zr47-xA17Mx （M = Ce, Pr） alloys is dependent on the content of Ce and Pr, and the optimal content is 4 at.%. Cu46Zr47-xA17Thx（X = 2, 4, and 5） amorphous alloys with a diameter of 5 mm can be prepared. The GFA of Cu46Zr47-xA17Gdx（x = 2, 4, and 5） increases with increasing Gd. Tx and Tp of all decrease. Tg is dependent on the rare-earth element and its content. ATx for most of these alloys decreases except the Cu46Zra2Al7Gd5 alloy. The activation energies △Eg, △Ex, and △Ep for the Cu46Zr42A17Gd5 BMG alloy with Kissinger equations are 340.7, 211.3, and 211.3 kJ/mol, respectively. These values with Ozawa equations are 334.8, 210.3, and 210.3 kJ/mol, respec- tively. The Cu46Zr45Al7Tb2 alloy presents the highest microhardness, Hv 590, while the Cu46Zr43A17Pr4 alloy presents the least, Hv 479. The compressive strength （at.f.） of the Cu46Zra3A17Gd4 BMG alloy is higher than that of the Cu46Zr43Al7Tb4 BMG alloy.

Glass-forming ability, microhardness, corrosion resistance, and dealloying treatment of Mg60.xCu40Ndx alloy ribbons

The influence of Nd addition on the glass-forming ability (GFA), microhardness, and corrosion resistance of Mg60−xCu40Ndx(x = 5, 10, 15, 20, and 25, at%) alloys were investigated by differential scanning calorimetry, Vickers-type hardness tests, and electrochemical methods. The results suggest that the GFA and microhardness of the amorphous alloys increase until the Nd content reaches 20at%. The corrosion potential and corrosion current density obtained from the Tafel curves indicate that the Mg35Cu40Nd25ternary alloy exhibits the best corrosion resistance among the investigated alloys. Notably, nanoporous copper (NPC) was synthesized through a single-step dealloying of Mg60−xCu40Ndx(x = 5, 10, 15, 20, and 25) ternary alloys in 0.04 mol·L−1H2SO4solution under free corrosion conditions. The influence of dealloying process parameters, such as dealloying time and temperature, on the microstructure of the ribbons was also studied using the surface diffusivity theory. The formation mechanism of dealloyed samples with a multilayered structure was also discussed. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Effect of Pd on GFA and Thermal Stability of Zr-based Bulk Amorphous Alloy

The effect of Pd addition on the glass-forming ability and thermal stability of the Zr55Al10Cu30Ni5-xPdx (x=0, 1, 3, 5 at. pct) alloys upon copper-mold casting has been investigated. The structure, thermal stability and microstructure were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM), respectively. It was identified that a new bulk amorphous alloy with the larger supercooled liquid region Tx of 100 K is obtained with substituting Ni by 1 at. pct Pd. Furthermore, the origins that thermal stability and GFA change with increasing of Pd have also beer discussed.

Glass forming ability of Zr-and Fe-based alloys at quenching from melts

The master alloy ingots (MAI) with the nominal composition Zr 52.5 Ti 5Cu 17.9 Ni 14.6 Al 10 and Fe 61 Co 7Zr 10 Mo 5W 2B 15 (at%) were prepared by arc melting in Ti gettered Ar atmosphere. The Zr based buttons of 6 mm and 9 mm in diameter were fully amorphous, but those of 13 mm in diameter experienced crystallization. The glass forming ability (GFA) of Fe based alloys was relatively lower, and the buttons obtained were fully crystallized. The microhardness of the Zr based buttons was about 500(Hv), and the Fe based rod obtained by injection technique exhibited a high Vickers hardness of 1329. In addition, an amorphous crystalline transition layers were observed in both the buttons and the rods.

Fragility and glass forming ability of Al-Ni-Ce alloy melts

The fragility of Al Ni Ce alloy melts with three kinds of different compositions, Al85Ni10Ce5, Al85Ni8Ce7, Al85Ni5Ce10(mole fraction, %), was studied using oscillating vessel viscometer and differential scanning calorimetry. Their fragility parameters obtained from experiments and theoretic calculation are: 238, 228 and 335 respectively. The results indicate that these three kinds of Al Ni Ce alloy melts are very fragile liquids, which kinetically show strong non Arrhenius behaviour in the Angell plot, so they have poor glass forming ability (GFA). The alloy melt Al85Ni5Ce10 has the largest fragility parameter among the three alloy melts. In the preparation of rapidly quenched amorphous ribbons, Al85Ni10Ce5 and Al85Ni8Ce7 can gain amorphous ribbons when the rotate speed of the roller reaches 800 r/min, while for Al85Ni5Ce10 it must exceed 1 000 r/min.

TiC对Fe_(55)Nb_(15)Ti_(15)Ta_(15)合金非晶形成能力、微观组织及热稳定性的影响

铁基非晶合金存在非晶形成能力低、室温塑性差等问题,极大地限制了其在工程中的应用。基于“近混合焓+有效原子尺寸差”非晶合金成分设计理念设计了Fe_(55)Nb_(15)Ti_(15)Ta_(15)全金属组元粉末,采用机械合金化球磨工艺成功制备出非晶态合金粉末,并研究了TiC陶瓷粉末的加入对Fe_(55)Nb_(15)Ti_(15)Ta_(15)合金粉末非晶形成能力、微观形貌和热稳定性的影响。结果表明:Fe_(55)Nb_(15)Ti_(15)Ta_(15)合金粉末具有较好的非晶形成能力和热稳定性,TiC陶瓷粉末均匀稳定的分布于Fe_(55)Nb_(15)Ti_(15)Ta_(15)非晶合金粉末中。添加质量分数15%TiC陶瓷粉末延缓了球磨过程中Fe_(55)Nb_(15)Ti_(15)Ta_(15)合金粉末的合金化和非晶化进程,降低了热稳定性,使得球磨后粉末粒度变小,分布范围变宽。该项工艺可制备出具有较大室温塑性的大块铁基非晶合金原始粉末。

Si添加对FeSiBPCu合金结晶行为、热稳定性和软磁性能的影响

针对Si元素含量对FeSiBPCu合金结构和性能的影响进行研究,提出利用Si元素置换B元素的方法来分析元素含量对合金结构和性能的影响。分别使用X射线衍射仪、差示扫描量热法、振动样品磁强计和扫描电子显微镜分析FeS-iBPCu系合金中Si元素含量变化对非晶形成能力、热稳定性和软磁性能的影响。实验结果表明,5种不同成分样品均表现出非晶结构,Si的加入有利于提高合金的非晶成形能力;铸态条带加热时均发生2次晶化,随着Si含量的增加,晶化起始温度第1次向低温区移动,第2次向高温区移动,2次晶化之间的温度区间明显扩大,增大了退火范围;淬态薄带饱和磁化强度随着Si元素的添加基本保持不变,最大值为149 emu·g^(-1);选择软磁性能较好的淬态Fe80Si6B10P3Cu1非晶薄带在不同温度下进行晶化退火处理10 min,温度超过730 K时开始析出纳米晶,随着退火温度升高,纳米晶析出密度增加,晶粒尺寸变大,退火后的非晶/纳米晶合金具有良好的软磁性能,表现出较高的饱和磁化强度(181 emu·g^(-1))。适量Si元素的添加有利于提高FeS-iBPCu合金的非晶形成能力和软磁性能。

Design of FeSiBPCu soft magnetic alloys with good amorphous forming ability and ultra-wide crystallization window

The Fe_(81.3)Si_(4)B_(13–x)PxCu_(1.7) soft magnetic alloys with high Cu and proper P elements addition were synthesized with the aim of ensuring the amorphous forming ability(AFA)while expanding the crystallization window(CW).It is found that the atomic ratio of P/Cu of∼3 is advantageous for AFA whereas a small amount of P addition promotes the precipitation ofα-Fe grains and excessive P addition induces surface crystallization behavior of the present alloys.High Cu concentration can expand the annealing temperature(Ta)window whereas proper P addition effectively expands the annealing time(ta)window.The Fe_(81.3)Si_(4)B_(13-x)PxCu_(1.7) soft magnetic alloy was successfully synthesized with a large Ta window of up to 130°C and ta window of 90 min,which is a breakthrough for nanocrystalline alloys with high saturation magnetization.Microstructure analysis reveals that the ultra-wide CW is related to the unique nucleation mechanism,that is,theα-Fe grains are precipitated attaching to the Cu or CuP clusters and enveloping the Cu clusters,resulting in the high number density ofα-Fe nanocrystals.The ultra-wide CW promises the potential material in flexibly choosing the annealing process according to the performance.

Comparative Study on Thermodynamical and Electrochemical Behavior of Al_(88)Ni_6La_6 and Al_(86)Ni_6La_6Cu_2 Amorphous Alloys

Two amorphous ribbons with the compositions of Al88Ni6La6 and Al86Ni6La6Cu2 were made using the melt-spun method,and their thermal response and electrochemical behavior were studied comparatively.Differential scanning calorimetry（DSC）and electrochemical polarization measurements indicated that Al86Ni6La6Cu2 exhibited slightly higher crystallization temperature（Tx）,lower melting point（Tl）and better corrosion resistance in 0.01 mol·L-1 NaCl alkaline solution.These results demonstrated that Cu（2%）addition could slightly promote the glass forming ability,but it could greatly improve the corrosion resistance of Al88Ni6La6 alloy in 0.01 mol·L-1 NaCl alkaline solution.

A comparative study of the structure and crystallization of bulk metallic amorphous rod Pr60Ni30Al10 and melt-spun metallic amorphous ribbon Al87Ni10Pr3

Pr-based bulk metallic amorphous （BMA） rods （Pr60Ni30Al10） and Al-based amorphous ribbons （Al87Ni10Pr3） have been prepared by using copper mould casting and single roller melt-spun techniques, respectively. Thermal parameters deduced from differential scanning calorimeter （DSC） indicate that the glass-forming ability （GFA） of Pr60Ni30Al10 BMA rod is far higher than that of Al87Ni10Pr3 ribbon. A comparative study about the differences in structure between the two kinds of glass-forming alloys, superheated viscosity and crystallization are also made. Compared with the amorphous alloy Al87Ni10Pr3, the BMA alloy Pr60Ni30Al10 shows high thermal stability and large viscosity, small diffusivity at the same superheated temperatures. The results of x-Ray diffraction （XRD） and transmission electron microscope （TEM） show the pronounced difference in structure between the two amorphous alloys. Together with crystallization results, the main structure compositions of the amorphous samples are confirmed. It seems that the higher the GFA, the more topological type clusters in the Pr-Ni-Al amorphous alloys, the GFAs of the present glass-forming alloys are closely related to their structures.

Amorphous in a Zr-IQC-DQC pseudo-ternary alloy system

A pseudo-ternary alloy system was constructed by combining an icosahedralquasicrystal (IQC), a decagonal quasicrystal (DQC), and Zr into one alloy system. Differentproportions of Zr were added to pseudo-binary alloy IQC_(80)DQC_(20) (mass fraction in %);Structural evolution in these alloys was discussed. An amorphous alloy composition was found in thissystem and a melt-spinning amorphous alloy was produced in this composition. Through DSC analysis,the amorphous alloy exhibits high glass forming ability comparable to that of the InoueZr_(65)Al_(7.5)Cu_(17.5)Ni_(10) amorphous alloy.

Fabrication of Ti-based Amorphous Composite and Biocompatibility Research

Ti-based alloy Ti64Zr5Fe6Si17Mo6Nb2 （At %） and Ti70Zr6Fe7Si17 （At %） ribbons with a width of 3-5 mm and thickness of about 80 um were fabricated by a single roller spun-melt technique. The feature of the alloy composition satisfies the three empirical rules. Amorphous structures of both alloys were confirmed by the X-ray diffraction pattern. To test the biocompatibility, both alloys were cultivated in the simulate body fluid （SBF）. After 15 days, the Ca phosphates depositions on alloys surfaces were gained. Moreover, n（Ca）/n（P） atom ratio of the deposition is about 1.6/1, which approaches to that of human bone—1.66/1, suggesting that both alloys were with a favorable biocompatibility.

Investigation of Glass Formability in Al-Co-Y Ternary System

The glass formation was investigated in the melt-spun Al-rich Al-Co-Y alloys by the microstructure evolution. The best glass former Al88Co5Y7 with the thickness of 230μm was found, and its glass forming ability （GFA） was higher than that of previously reported Al88Co4Y8 alloy. This result indicates that GFA is strongly sensitive to the alloy composition in the system. The phase selection method is an effective way to locate the optimum glass formation composition rather than Trg and △Tx parameters.

Amorphous-crystalline transition layers formation during quenching of Fe_(61)Co_7Zr_(10)Mo_5W_2B_(15) melt

New Fe-based multicomponent amorphous alloys have been developed recently based on empirical rules for large glass forming ability(GFA). In the present investigation, the master alloy ingot with the nominal composition of Fe 61Co 7Zr 10Mo 5W 2B 15(mole fraction, %) was prepared by arc-melting under Ti-gettered Ar atmosphere. The Fe-based buttons with different transverse cross sections were fabricated by arc-melting method, and the d 2.5 mm Fe-based rods were manufactured by injection technique. Characterization of the ingots and the parameters associated with the thermal stability were carried out by X-ray diffractometry(XRD) and high temperature differential scanning calorimeter(DSC), respectively. The interval of the supercooled liquid region is 39 K for the Fe-based alloy. The GFA of Fe-based alloys is relatively lower, to the buttons obtained are all crystallized. The Fe-based rod exhibites a high Vickers hardness up to HV 1 329. In addition, an amorphous-crystalline transition layers are observed in the rod. This transition zone is caused by unhomogeneous temperature distribution and relatively lower GFA for Fe-based alloys.