Structure and Magnetic Properties of Fe1-xCx Solid Solution Prepared by Mechanical Alloying

Supersaturated solid solutions Fe1-xCx （0≤x≤0.9 ） of wide composition range have been prepared by mechanical alloying process. Nanocrystalline phase was formed for 0 ≤ x ≤ 0.67 and a large grain phase for 0.75 ≤ x ≤ 0.9. The large fraction of graphite volume puts off formation of nanocrystalline phase for high carbon content. In the large grain phase, magnetization follows simple magnetic dilution, and eoereivity He is mainly due to dissolution of carbon at grain boundaries. In the nanocrystalline phase the alloying effect of carbon is revealed by a distinct reduction of average magnetic moment. The increasing lattice constant with increasing carbon content is observed for x ≤ 0.5, suggesting that the high carbon concentration may enhance diffusion of carbon into the Fe lattice. It shows a discontinuity in the Hc variation with a grain size D of nanocrystalline phase. For small grain D below the critical value, Hc increases with D. For a large grain D, Hc decreases with increasing D. The solubility limit of carbon in a-Fe extended by nanocry- stalline phase formation is discussed.

Evaluation of HEBM Mechanical Alloying of Al₂O₃—356/7075 Powder Mixture

Particle reinforced aluminium alloy metal matrix composites (MMC) have proven to be one of the advanced materials capable of replacing conventional structural alloys. However, the demand for such materials has been confined to high cost applications due to their complex processing. A preliminary mechanical alloying (MA) of metal powder with ce-ramic particulates by High Energy Ball Mill (HEBM) processing is a step of MMC manufacturing process. In this paper mechanical alloying of aluminium alloys A356 and 7075 powder with Al2O3 and SiC par-ticulates using two types of HEBM was investigated. The effect of dispersed phase strengthening mechanism on three aluminium grade alloys was evaluated by micro hardness measurement. Microstructure investigation confirms the achieved strengthening results. It was established that by measuring hardness of alloyed aluminium particles with low load reliable information on the alloying effect can be achieved.

Microstructure and Mechanical Properties of as Cast Aluminium Alloy 7075/Basalt Dispersed Metal Matrix Composites

This paper aims to study the effects of short basalt fiber reinforcement on the mechanical properties of cast aluminium alloy 7075 composites containing short basalt fiber of content ranging from 2.5 to 10 percent by weight in steps of 2.5 percent and fabricated using compo-casting technique. The objective is to investigate the process feasibility and resulting material properties such as young’s modulus, ductility, hardness & compression strength. The properties obtained are compared with those of as-cast that were manufactured under the same fabrication conditions. The results of this study revealed that, as the short basalt fiber content was increased, there were significant increases in the ultimate tensile strength, hardness, compressive strength and Young’s modulus, accompanied by a reduction in its ductility. Furthermore, the microstructure & facture studies were carried out using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) in order to establish relationships between the quality of the fiber/aluminium interface bond and hence to link with mechanical properties of the composites.

TiC颗粒增强FeCrCoMnNi基复合材料的微观组织与力学性能

采用机械球磨和放电等离子烧结制备了TiC颗粒增强FeCrCoMnNi高熵合金基复合材料,研究了TiC质量分数和烧结温度对复合材料组织性能的影响。结果表明,随着TiC质量分数的增加,复合材料中由C和Cr反应形成的M_(23)C_(6)碳化物的数量也增加,复合材料由面心立方基体、TiC和Cr_(23)C_(6)碳化物组成。1000℃烧结制备的复合材料中,当TiC质量分数在1%~9%时,陶瓷颗粒增强相在复合材料中的分布较为均匀。烧结温度对组织性能有较大影响,1000℃和1050℃烧结制备的复合材料组织均匀,具有较佳的力学性能。添加7%TiC的复合材料硬度和室温屈服强度分别是未添加TiC复合材料的2.5倍和3.0倍,这得益于TiC和Cr_(23)C_(6)碳化物硬质相的强化作用。

脱合金工艺对混杂增强非晶复合材料组织与性能的影响

基于金属熔体脱合金法制备了具有核壳混杂增强结构(核相为高熔点富Ta相,壳为B2-CuZr相)的[(Zr_(0.5)Cu_(0.5))_(92.5)Al_(7)Sn_(0.5)]_(0.95)Ta_(5)非晶复合材料,系统研究了不同脱合金工艺参数下非晶复合材料的显微组织及力学性能的演变规律。结果表明:脱合金温度和时间是控制富Ta相尺寸的关键参数。当反应温度过低或反应时间过短时,会造成富Ta相聚集、增强相分布不均匀;当反应温度过高或反应时间过长时,会导致富Ta相粗化。当脱合金反应时间为2 min、脱合金反应温度为1473 K时,非晶基体中富Ta相尺寸细小且弥散分布,并促进B2-CuZr相异质形核细化,得到了尺寸更细小、分布更均匀的核壳混杂增强结构。细小均匀的增强相可有效阻碍非晶基体中主剪切带的快速扩展,复合材料的力学性能得到大幅提高,断裂强度达到2439 MPa,塑性应变为11.6%。

难熔高熵合金研究进展

综述难熔高熵合金目前的研究现状,阐述难熔高熵合金成分设计,归纳包括金属元素和非金属元素对难熔高熵合金结构与性能的影响。另外描述不同制备方法下,难熔高熵合金的微观结构与力学性能,讨论难熔高熵合金基复合材料及其强化机制。对难熔高熵合金未来发展进行展望,并对其未来研究方向提出以下建议:通过不同相之间界面设计,多相协同增强难熔高熵合金;设计并优化难熔高熵合金成分,开发出室温易加工的难熔高熵合金;结合高通量计算方法,快速筛选出难熔高熵合金成分和微观结构;利用增材制造技术对难熔高熵合金组织与结构进行调控;对难熔高熵合金基复合材料进行构型化设计,均衡难熔高熵合金基复合材料的强塑性匹配。

INVESTIGATION ON MECHANICAL PROPERTIES OF ZN-AL/SIC PARTICULATE COMPOSITES

In order to improve the properties of ZA 27 and ZA4-3 zinc alloys and broaden their application ranges,SiC particlj1Ale composites, prepared by means of rheological casting technology, are investigated individually on their rT..t'llanical properties. The results of ne-cural strength, impact strensttl, compressive strength, hardness values and wear rate of the composites show that the addition of SiCp, leads to the increase of the compressive strength and hardness values at both room and higher temperature, and wear resistance of the materials, accompanying with the slight decrease of the fie-cural strength and sharp reduction of the impacttoughness. The factors affecting the mechanical properties of the composites are discussed in the paper.

Effects of Mg content on microstructure and mechanical properties of SiC_p/Al-Mg composites fabricated by semi-solid stirring technique

10%(volume fraction) SiCp/Al-Mg composites with different Mg contents were successfully fabricated by semi-solid mechanical stirring technique under optimum processing conditions.Effects of Mg content on microstructure and mechanical properties were studied by scanning electron microscopy(SEM),X-ray diffractometry(XRD) and transmission electron microscopy(TEM).The results indicate that SiC particles disperse homogeneously in Al-Mg matrix and interfacial reaction between Al matrix and SiC particles is effectively controlled.Distribution of SiCp reinforcement and interfacial bonding are improved by adding Mg.Additionally,the mechanical properties of composites are remarkably improved with the Mg content increasing.

Processing, characterization, room temperature mechanical properties and fracture behavior of hot extruded multi-scale B_4C reinforced 5083 aluminum alloy based composites

Microstructural characteristics and mechanical behavior of hot extruded Al5083/B4C nanocomposites were studied.Al5083and Al5083/B4C powders were milled for50h under argon atmosphere in attrition mill with rotational speed of400r/min.For increasing the elongation,milled powders were mixed with30%and50%unmilled aluminum powder(mass fraction)with meanparticle size of>100μm and<100μm and then consolidated by hot pressing and hot extrusion with9:1extrusion ratio.Hot extrudedsamples were studied by optical microscopy,scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),transmission electron microscopy(TEM),tensile and hardness tests.The results showed that mechanical milling process andpresence of B4C particles increase the yield strength of Al5083alloy from130to566MPa but strongly decrease elongation(from11.3%to0.49%).Adding<100μm unmilled particles enhanced the ductility and reduced tensile strength and hardness,but usingthe>100μm unmilled particles reduced the tensile strength and ductility at the same time.By increasing the content of unmilledparticles failure mechanism changed from brittle to ductile.

Microstructure and mechanical properties of in-situ TiB_2/A356 composites and a prediction model of yield strength

The in-situ TiB2/A356 composites were successfully synthesized through the mixed salt reaction method. The advantage of this technique was that the particle sizes and morphology can be controlled by the melt reaction. Therefore, the technique can be designed to obtain expected properties, such as high strength at high and room temperatures, high damping capacity, high modulus and good fatigue life. Results showed that in the as-cast state of A356 alloy and TiB2/A356 composites, the eutectic Si phase is normally in the needle shape, and TiB2 particles are mostly in the cubic or near spherical shape, with the size ranging from 30 to 500 nm uniformly distributed in the grains. Also, TiB2 particle clusters are observed in composites. With an increase in TiB2 particles, the average grain size of composites decreases both in as-cast and T6 state. It is found that both the yield stength and ultimate tensile strength increase with an increase in the TiB2 volume fraction. On the contrary, the elongation reduces with the addition of TiB2 particles. Based on the experimental results and Clyne＇s report, a revised model related to particle strengthening mechanism was proposed to fairly predict yield strengths of TiBJA356 composites. The satisfactory agreement between the calculated values and experimental data reported in the literature was obtained.

Mechanical properties and friction behaviors of CNT/AlSi_(10)Mg composites produced by spark plasma sintering

The mechanical properties and friction behaviors of CNT/AlSi10Mg composites produced by spark plasma sintering (SPS) were investigated. The results showed that the densities of the sintered composites gradually increased with increasing sintering temperature and that the highest microhardness and compressive strength were achieved in the specimen sintered at 450A degrees C. CNTs dispersed uniformly in the Al-Si10Mg matrix when the addition of CNTs was less than 1.5wt%. However, when the addition of CNTs exceeded 1.5wt%, the aggregation of CNTs was clearly observed. Moreover, the mechanical properties (including the densities, compressive strength, and microhardness) of the composites changed with CNT content and reached a maximum value when the CNT content was 1.5wt%. Meanwhile, the minimum average friction coefficient and wear rate of the CNT/AlSi10Mg composites were obtained with 1.0wt% CNTs.

Mechanical and corrosion properties of graphene nanoplatelet–reinforced Mg–Zr and Mg–Zr–Zn matrix nanocomposites for biomedical applications

Magnesium(Mg)-based biomaterials have gained acceptability in fracture fixation due to their ability to naturally degrade in the body after fulfilling the desired functions.However,pure Mg not only degrades rapidly in the physiological environment,but also evolves hydrogen gas during degradation.In this study,Mg0.5Zr and Mg0.5ZrxZn(x=1–5 wt.%)matrix nanocomposites(MNCs)reinforced with different contents(0.1–0.5 wt.%)of graphene nanoplatelets(GNP)were manufactured via a powder metallurgy technique and their mechanical and corrosion properties were evaluated.The increase in GNP concentration from 0.2 wt.%to 0.5 wt.%added to Mg0.5Zr matrices resulted in decreases in the compressive yield strength and corrosion resistance in Hanks’Balanced Salt Solution(HBSS).On the other hand,a higher concentration(4–5 wt.%)of Zn added to Mg0.5Zr0.1GNP resulted in an increase in ductility but a decrease in compressive yield strength.Overall,an addition of 0.1 wt.%GNPs to Mg0.5Zr3Zn matrices gave excellent ultimate compressive strength(387 MPa)and compressive yield strength(219 MPa).Mg0.5Zr1Zn0.1GNP and Mg0.5Zr3Zn0.1GNP nanocomposites exhibited 29%and 34%higher experimental yield strength,respectively,as compared to the theoretical yield strength of Mg0.5Zr0.1GNP calculated by synergistic strengthening mechanisms including the difference in thermal expansion,elastic modulus,and geometry of the particles,grain refinement,load transfer,and precipitation of GNPs in the Mg matrices.The corrosion rates of Mg0.5Zr1Zn0.1GNP,Mg0.5Zr3Zn0.1GNP,Mg0.5Zr4Zn0.1GNP,and Mg0.5Zr5Zn0.1GNP measured using potentiodynamic polarization were 7.5 mm/y,4.1 mm/y,6.1 mm/y,and 8.0 mm/y,respectively.Similarly,hydrogen gas evolution tests also demonstrated that Mg0.5Zr3Zn0.1GNP exhibited a lower corrosion rate(1.5 mm/y)than those of Mg0.5Zr1Zn0.1GNP(3.8 mm/y),Mg0.5Zr4Zn0.1GNP(1.9 mm/y),and Mg0.5Zr5Zn0.1GNP(2.2 mm/y).This study demonstrates the potential of GNPs as effective nano-reinforcement particulates for improving the mechanical and corrosion properties of Mg–Zr–Zn matrices.

金属长丝复合导电纱的纺制与性能

为了探讨金属长丝在纺织上的应用,选用铜镁合金长丝、金属铜长丝与不锈钢长丝,利用赛络菲尔和赛络纺工艺制备金属长丝复合导电纱,对比测试了不同产品的力学性能和电热性能。对照FZ/T 12071—2021《导电纱线》产品标准,复合导电纱的断裂强度达到相应技术要求,导电性能达到A类产品要求。结果表明:金属长丝复合导电纱具有优良的定伸长循环拉伸、定负荷循环拉伸性能;金属铜长丝、铜镁合金长丝较不锈钢长丝具有更为优良的电热性能。通过复合纱的设计和纺制,金属长丝导电纱力学性能达标、电热性能优良,可以用于开发功能纺织产品。

铝合金表面Ni基复合涂层制备机理及摩擦性能

为提高铝合金在航空航天应用中的表面抗磨性能,采用机械球磨方法在其表面制备了Ni-Al和3种不同W含量的Ni-Al-W复合涂层.研究表明:四种复合涂层组织均匀分布,厚度约为50~100μm.随着W含量的增加颗粒的韧性变形面逐渐减少.经过热处理后,Ni-Al复合涂层中有Al 3 Ni和Al_(3)Ni_(2)金属间化合物生成,但其剩余粉末中仅有Al_(3)Ni_(2)生成,并且无细粉剩余.3种Ni-Al-W复合涂层和粗粉中有AlNi和Al_(3)Ni_(2)生成,细粉中Al_(3)Ni_(2)金属间化合物随W含量的增加逐渐消失.复合涂层显微硬度随W含量的增加有所增加,含W涂层摩擦系数略高于铝合金基体和Ni-Al复合涂层,处于0.6~0.75,但其磨损率远低于基体铝合金和Ni-Al复合涂层,约为0.2×10^(-3)~0.4×10^(-3)mm 3/(N·m),并且随W含量的增加略有降低.铝合金表面Ni-Al-W复合涂层的制备有效提升了铝合金表面的抗磨性能.

Influence of recycled carbon fiber addition on the microstructure and creep response of extruded AZ91 magnesium alloy

In this study,the recycled short carbon fiber(CF)-reinforced magnesium matrix composites were fabricated using a combination of stir casting and hot extrusion.The objective was to investigate the impact of CF content(2.5 and 5.0 wt.%)and fiber length(100 and 500μm)on the microstructure,mechanical properties,and creep behavior of AZ91 alloy matrix.The microstructural analysis revealed that the CFs aligned in the extrusion direction resulted in grain and intermetallic refinement within the alloy.In comparison to the unreinforced AZ91 alloy,the composites with 2.5 wt.%CF exhibited an increase in hardness by 16-20%and yield strength by 5-15%,depending on the fiber length,while experiencing a reduction in ductility.When the reinforcement content was increased from 2.5 to 5.0 wt.%,strength values exhibited fluctuations and decline,accompanied by decreased ductility.These divergent outcomes were discussed in relation to fiber length,clustering tendency due to higher reinforcement content,and the presence of interfacial products with micro-cracks at the CF-matrix interface.Tensile creep tests indicated that CFs did not enhance the creep resistance of extruded AZ91 alloy,suggesting that grain boundary sliding is likely the dominant deformation mechanism during creep.

High-temperature Mechanical Properties and Dynamic Recrystallization Mechanism of in situ Silicide-reinforced MoNbTaTiVSi Refractory High-entropy Alloy Composite

The hypoeutectic composite material composed of BCC phase and in situ precipitated Ti_(5)Si_(3) was prepared by adding Si into MoNbTaTiV high-entropy alloy.The obvious oriented in situ Ti_(5)Si_(3) phase formed eutectic phase with BCC phase in the inter-dendritic area,which leads to excellent properties of the composite.The alloy exhibits ultra-high yield stress of 718 MPa at 1200℃ and obvious compression plasticity.After reaching the maximum strength,dynamic recovery(DRV)and dynamic recrystallization(DRX)caused soften phenomena.The DRX mechanism of the dual-phase eutectic structure is analyzed by electron backscatter diffraction.The DRX of the BCC phase conforms to the discontinuous DRX and continuous DRX mechanisms,while the Ti_(5)Si_(3) phase has a geometric DRX mechanism in addition to the above two mechanisms.The high performance of this composite has enough potential high-temperature applications such as nuclear and aero engine.

Mechanical behavior and deformation mechanism of shape memory bulk metallic glass composites synthesized by powder metallurgy

The synthesis of martensitic or shape-memory bulk metallic glass composites(BMGCs)via solidification of the glass-forming melts requires the meticulous selection of the chemical composition and the proper choice of the processing parameters in order to ensure that the glassy matrix coexists with the desired amount of austenitic phase.Unfortunately,a relatively limited number of such systems,where austenite and glassy matrix coexist over a wide range of compositions,is available.Here,we study the effective-ness of powder metallurgy as an alternative to solidification for the synthesis of shape memory BMGCs.Zr_(48)Cu_(36)Al_(8)Ag_(8)matrix composites with different volume fractions of Ni_(50.6)Ti_(49.4)are fabricated using hot pressing and their microstructure,mechanical properties and deformation mechanism are investigated employing experiments and simulations.The results demonstrate that shape-memory BMGCs with tun-able microstructures and properties can be synthesized by hot pressing.The phase stability of the glass and austenitic components across a wide range of compositions allows us to examine fundamental as-pects in the field of shape memory BMGCs,including the effect of the confining stress on the martensitic transformation exerted by the glassy matrix,the contribution of each phase to the plasticity and the mechanism responsible for shear band formation.The present method gives a virtually infinite choice among the possible combinations of glassy matrices and shape memory phases,expanding the range of accessible shape memory BMGCs to systems where the glassy and austenitic phases do not form simul-taneously using the solidification route.

Laser powder bed fusion of NiTiFe shape memory alloy via premixed powder:microstructural evolution,mechanical and functional properties

High-cost pre-alloyed powder is the bottleneck problem that limits the widespread application of additivemanufactured shape memory alloys.In this work,the lowcost ternary NiTiFe shape memory alloy is fabricated by laser powder bed fusion(LPBF)technique via mechanically mixed pre-alloy NiTi powder and varying contents pure Fe powder(1,2,3 wt%).All NiTiFe alloys show a relative density of up to 99.8%by optimizing the LPBF processing parameters.Owing to the heterogeneous nucleation effect of micron-sized Fe particles,both grain refinement and texture weakening are generated in the NiTiFe alloys,accompanied by the reduction of dislocation density.For the room-temperature mechanical properties,the NiTi-3Fe alloy shows the highest microhardness of HV370,but the fracture strength and elongation reduce to1701 MPa and 23%simultaneously.The evolution of mechanical properties is attributed to the high internal defects,low dislocation density and the incoherent oxide.Moreover,the NiTi-3Fe alloy shows the quasi-linear superelasticity behavior;the superelastic recoverable strain of NiTi-1Fe and NiTi-2Fe decreased with the increase in Fe content.This study provided a new-fangled insight for the development of multi-component NiTi-based shape memory alloys by additive manufacturing.

Fabrication and characterization of stir casting AA6061-31%B_4C composite

A sophisticated stir casting route to fabricate large scale AA6061-31%B4C composite was developed. Key process parameters were studied, microstructure and mechanical properties of the composite were investigated. The results indicated that vacuum stirring/casting, B4C/Mg feeding and ingots cooling were essential to the successful fabrication of AA6061-31%B4C composite. Chemical erosion examination verified the designed B4 C content; X-ray fluorescence spectrometer（XFS） showed the chemical composition of Mg and Si in the matrix conformed to industry standards; scanning electronic microscope（SEM） and X-ray diffraction（XRD） revealed that B4 C particles were evenly distributed in the composites with well dispersed Mg2Si precipitates. Tensile testing results showed that the AA6061-31%B4C composite had a tensile strength of 340 MPa, improved by 112.5% compared with AA1100-31%B4C composite, which is attributed to the enhanced strength of the matrix alloy.