Microstructure and mechanical properties of Mg-4.0Zn-0.5Ca alloy

A new kind of Mg-4.0 wt.%Zn-0.5 wt.%Ca alloy is fabricated by casting and hot extrusion for used as a high performance structure material as well as a biomaterial. In the as-cast alloy, the average grain size of the α-Mg is 120-150 µm and the precipitated second phases are distributed uniformly in α-Mg grains. The as-cast Mg-4.0 wt.%Zn-0.5 wt.%Ca alloy shows a good balance between the tensile strength (211 MPa) and ductility (17% in elongation). After hot extrusion at 593 K, the second phase is greatly refined and the average grain size of the α-Mg is reduced to 8-12 μm which is resulted from dynamic re-crystallization during hot extrusion. In this case, it exhibits a high tensile strength (273 MPa) and a high ductility (34% in elongation) at room temperature.     

Effect of Zr on the microstructure, mechanical properties and corrosion resistance of Mg–10Gd–3Y magnesium alloy

The influence of Zr on the microstructure, mechanical properties and corrosion resistance of Mg–10Gd–3Y (wt.%) magnesium alloy was investigated. The grain size of alloys decreased with Zr content from 0% to 0.93% (wt.%). The addition of Zr greatly improved the ultimate tensile strength (UTS) and the elongation (EL), while slightly improved the tensile yield strength (TYS). The UTS and the EL of the alloy containing 0.93% Zr increased by 125.8 MPa and 6.96% compared with base alloy, respectively. The corrosion resistances were found to decrease with Zr content from 0% to 0.42% and then increase from 0.42% to 0.93%. The differences in the sizes and distributions of the Zr-rich particles have significant effects on the corrosion behaviors. The alloy with 0.42% Zr addition revealed the optimum combination of mechanical properties and corrosion resistance.     

Microstructure and mechanical properties of as-cast Mg-4Zn-0.5Zr-0.2Cu-0.2Ce alloy

In this study, an approach is proposed to improve the microstructure and mechanical properties of Mg-4Zn-0.5Zr alloy by combining trace Cu and rare earth Ce addition. The results showed that Cu and Ce additions led to obvious grain refinement and the formation of Mg-Zn-Cu and Mg-Zn-Ce phases. The Mg-Zn-Ce phase was identified to have an orthorhombic structure. The length of the [0001]_α rods in the Cu-containing alloys remarkably decreased. The yield strength increased slightly after Cu and Ce co-addition, which was attributed to grain refinement and precipitation strengthening. The coarse Mg-Zn-Ce phase distributed at the grain boundaries would reduce the ductility by promoting crack propagation during tensile processes.     

Microstructure and enhanced mechanical properties of an Mg-10Gd-2Y-0.5Zr alloy processed by cyclic extrusion and compression

The evolution of microstructure and texture of an extruded GW102K Mg alloy processed by cyclic extrusion and compression (CEC) at 450 °C were investigated. Tensile tests were performed at room temperature and strain rate 5 × 10⁻³ s⁻¹. The results show that the microstructure was effectively refined, and the initial fiber texture became disintegrated and developed a new texture after 14 CEC passes. It was found that the strength and ductility were simultaneously increased compared with the as-extruded alloy. In particular, the elongation and yield strength were related in a line relationship having a positive slope. As the texture changed and texture intensity decreased, substantial grain refinement was observed. The hard second-phase particles were considered to be responsible for the uncommon properties of the GW102K alloy processed by CEC.     

均匀化处理对Mg-13Gd-3.5Y-2Zn-0.5Zr镁合金组织和力学性能的影响

对Mg-13Gd-3.5Y-2Zn-0.5Zr镁合金铸锭进行均匀化处理,温度为505～525℃,时间为4～24h,并采用光学显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)和万能材料试验机等检测手段分析均匀化处理前后合金微观组织和力学性能的变化。结果表明:均匀化处理后,原始组织中网状分布共晶化合物转化成晶界处不连续分布的块状LPSO相,离散分布的方块状富稀土相溶解。力学性能测试显示,铸态镁合金的抗拉强度为172.9MPa,伸长率为1.8%,经过均匀化处理后合金的力学性能得到提高,在515℃/16h均匀化制度下,合金室温抗拉强度为212.3MPa,伸长率为3.1%;在200℃下抗拉强度为237.2MPa,伸长率为9.7%,性能达到最佳。断口扫描显示,铸态合金是以撕裂棱与解理台阶为主的解理脆性断裂,均匀化处理后的合金中出现小而浅的韧窝,但仍然是以解理台阶为主的准解理断裂,塑性提高有限,长程有序相可成为裂纹的萌生源。     

Microstructure and mechanical properties of an indirect-extruded Mg-8Sn-1Al-1Zn alloy

The microstructure and mechanical properties of an indirect-extruded Mg-8Sn-1Al-1Zn (TAZ811) alloy were investigated and compared with those of a commercial Mg-3Al-1Zn (AZ31) alloy. In the extruded condition, the TAZ811 alloy shows a much smaller grain size but a stronger basal texture than the AZ31 alloy. In addition, the TAZ811 alloy contains fine Mg₂Sn particles in the microstructure, whereas the AZ31 alloy reveals relatively coarse and sparse Al-Mn particles. The TAZ811 alloy showed tensile and compressive strengthening as well as a reduction in yield asymmetry between tension and compression, which is mainly due to grain refinement and the presence of fine Mg₂Sn particles.     

Investigation on microstructure and mechanical properties of Ti14 alloy after semisolid deformation

Abstract

This study details the development of microstructure of Ti14 alloy as a function of the forging temperature and forging ratio in semisolid state and influence of resulting microstructure on the mechanical properties. The results reveal that dynamic recrystallisation occurred during semisolid forging, and the grain refinement was attained. Grain size increased in the forging temperature and decreased in the forging ratio. High ultimate tensile strengths and low elongation have been achieved after semisolid forging. The strength decreased with increasing forging temperature, while the ductility increased with increasing forging ratio. The relative contributions of tensile properties were attributed to the varieties of grain size obtained by thixoforging.     

Elevated-temperature plasticity and mechanical properties of a rare earth-modified Mg-Zn-Al alloy

The elevated-temperature plasticity and flow behavior of an Er-modified, heat-resistant ZA73 alloy was evaluated by thermal simulation. The results showed that the addition of Er to ZA73 alloy notably improves the deformability and higher strain rate and temperature favors hot deformation. Bars with sound surface quality were successfully extruded at 350 °C and a strain rate of ~ 0.1 s^− 1. Furthermore, dynamic precipitation of nano-sized spherical τ phase was found to occur uniformly in the α-Mg matrix during hot extrusion, which is considered helpful to both strength and plasticity enhancement. The yield strength and ultimate tensile strength of the as-extruded bars reached 240-265 MPa and 355-360 MPa, respectively, while maintaining a large elongation rate of 18-19.5%.     

Effects of Sn addition on as-cast microstructure, mechanical properties and casting fluidity of ZA84 magnesium alloy

The effects of Sn addition on the as-cast microstructure, mechanical properties and casting fluidity of the ZA84 magnesium alloy are investigated. The results indicate that adding 0.5–2.0 wt.%Sn to the ZA84 alloy not only can result in the formation of Mg₂Sn phase but also can refine the Mg₃₂(Al, Zn)₄₉ phase and suppress the formation of Mg₃₂(Al, Zn)₄₉ phase, and with the increase of Sn amount from 0.5 wt.% to 2.0 wt.%, the morphology of Mg₃₂(Al, Zn)₄₉ phase gradually changes from coarse continuous and/or quasi-continuous net to relatively fine quasi-continuous and/or disconnected shapes. In addition, adding 0.5–2.0 wt.%Sn to the ZA84 alloy can improve the tensile and creep properties, and casting fluidity of the alloy. Among the Sn-containing ZA84 alloys, the ZA84 alloy added 1.0 wt.%Sn exhibits the best ultimate tensile strength, elongation and casting fluidity while the ZA84 alloy added 2.0 wt.%Sn has the best yield strength and creep properties.     

Balancing the strength and ductility of Mg-6Zn-0.2Ca alloy via sub-rapid solidification combined with hard-plate rolling

In this study,we successfully prepared a Mg-6Zn-0.2Ca alloy by utilizing sub-rapid solidification (SRS)combined with hard-plate rolling (HPR),whose elongation-to-failure increases from ～17 ％ to ～23 ％without sacrificing tensile strength (～290 MPa) compared with its counterpart processed via conven-tional solidification (CS) followed by HPR.Notably,both samples feature a similar refined grain structure with an average grain size of ～2.1 and ～2.5 μm,respectively.However,the high cooling rate of ～ 150 K/s introduced by SRS modified both the size and morphology of Ca2Mg6Zn3 eutectic phase in comparison to those coarse ones under CS condition.By subsequent HPR,the Ca2Mg6Zn3 phase was further refined and dispersed uniformly by severe fragmentation.Specially,the achieved supersaturation containing exces-sive Ca solute atoms due to high cooling rate was maintained in the SRS-HPR condition.The mechanisms that govern the high ductility of the SRS-HPR sample could be ascribed to following reasons.First,refined Ca2Mg6Zn3 eutectic phase could effectively alleviate or avoid the crack initiation.Furthermore,excessive Ca solute atoms in α-Mg matrix result in the yield point phenomenon and enhanced strain-hardening ability during tension.The findings proposed a short-processed strategy towards superior performance of Mg-6Zn-0.2Ca alloy for industrial applications.     

Effects of Zn on the microstructure, mechanical properties, and damping capacity of Mg-Zn-Y-Zr alloys

The influences of Zn on the microstructure, mechanical properties, and damping capacity of as-extruded (Mg-5%Y-0.6%Zr)_1−xZn_x (x = 2%, 4%, 6%, mass fraction) alloys were investigated by optical microscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, tensile testing, and dynamic mechanical analysis (DMA). The phase composition and microstructure of the alloys displayed evident variations with changes in Zn content. When the mass fraction of Zn changed from 2% to 6%, the phases mainly consisted of a long period stacking ordered (LPSO) X-phase (Mg₁₂YZn) and a W-phase (Mg₃Y₂Zn₃). Comparison of the mechanical properties and damping capacities of the different phases showed that the X-phase benefits the mechanical properties of the alloy without drastic impairment to their damping capacities. The damping capacities are discussed in terms of the Granato-Lücke theory and G-L plots.     

Microstructural evolution,mechanical properties and corrosion behavior of as-cast Mg-5Li-3Al-2Zn alloy with different Sn and Y addition

Influences of Sn and Y on the microstructure,mechanical properties,and corrosion behavior of as-cast Mg-5Li-3Al-2Zn (LAZ532) alloy were investigated.The addition of Sn and Y refines grains and results in the formation of Mg2Sn and Al2Y phases,thus improving the mechanical properties of alloy by second phase strengthening and grain refinement strengthening.As-cast LAZ532 alloy shows typical filiform corrosion morphology,and the addition of Sn and Y does not change the corrosion mode of alloy.Ascast LAZ532-0.8Sn-1.2Y alloy shows excellent mechanical properties with yield strength of 166.2 MPa,ultimate tensile strength of 228.6 MPa and elongation of 14.8 ％,and exhibits the best corrosion resistance with the smallest corrosion current density and the lowest anodic dissolution rate.     

Effect of Ca and Sr additions on high temperature and corrosion properties of Mg-4Al-2Sn based alloys

This study examined the effects of Ca and Sr addition on the creep and corrosion properties of Mg-Al-Sn based alloys with the aim of developing new Mg-Al-Sn-x alloys for automotive powertrain applications. The materials were cast using the squeeze casting process to obtain a dense microstructure without pores. Creep tests were carried out at a constant temperature between 150 °C and 200 °C and a constant applied stress between 50 and 80 MPa until the minimum creep rate had been reached. Potentiodynamic and immersion tests were carried out to evaluate corrosion properties of the alloys. The creep and corrosion resistance were improved by adding Ca and Sr.     

Effect of addition of Al-Si eutectic alloy on microstructure and mechanical properties of Mg-12wt%Li alloy

Mg-12Li, Mg-12Li-3(Al-Si), Mg-12Li-7(Al-Si) and Mg-12Li-9(Al-Si) alloys (all in wt%) were fabricated by high frequency vacuum induction melting in a water cooled copper crucible. After subsequently hot-rolling and annealing, their microstructure and mechanical properties were investigated. Experimental results show that mechanical properties of Mg-12Li alloy were significantly improved by the addition of Al-Si eutectic alloy. Mg-12Li-7(Al-Si) alloy shows the highest strength of 196 MPa of the investigated alloys, which is about 1.8 times of the strength of Mg-12Li alloy, and maintains high elongation of 27%. The improved mechanical property with addition of Al and Si in the eutectic proportion into Mg-12Li alloy was attributed to the solution strengthening effect of Al and precipitation hardening effect from AlLi and Mg₂Si precipitates.     

时效温度对Mg-12Gd-3Y-1Sm-0.5Zr合金组织和力学性能的影响

采用X射线衍射、光学显微镜、透射电子显微镜、显微硬度和拉伸性能测试等手段,研究时效热处理温度对Mg-12Gd-3Y-1Sm-0.5Zr合金组织和性能的影响。结果表明,Mg-12Gd-3Y-1Sm-0.5Zr合金在200,250℃和300℃峰时效时,晶粒大小随时效温度的升高而逐渐增大,晶内颗粒状的第二相数量增多,硬度峰值出现的时间逐渐缩短。合金时效温度在200,250℃时,析出相为β′相,时效温度在300℃时,析出相为β相。合金在250℃峰时效时力学性能最优。在200,250℃峰时效热处理的合金在从室温到200,250℃和300℃拉伸过程中抗拉强度随拉伸温度的升高先升高后降低,出现了抗拉强度反常温度效应,而在300℃峰时效热处理后的合金未出现该反常现象。     

Alloying and thermal behaviour of CoCrFeNiMn0.5Ti0.5 high-entropy alloy synthesised by mechanical alloying

An inequi-atomic CoCrFeNiMn_0.5Ti_0.5 high-entropy alloy (HEA) was synthesised by mechanical alloying. The structural and morphological evolution of the alloy powder during the mechanical alloying process and the thermal behaviour of 60?h ball-milled HEA powder were investigated systematically. A simple body-centred cubic solid solution HEA structure was obtained when the blended powder was ball-milled longer than 36?h. A 60?h ball-milled powder had an average particle size of 3?μm and consisted of hard agglomerated crystalline particles with a crystal size of <?20?nm. The body-centred cubic phase transformed into a face-centred cubic phase when the powder was annealed for 1?h at a temperature of 700°C; the liquidus point of the face-centred cubic phases was 1402.8°C.     

Microstructural evolution,mechanical properties and corrosion mechanisms of additively manufactured biodegradable Zn-Cu alloys

Additively manufactured(AM)biodegradable zinc(Zn)alloys constitute an important branch of orthope-dic implants because of their moderate degradation properties and bone-mimicking mechanical proper-ties.In this paper,the microstructural evolution and corrosion mechanisms of zinc-copper(Zn-Cu)alloys prepared by the laser-powder-bed-fusion(L-PBF)additive manufacturing method were investigated.Al-loying with Cu significantly increases the ultimate tensile strength(UTS)of unalloyed Zn,but the UTS and ductility of unalloyed Zn and Zn-2Cu decrease with increasing laser energy density.Unalloyed Zn has a dendritic microstructure,while Zn-2Cu alloy has a peritectic microstructure.The formation of round peri-tectic grains is due to the low-temperature gradient of unalloyed Zn during the AM.The Zn-2Cu samples exhibited higher corrosion rates,addressing the problem of slow degradation of unalloyed Zn.The grain size distribution influences the corrosion behavior of the material.It enhances the corrosion rates of ma-terials with fine grains in a non-passivating environment.However,the 100％extracts of Zn-2Cu samples exhibited greater values of cellular activity compared to unalloyed Zn samples,thus confirming their bet-ter cytocompatibility.This work demonstrates the great potential to design and modulate biodegradable Zn alloys to fulfill clinical needs by using AM technology.     

Effect of minor content of Gd on the mechanical and degradable properties of as-cast Mg-2Zn-xGd-0.5Zr alloys

RE-containing Mg alloys used as biodegradable medical implants exhibit good promising application due to their good mechanical properties and degradation resistance. In this work, effect of Gd on the microstructure, mechanical properties and biodegradation of as-cast Mg-2Zn-xGd-0.5Zr alloys was investigated. The results showed that there were mainly α-Mg, I-phase, W-phase and MgZn2 phase in Mg-Zn-Gd-Zr alloys. With increase of the Gd content, the strength of the alloys was enhanced due to the second phase strengthening and grain refinement. The degradation resistance of Mg-2Zn-0.5Zr alloy was increased by adding 0.5%–1% Gd due to the uniformly distributed second phases which acted as a barrier to prevent the pitting corrosion. However, increasing Gd content to 2% reduced the degradation resistance of the alloy due to the galvanic corrosion between the matrix and the second phases.The good degradation resistance and mechanical properties of as-cast Mg-2Zn-1Gd-0.5Zr alloy makes it outstanding for biomaterial application.