FeCoNiMnB_x高熵合金微观组织及力学性能的研究

采用真空电弧熔炼技术熔炼了FeCoNiMnB_x(x=0,0.0 5,0.1,0.15,0.20)高熵合金,然后对合金的微观组织及其力学性能进行测试。结果表明,未加入B元素时,合金组织具有单一FCC结构。当B含量≥0.05at%时,组织由基体FCC相+B_2Co_3组成;当B含量从0.05at%增加到0.20at%时,该合金的硬度逐渐增加,B含量为0.20at%时,该合金的硬度达到最大,为274 HV。     

Nb含量对Fe0.5MnNi1.5CrNb x 高熵合金微观结构和力学性能的影响

采用真空感应熔炼法制备了Fe_0.5MnNi_1.5CrNb_x（x=0,0.05,0.1,摩尔比）高熵合金,并分析了不同Nb含量对其组织和力学性能的影响。结果表明,不含Nb元素的合金具有单相fcc结构,其抗拉强度和断裂延伸率（即延展性）分别为519 MPa和47%。添加少量的Nb(x=0.05)后出现(200)织构和少量Fe₂Nb Laves相,合金的延展性增加到55%,并且抗拉强度增加到570 MPa。当Nb含量增加到x=0.1时,织构减少,而Fe₂Nb Laves相增多,抗拉强度和延展性分别为650 MPa和45%。     

AlxFeCoNiB0.1高熵合金的微观组织和力学性能研究

采用真空电弧炉熔炼制备了AlxFeCoNiB0.1（x=0.4,0.5,0.8,1.2,1.6 at%）高熵合金,并对其微观组织和力学性能进行测试。随Al含量增加,合金的铸态枝晶由FCC相转变为B2(AlNi)/BCC相。当x=0.4和0.5时,合金的组织由枝晶FCC相和枝晶间组织B2相及(Fe,Co)2B组成;x=0.8时,枝晶由B2相组成,枝晶间由FCC相及(Fe,Co)2B组成;x=1.2时,枝晶间由共晶组织FCC+(Fe,Co)2B组成,BCC呈纳米级颗粒状;x=1.6时,共晶组织消失。随Al含量的增加,抗压拉强度先上升后下降,Al含量为0.8时达到峰值,为2243MPa,适量的Al能提高高熵合金综合力学性能。     

AlCrCuFeNbxNiTi高熵合金组织与性能研究

采用电弧熔炼制备了AlCrCuFeNb_xNiTi (x = 0, 0.25, 0.5, 1.0)高熵合金,研究不同Nb含量对AlCrCuFeNb_xNiTi高熵合金显微组织和力学性能的影响。研究表明：AlCrCuFeNb_xNiTi (x = 0, 0.25, 0.5, 1.0)高熵合金物相主要包含有序FCC的L2₁相和Laves相,还有少量的BCC(A2)和FCC相;Nb元素的添加能促进Laves相的生成且对Cu元素的偏析具有一定的抑制效果;通过相判据参数计算找到了适合AlCrCuFeNb_xNiTi高熵合金的相形成判据;添加适量的Nb元素能够改善AlCrCuFeNiTi六元高熵合金的力学性能;AlCrCuFeNb_0.5NiTi 高熵合金具有较好的综合力学性能,抗压强度达到1587.4 MPa,硬度达到568.8 HV;Nb元素含量过高时会形成过多的Laves相使合金表现出过早脆化现象。     

放电等离子烧结制备低密度AlTiCrNiCu高熵合金及其组织性能研究

采用机械合金化和放电等离子烧结工艺制备了低密度AlTiCrNiCu高熵合金材料,重点研究了球磨时间对各元素粉末的合金化过程及烧结温度(950 ~ 1050 ℃)对高熵合金组织及力学性能的影响。结果表明：高熵合金粉末为单相BCC结构,随着球磨时间的增加,粉末粒径先变大后变小,其最终平均粒径大约为20 μm。高熵合金块体材料的相结构为BCC1(基体相)+BCC2(富Cr相)+FCC(富Cu相),密度为6.22 ~ 6.30 g/cm_³。烧结温度的升高,有利于高熵合金粉末的冶金结合,促进了高熵合金块材料的致密化。当烧结温度为1050 ℃时,AlTiCrNiCu高熵合金具有良好的综合力学性能,其屈服强度、压缩强度、塑性和显微硬度分别为1410 MPa,2000 MPa,9.13%和524 HV。分析认为高的烧结温度为各元素原子间的充分扩散提供了足够的能量。然而,TEM分析表明,高的烧结温度也促进了弥散的FCC富Cu相在晶界的聚集长大。     

超细晶粉末冶金CoCrFeMnNiGd0.15高熵合金的组织性能

采用机械合金化和放电等离子烧结的方法制备出超细晶CoCrFeMnNiGd_0.15合金,研究了CoCrFeMnNiGd_0.15高熵合金的组织与性能。结果表明,其组织为多相结构,基体为FCC固溶体相,析出相为稀土氧化物(Gd₂O₃)和富Gd、Ni、Mn的四方结构相。随着烧结温度的提高,析出相的含量不断增加且尺寸不断增大,合金的压缩屈服强度不断下降而塑性则不断上升。在900℃烧结时材料具有最优的综合力学性能,其压缩屈服强度(σ_0.2)、抗压强度(σ_max)、断裂时的塑性应变(ε_p)和维氏硬度分别达到1662 MPa、2518 MPa、30.6%和458 Hv。     

铸态Mg-Li-Al-xSi合金微观组织和力学性能

本文通过真空熔炼炉在氩气保护下制备了Mg-9Li-3Al-xSi(x=0,0.1,0.5,1.0 wt%)合金。实验使用光学显微镜(OM),扫描电子显微镜(SEM),力学性能测试和X射线衍射(XRD)研究合金的微观组织和力学性能。实验结果表明：铸态Mg-9Li-3Al合金组织中主要由α-Mg、β-Li、Mg₁₇Al₁₂相组成。加入Si后,合金中出现了新相Mg₂Si,晶粒得到了明显细化;当合金中的Si含量过高时,α-Mg相粗化,且会在相界处出现块状和汉字状的Mg₂Si相。合金的强度随着Si含量的增加呈现先增加后降低的趋势,合金的延伸率随着Si含量的增加呈现逐渐降低的趋势。当合金中Si含量为0.1%时,抗拉强度达到最大值182.5MPa,延伸率为12.1%,相比未添加Si的Mg-9Li-3Al合金,抗拉强度提高了59.6%。     

Nb含量对Fe_(0.5)MnNi_(1.5)CrNb_x高熵合金微观结构和力学性能的影响（英文）

采用真空感应熔炼法制备了Fe_(0.5)MnNi_(1.5)CrNb_x(x=0,0.05,0.1,摩尔比)高熵合金,并分析了不同Nb含量对其组织和力学性能的影响。结果表明,不含Nb元素的合金具有单相fcc结构,其抗拉强度和断裂延伸率(即延展性)分别为519 MPa和47%。添加少量的Nb(x=0.05)后出现(200)织构和少量Fe_2Nb Laves相,合金的延展性增加到55%,并且抗拉强度增加到570 MPa。当Nb含量增加到x=0.1时,织构减少,而Fe_2Nb Laves相增多,抗拉强度和延展性分别为650 MPa和45%。     

铸态Fe_x(CoCrNiV)_(100-x)合金的组织与性能

利用真空电弧炉熔炼并制备了Fe_x(CoCrNiV)_(100-x)高熵合金。采用金相显微镜、X射线衍射仪、扫描电镜、能谱仪和万能拉伸试验机等手段测试和分析了不同Fe含量下Fe_x(CoCrNiV)_(100-x)高熵合金的组织与力学性能。结果表明,Fe_x(CoCrNiV)_(100-x)高熵合金的金相组织为典型的树枝晶或片层组织;随Fe含量的增加,合金的相结构由FCC+金属间化合物(σ相)先转变为FCC+BCC+σ相,再转变为FCC+BCC相,最后转变为BCC单相;x=50合金的强韧性综合性能最好,抗拉强度达到857.3 MPa,总伸长率达到39.4%。     

Zn添加对Mg-8Al-2Sn镁合金组织和性能的影响

本文以Mg-8Al-2Sn变形镁合金为研究背景,通过在Mg-8Al-2Sn合金中添加0-2 wt.%含量的Zn元素,研究了Zn添加对Mg-8Al-2Sn挤压镁合金显微组织和性能的影响。研究结果表明,铸态Mg-8Al-2Sn-xZn合金的相组成主要是α-Mg相、Mg₁₇Al₁₂相和Mg₂Sn相。在添加Zn元素以后,合金中的共晶化合物的形态发生变化,由共晶组织变为离异共晶组织。挤压过后,晶粒组织尺寸更均匀。Zn元素的加入,会促进合金中第二相在挤压过程中的动态析出以及第二相尺寸的粗化。合金在时效中产生的析出相的数量也随着Zn含量的增多而增加。随着Zn含量的增加,挤压态和时效态合金的屈服强度和抗拉强度都随之增加。当Zn含量达到2 wt.%时,合金力学性能最好,其时效态的抗拉强度,屈服强度和延伸率分别是385 MPa, 291 MPa和6.44%。     

Effects of Chromium on the Microstructures and Mechanical Properties of AlCoCrxFeNi2.1 Eutectic High Entropy Alloys

In the present study,a series of AlCoCrxFeNi2.1 (x=0,0.25,0.5,0.75,1.0) eutectic high entropy alloys (EHEAs) have been designed and prepared.And the effect of Cr content on the microstructures and mechanical properties of the AlCoCrxFeNi2.1 alloys was systematically investigated.The results indicate that the AlCoCrxFeNi2.1 (x ＞ 0) alloys exhibit almost complete lamellar eutectic microstructures with a mixture structure of FCC and B2 phases.And the AlCoFeNi2.1 alloy without Cr element exhibited a hypoeutectic microstructure with a primary B2 phase.In addition,the eutectic microstructures for AlCoCrxFeNi2.1 eutectic alloys do not change significantly.The room temperature compressive tests results show that with an increase in Cr content (from x =0 to x =1.0),the yield strength will first decrease,and thereafter increase.The trend is the opposite with the fracture strength and plastic strain.They show an increase trend at first,and then decrease.The AlCoCr0.5FeNi2.1 (Cr0.5) alloy shows the best comprehensive mechanical properties.The tensile yield strength,fracture strength,and elongation are 536.5 MPa,1062 MPa,and 13.8％,respectively.Furthermore,the Cr0.5 alloy also displays a high strength with a yield strength of 362 MPa at 700 ℃.In summary,by changing the Cr content,AlCoCrxFeNi2.1 eutectic high entropy alloys with excellent comprehensive mechanical properties were obtained and prepared.     

Mg-Zn-Y-Nd-Zr合金的显微组织、织构、力学性能

对Mg-Zn-Y-Nd-Zr合金的显微组织和力学性能进行了研究。结果表明,Nd元素的加入部分取代了W相（Mg₃Zn₃Y₂）中的Y元素,形成了新的第二相Mg₃Zn₃(Y, Nd)₂。热挤压后观察到由细小的等轴再结晶晶粒和粗大的细长未再结晶晶粒组成的典型双峰结构。Nd元素的加入促进了热挤压过程中的动态再结晶,随着Nd含量的增加,动态再结晶率增加,挤压态合金的整体织构强度减弱。Nd的加入细化了晶粒并改善了合金的力学性能。添加0.5%（质量分数）Nd时,挤压态合金表现出高强度和高塑性的良好结合：屈服强度为362 MPa,极限抗拉伸强度为404 MPa,延伸率为10.2%。时效处理后合金的抗拉伸强度进一步提高,峰值时效极限抗拉伸强度可达421 MPa。合金的高强度主要归功于超细再结晶晶粒和析出强化。     

Mg-Bi合金的显微组织和力学性能

采用挤压铸造和挤压变形工艺制备了Mg-Bi二元合金,通过金相显微镜分析,室温拉伸性能测试,X射线衍射分析,SEM和EDS等手段,研究了Mg-Bi合金在铸态和热挤压态的显微组织和力学性能.结果表明:铸态Mg-Bi合金随着Bi含量的增加,伸长率逐渐降低,抗拉强度逐渐增加,当Bi含量达10wt.％以上,抗拉强度降低;Mg-Bi合金铸锭经450℃、3h保温,挤压比为12.76热挤压后,随Bi含量的增加,抗拉强度与伸长率均逐渐增加,当Bi含量达12wt.％时,抗拉强度为219.68 MPa,伸长率为13.43％,Bi含量继续增加,合金抗拉强度及伸长率呈下降趋势;挤压态Mg-Bi合金的力学性能是晶粒细化与Mg3Bi2综合作用的结果,当Bi含量大于12wt.％后,形成较多粗大的Mg3Bi2相是导致合金力学性能下降的主要原因.     

Mechanical properties,corrosion behavior,and microstructure of Sr modified Al–9.2Mg–0.7Mn alloys

The influence of strontium (Sr) additions in the form of Mg–Sr master alloys from 0 to 0.6 wt% on the mechanical properties, corrosive nature, and microstructure of Al–9.2Mg–0.7Mn alloys is investigated. The material is studied in a fully annealed (O‐temper) and a sensitizing treatment at 150°C for 7 days. Here we demonstrate that there will be a new phase which might be (Al, Mg)₁₇Sr₂ formed in the as‐cast microstructure. When the Sr content is 0.2 wt%, under the premise that the mechanical properties of completely annealed alloy change little (relative to the matrix: the ultimate tensile strength increases by 8 MPa and the elongation only decrease by 1.6%), the intergranular corrosion resistance is significantly improved. The specific performance is that the mass loss from intergranular corrosion decreases by more than 53% from the addition of 0.2 wt% Sr after sensitizing.     

Gd添加量对Zn-1.2Cu-1.2Mg锌合金组织和性能的影响

研究了Zn-1.2Cu-1.2Mg-xGd（x=0,0.1,0.25,0.5,质量分数,%）锌合金微观组织、在模拟体液中的腐蚀行为和力学性能。结果表明,锌合金组织主要由Zn固溶体和Mg₂Zn₁₁金属间化合物组成。当Gd添加量为0.5%时,形成了GdZn₁₂化合物。锌合金的硬度随Gd添加量的增加而增加,在0.5% Gd添加量时,硬度达到最大值为1530 MPa。在0.25% Gd添加量时锌合金具有高的抗拉伸强度,而在0.1% Gd添加量时锌合金具有最低的腐蚀速率。     

Microstructure,anticorrosion, biocompatibility and antibacterial activities of extruded Mg−Zn−Mn strengthened with Ca

To find suitable biodegradable materials for implant applications, Mg?6Zn?0.3Mn?xCa (x=0, 0.2 and 0.5, wt.%) alloys were prepared by semi-continuous casting followed by hot-extrusion technique. The microstructure and mechanical properties of Mg?6Zn?0.3Mn?xCa alloys were investigated using the optical microscope, scanning electron microscope and tensile testing. Results indicated that minor Ca addition can slightly refine grains of the extruded Mg?6Zn?0.3Mn alloy and improve its strength. When 0.2 wt.% and 0.5 wt.% Ca were added, the grain sizes of the as-extruded alloys were refined from 4.8 to 4.6 and 4.2 μm, respectively. Of the three alloys studied, the alloy with 0.5 wt.% Ca exhibits better combined mechanical properties with the ultimate tensile strength and elongation of 334 MPa and 20.3%. The corrosion behaviour, cell viability and antibacterial activities of alloys studied were also evaluated. Increasing Ca content deteriorates the corrosion resistance of alloys due to the increase of amount of effective cathodic sites caused by the formation of more Ca₂Mg₆Zn₃ phases. Cytotoxicity evaluation with L929 cells shows higher cell viability of the Mg?6Zn?0.3Mn?0.5Ca alloy compared to Mg?6Zn?0.3Mn and Mg?6Zn?0.3Mn? 0.2Ca alloys. The antibacterial activity against Staphylococcus aureus is enhanced with increasing the Ca content due to its physicochemical and biological performance in bone repairing process.     

Enhancement of mechanical properties of duplex Mg-9Li-3Al alloy by Sn and Y addition

For enhancement of mechanical properties in Mg-9Li-3Al alloys, Mg-9Li-3Al duplex alloys were alloyed by addition of Sn and Y. Microstructure evolution and mechanical property response of as-cast Mg-9Li-3Al alloys by alloying with Sn and Y were investigated by optical microscopy, scanning electron microscopy, X-ray diffractometry and tensile tests. The results indicate that considerable blocky dendrites of primary α phase in Mg-9Li-3Al alloys become lath-like due to the addition of Sn. With addition of Y, Mg-9Li-3Al alloy consists of both block-like and lath-like α-Mg dendrites. The as-cast Mg-9Li-3Al-1Sn-1Y alloy shows a yield strength of 118 MPa, ultimate tensile strength of 148 MPa and the elongation to failure of 21%. Improvement in both strength and elongation of Mg-9Li-3Al alloys with Sn and Y addition is attributed to the combined action of MgLi₂Sn and Al₂Y intermetallic compounds.     

流变挤压铸造制备LPSO结构增强Mg-Zn-Y-Zr合金及其组织性能

采用流变挤压铸造工艺制备了含有LPSO结构的Mg99.9-3xZnxY2xZr0.1(x=0.5、1、2,摩尔分数,%)合金,研究了合金的微观组织特征及力学性能。结果表明,流变挤压铸造能有效细化合金的微观组织。合金的基体组织由尺寸较大的α1-Mg和尺寸较小的α2-Mg晶粒组成,LPSO结构呈细小的网状结构均匀地分布在晶界处,LPSO结构的含量越低,其细化效果越明显。随着挤压压力增大,合金中LPSO结构的厚度越来越小,当压力达到100MPa后,厚度变化趋缓。与常规重力铸造相比,流变挤压铸造能有效提高合金的力学性能,特别是伸长率。在400MPa下的流变挤压铸造Mg96.9Zn1Y2Zr0.1合金的抗拉强度和伸长率较重力铸造下分别提高了19%和170%。     

Al_(0.25)Cu_(0.75)FeNiCo颗粒增强铝合金的组织与性能

高熵合金是一种新型的结构与功能材料,源于金属-金属间天然的界面结合特性,高熵合金与铝合金基体间的界面润湿性极好。采用Al_(0.25)Cu_(0.75)FeNiCo高熵合金(HEA)颗粒作为增强相来增强铝合金,研究高熵合金含量变化对复合材料显微组织和力学性能的影响。结果表明:高熵合金增强相在基体中分布均匀,随着高熵合金体积分数的增大,局部会出现少量颗粒团聚现象。复合材料的弹性模量和硬度随着高熵合金含量的增加而增大,但复合材料的抗拉强度和延伸率呈现出先增大后减小的趋势。当高熵合金的体积分数为5%时,复合材料的极限抗拉强度和伸长率达到最大值(σb:437.6 MPa,ε:11.42%),比铝合金基体分别提高了20.1%和36.6%。TEM分析表明,高熵合金颗粒和铝合金良好的界面结合状态,使得复合材料具有较高的综合力学性能。