析出相对锆基非晶复合材料组织和力学性能的影响

利用铜模吸铸法制备(Zr0.72Cu0.28)100-xAlx(x=0,2,4,6,8,10,12和14)合金棒状试样,研究了合金的非晶形成能力和析出相与力学性能之间的关系。结果表明,随着Al含量增加,非晶形成能力提高;析出相体积分数和尺寸减小,分布更加均匀;综合力学性能逐渐提高,x=12时抗压强度和塑性应变均达到最高值,分别为1 773MPa和7.45%。     

非晶复合材料制备与性能

总结了近年来本课题组在外加强化相非晶复合材料制备方面取得的主要研究结果。通过制备过程凝固控制获得了性能优异的非晶复合材料,其中金属W/Zr基非晶合金双连续相复合材料压缩强度达到3 450 MPa,压缩应变为48%;金属Ti/Mg基非晶合金双连续相复合材料压缩强度达到1 750 MPa,塑性应变为30%;8%Nb颗粒/Mg基非晶复合材料压缩强度达到900 MPa,塑性应变为12.1%;6%S iC颗粒/Zr基非晶复合材料压缩强度达到2 230 MPa,塑性应变为3%。     

Ti-Zr-Cu-Co-Sn-Si块体非晶合金的形成及生物腐蚀行为和力学性能

采用铜模铸造法制备了不含高生物毒性元素Ni和Be及贵金属元素的生物医用型Ti87-xZr7.5CuxCo2.5Sn2Si1(x=39,40,42,原子分数/%)块体非晶合金,并对其非晶形成能力、热稳定性、生物腐蚀行为及力学性能进行了研究。结果表明:该系非晶合金临界直径为2~3mm,并具有较高的热稳定性,其过冷液体温度区间为44~51K。Ti-Zr-Cu-Co-Sn-Si非晶合金在模拟人体体液环境中表现出高耐腐蚀性能,在37℃的磷酸盐缓冲溶液中发生自钝化,钝化电流密度低,且其开路电位和孔蚀电位随着Ti含量的增加而提高。该系非晶合金具有良好的力学性能,压缩断裂强度达2309MPa,弹性模量为92~100GPa。     

Ta添加对(Fe_(0.46)Co_(0.36)Ni_(0.04)Zr_(0.14))_(100-x)Ta_x非晶合金复合材料磁性能和力学性能的影响

利用铜模吸铸法制备出直径为3 mm的(Fe0.46Co0.36Ni0.04Zr0.14)100-xTax(x=0,4,8,12)非晶合金复合材料柱状试样,通过X射线衍射(XRD)、选区电子衍射(SAED)、振动样品磁强计(VSM)、微机控制电子式万能力学试验机和扫描电镜(SEM)研究了不同Ta含量对合金的磁性能和压缩力学性能的影响。结果表明,随着Ta含量的增加,合金中不断有晶体相Co2Zr、Co2Ta0.5Zr0.5析出,合金的矫顽力Hc呈现出减小的趋势,而合金的饱和磁化强度Ms、抗压强度σbc和弹性应变εe则呈现出先增加后减小的趋势。当x=4时,合金的Ms、σbc和εe均达到最大值,分别为137.70A·m2/kg、1 814 MPa和4.583%。说明选取合适的Ta含量能够明显改善(Fe0.46Co0.36Ni0.04Zr0.14)100-xTax非晶合金复合材料的磁性能和力学性能。     

纤维体积分数对W纤维/Zr基非晶合金复合材料压缩性能的影响

采用渗流铸造法制备了含不同体积分数W纤维的W_f/Zr基非晶合金复合材料,其中W_f体积分数分别为47%、66%、77%和86%。研究了W_f体积分数对Zr基非晶复合材料室温准静态压缩力学性能以及变形行为的影响。结果表明:随W_f体积分数的增加,W_f/Zr基非晶复合材料的屈服强度单调增大,塑性应变先增大后减小,W_f体积分数为66%时塑性应变最大,W_f/Zr基非晶复合材料塑性应变的变化主要取决于非晶基体和W_f相互作用的程度。随着应变量的增大,基体中剪切带的数量和密度也随之增大,主剪切带向大于45°方向偏转。由于压头的影响,W_f/Zr基非晶复合材料压缩过程中样品端部和中部的受力状态不同,导致两部分的剪切带方向也明显不同。随W_f体积分数的增大,W_f/Zr基非晶复合材料的断裂方式由剪切断裂向纵向劈裂转变,断裂行为符合摩尔库伦准则。     

高温快速处理对铜基非晶合金压缩性能的影响

采用铜模吸铸法制备Cu50Zr42Al8非晶合金,并对其进行高温快速处理,通过X射线衍射(XRD)、差示扫描量热法(DSC)、场发射扫描电镜(SEM)、微机控制电子式万能力学试验机研究高温处理对Cu基非晶合金结构和压缩性能的影响。结果表明,873 K处理后的试样未析出晶体相,其它试样析出相均含有Cu10Zr7和AlCu2Zr,熔点以上处理后的试样还析出了CuZr2,且随着处理温度的升高析出相的体积分数逐渐增大;铸态试样塑性和强度最好,且随着处理温度的升高断裂强度先减小后增大,1 148 K处理的试样断裂强度最低,1 223 K处理的试样断裂强度是处理后试样中最高的,且经1 198 K处理的试样是处理后的试样中唯一出现塑性的,塑性应变为0.83%。     

ZrCuNiAlEr块体金属玻璃尺度效应的研究

通过磁悬浮熔炼-铜模吸铸法制备了直径为2,4,6 mm的(Zr_(63.36/100)Cu_(14.25/100)Ni_(10.12/100)Al_(12/100))_(100-x)Er_x(x=0.5,1,1.5,2,2.5,3)块体金属玻璃棒状试样,研究了尺寸大小对合金力学性能的影响。结果表明,当x=2,2.5时,直径为2 mm的合金试样出现了大的压缩塑性变形,塑性变形量分别达到24.59%和24.93%。而?4和6mm合金试样的压缩塑性变形基本上无变化,这就说明该非晶合金的塑性随着尺寸的增大而下降,即非晶合金压缩塑性存在尺寸效应。弹性模量、屈服强度和断裂强度也随着合金尺寸的增加而下降,即随着非晶合金尺寸的增加其力学性能逐渐降低。     

C含量对增材制造(FeCoCrNi)88-xMo8WNb3Cx高熵合金成型件组织与性能的影响

采用机械合金化方法与增材制造技术制备了(FeCoCrNi)_88-xMo₈WNb₃C_x(x=0.25、0.5、0.75、1、1.5、2、2.5)高熵合金成型件。在明确该高熵合金形成规律的基础上,进一步分析了C含量对其组织和力学性能的影响规律。结果表明：当C含量介于0.25%～2.50%(摩尔分数)之间时,(FeCoCrNi)_88-xMo₈WNb₃C_x高熵合金均由FCC相和M₆C相组成;随着C含量的增加,合金的抗压强度逐渐增加,塑性呈先增大后减小趋势;当C含量为2.00%时,合金的综合力学性能最优,其抗压强度为1 993.4 MPa,断裂应变为31.5%。     

Y添加Ti_(40)Zr_(25)Cu_9Ni_8Be_(18)非晶合金的纳米晶化及力学性能

利用铜模铸造法制备直径为3mm的(Ti_(40)Zr_(25)Cu_9Ni_8Be_(18))100-xYx(x=0,1.0,1.5,2.0,3.0)合金棒材,采用X射线衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)、差式扫描量热计(DSC)和单轴压缩测试设备对合金的组织、玻璃形成能力和力学性能进行研究。结果表明:Y元素含量为1.0%(原子分数,下同)时,合金的衍射结果为非晶态;Y元素含量为1.5%时,诱发了非晶合金的纳米晶化。在高分辨透射电镜下可观察到,非晶基体上析出5~20nm左右的晶化相,含Y为1.5%的合金抗压强度高达1990MPa,塑性应变高达3.0%;Y添加后合金断口处剪切带数量增加。多剪切带之间的交错,阻碍不均匀形变,提高了合金的塑性和强度。     

添加Nd对Mg-Zn-Ca合金非晶形成能力和耐蚀性的影响

采用真空铜模喷铸法制备了直径为2 mm的Mg68-xZn28Ca4Ndx(x=0,0.5,1,1.5)合金,研究了Nd添加量对合金的非晶形成能力以及耐腐蚀性能的影响。利用SEM、EDS能谱分析了模拟体液中浸泡不同时间后非晶合金的显微组织与成分,利用XRD和DSC分析了合金的相组成和非晶形成能力,利用电化学工作站对合金在模拟体液中的电化学性能进行了测试。结果表明,随着Nd添加量的增加,合金的非晶形成能力下降,当Nd元素的添加量为1.0%和1.5%时,α-Mg相在非晶基体上析出,试样由纯非晶结构转变为晶体和非晶的复合结构。Mg67.5Zn28Ca4Nd0.5非晶试样展现了最好的抗腐蚀性能。     

微量Al添加对铜基大块非晶合金性能的影响

为了进一步提高铜基大块非晶合金的玻璃形成能力及力学性能,采用添加微量Al元素的方法对块体非晶合金Cu52.5Ti30Zr11.5Ni6进行了成分优化.热分析与X射线衍射结果显示,随着微量Al的添加,液相线温度从非晶合金Cu52.5Ti30Zr11.5Ni6的1150 K逐步降低到Cu50.5Ti30Zr11.5Ni6Al2的1134 K,临界直径相应的从5 mm提高到6 mm.大块非晶Cu50.5Ti30Zr11.5Ni6Al2的压缩断裂强度达到2286 MPa,比经典的铜基非晶合金Cu47Ti34Zr11Ni8提高约100 MPa,表明微量Al的添加在有效提高玻璃形成能力的同时,强度也略有提高.     

Novel β-type Zr–Mo–Ti alloys for biological hard tissue replacements

In order to develop new biomaterials for hard tissue replacements, Zr–12Mo–xTi (x = 0, 3, 7 and 11, in at.%) alloys with required properties have been designed and prepared using vacuum arc melting method for the first time. Phase analysis and microstructural observation shows that all the as-cast samples consist of equiaxed β-Zr phase. Variations of lattice constants, volume and density of the Zr–12Mo–xTi alloys as a function of Ti content have been discussed. With the increase of Ti content, the microstructure is refined. The solid solution effect of the β-phase stabilization elements (i.e. Mo and Ti) predominantly determines the mechanical properties. These β-type Zr–12Mo–xTi alloys exhibit high compressive strength (1469–1584 MPa), high yield strength (1175–1375 MPa), high elastic energy (21–28 MJ/m³) and low Young’s modulus (32–35 GPa), together with plastic strain (11–25%). As the Zr–12Mo–xTi alloys are based on biocompatible elements, this good combination of biomechanical characteristics makes them potential biomedical materials for hard tissue replacements.     

高温处理后闭孔泡沫铝压缩性能及变形机理

目的 探究温度和孔隙率对闭孔泡沫铝材料压缩力学性能和变形机理的影响。方法 将孔隙率为84.3%～87.3%的泡沫铝试件在温度25～700 ℃内进行加热处理,对处理后的试样开展准静态压缩实验。结果 在准静态压缩条件下,闭孔泡沫铝材料在不同温度加热处理后的压缩应力–应变曲线均经历了3个阶段:弹性阶段、塑性平台阶段和密实阶段。孔隙率从87.3%减小到84.3%时,其弹性模量增大了44.4 MPa,屈服强度增大了0.39 MPa,平台应力增大了0.94 MPa。孔隙率为84.3%的泡沫铝,在25 ℃时,其弹性模量为141.4 MPa、屈服强度为4.25 MPa、平台应力为4.75 MPa;当加热温度为500 ℃时,弹性模量减小到了128.0 MPa、屈服强度减小到了4.22 MPa、平台应力减小到了4.51 MPa。结论 泡沫铝的弹性模量、抗压屈服强度和平台应力均随孔隙率的增加而减小;加热温度低于500 ℃以下时,泡沫铝材料力学性能变化很小,但屈服强度和弹性模量均小幅度降低;在压缩载荷下,泡沫铝的变形破坏模式呈现出先从试件铝基体较薄弱部分产生孔壁塑性变形、孔洞坍塌,并逐渐出现断裂压缩带,直至泡沫铝孔洞完全坍塌密实。     

Effect on microstructure and plastic deformation behavior of a Zr-based amorphous alloy by cooling rate control

In this study,Zr41.2Ti13.8Cu12.5Ni10Be22.5 amorphous alloys samples with the same diameter(8 mm)were prepared by using self-designed molds(viz.refractory steel,pure graphite,and copper molds)with dif-ferent cooling capacities.Moreover,by eliminating the size effect,the effect of the cooling rate on the microstructure and compression deformation behavior of Zr41.2Ti13.8Cu12.5Ni10Be22.5 amorphous alloys was investigated.Differentiation of the cooling curves revealed that the instantaneous cooling rates of the alloy melt at the glass transition temperature(Tg)are 45,52,and 64K·s-1 for refractory steel,pure graphite,and copper molds,respectively.X-ray diffraction,differential scanning calorimetry,and high-resolution transmission electron microscopy analysis revealed that with the decrease in the cooling rate,trace icosahedral-like atomic clusters and nanocrystals appear in local areas of the amorphous alloy and that the amount of free volume decreases with the increase in the amount of icosahedra-like atomic clusters and nanocrystals.Compression test results revealed that the elastic strain,yield strength,and compressive strength of the amorphous alloy marginally change with the decrease in the cooling rate,while the plastic strain gradually increases.By fitting,the effective size of the vein-like pattern was lin-early related to the enthalpy released during structural relaxation and plastic strain,indicating that at a low cooling rate,the trace nanocrystals in the amorphous alloy could not effectively improve its plasticity and that the amount of free volume mainly affects its plasticity.     

Fe_(88-x)Zr_xB_(12)合金的结构及晶化研究

采用机械合金化法制备Fe88-xZrxB12(X=5、10、15、20)系合金,利用X射线衍射仪(XRD)、差热分析仪(DTA)等测试手段对样品的结构及晶化进行研究.XRD结果表明,球磨60h,Fe88-xZrxB12(x=5、10、15)已形成α-Fe固溶体,Fe68Zr20B12完全形成非晶合金,表明Zr含量的增加使合金的非晶形成能力增强.Fe88-xZrxB12(x=5、10、15、20)合金的DTA图中均出现2个晶化放热峰.Fe68Zr20B12非晶合金的晶化模式为一次晶化.     

Ti35Nb7Zr-xHA生物复合材料的微观组织与性能研究

为了改善Ti-Nb-Zr合金的生物活性,采用放电等离子烧结(SPS)技术制备了不同羟基磷灰石(HA)含量的Ti35Nb7Zr-xHA(x=0、5、10、20(质量分数,%))生物复合材料,研究了HA含量对复合材料微观组织、力学性能及体外生物活性的影响。结果表明,复合材料主要由β-Ti、α-Ti、HA及陶瓷相(Ti_xP_y、CaTiO_3、Ti_2O、CaO)组成;HA含量增加会导致β-Ti减少而α-Ti和陶瓷相明显增多;与Ti-35Nb-7Zr合金(E:45GPa,σ:1 736 MPa)相比,HA含量为5%和10%时,复合材料的抗压强度分别为1 662MPa和1 593MPa,弹性模量分别为48GPa和49GPa,综合力学性能与Ti-35Nb-7Zr合金接近,展现出良好的力学性能,而过高的HA含量(20%)会导致复合材料弹性模量明显升高(E:55GPa)、抗压强度急剧下降(σ:958 MPa),复合材料的力学性能降低;体外生物活性实验表明,加入10%HA的复合材料在人工模拟体液(SBF)中浸泡7d后表面生成了大量的类骨磷灰石层,与Ti-35Nb-7Zr合金相比,其显示出更优异的体外生物活性。     

新型Zr-Nb基大块非晶合金的形成及性能

本文用水淬法制备 Zr-Nb基大块非晶合金 ;并采用 DSC热分析法测定了该种合金的玻璃转变温度和热稳定性 ;采用超声检测方法精确测定了材料的声学性能 ,由此计算得到一组大块非晶合金的弹性性能参数。     

Effect of Er on properties of Zr-based bulk metallic glasses

(Zr_0.6336Cu_0.1452Ni_0.1012Al_0.12)_100-xEr_x(x?=?0～6) bulk metallic glasses were fabricated by copper mould suction casting method, and the effect of Er on properties was studied. The compressive plastic strain (ε_p) and compressive strength (σ_max) at room temperature increases first and then decreases with the increase of Er content. The compressive plastic strain (ε_p) of the specimen is 35.1% when x?=?2.6, which is about eight times than that of the specimen with x?=?0. The compressive strength (σ_max) is 2513?MPa, which is much higher than that of the specimen with x?=?0. It indicates that Zr-based bulk metallic glasses could be strengthened and toughened by adding Er. The thermal stability decreases gradually and the glass-forming ability increases first and then decreases with the increase of Er content.     

Superior mechanical properties and strengthening mechanisms of lightweight AlxCrNbVMo refractory high-entropy alloys(x = 0, 0.5,1.0) fabricated by the powder metallurgy process

Light and strong AlxCrNbVMo(x=0,0.5,and 1.0) refractory high-entropy alloys(RHEAs) were designed and fabricated via a the powder metallurgical process.The microstructure of the AlxCrNbVMo alloys consisted of a single BCC crystalline structure with a sub-micron grain size of 2-3 μm,and small amounts(4 vol.%) of fine oxide dispersoids.This homogeneous microstructure,without chemical segregation or micropores was achieved via high-energy ball milling and spark-plasma sintering.The alloys exhibited superior mechanical properties at 25 and 1000℃ compared to those of other RHEAs.Here,CrNbVMo alloy showed a yield strength of 2743 MPa at room temperature.Surprisingly,the yield strength of the CrNbVMo alloy at 1000℃ was 1513 MPa.The specific yield strength of the CrNbVMo alloy was increased by 27 % and 87 % at 25 and 1000℃,respectively,compared to the AlMo_(0.5) NbTa_(0.5)TiZr RHEA,which exhibited so far the highest specific yield strength among the cast RHEAs.The addition of Al to CrNbVMo alloy was advantageous in reducing its reduce density to below 8.0 g/cm~3,while the elastic modulus decreased due to the much lower elastic modulus of Al compared to that of the CrNbVMo alloy.Quantitative analysis of the strengthening contributions,showed that the solid solution strengthening,arising from a large misfit effect due to the size and modulus,and the high shear modulus of matrix,was revealed to predominant strengthening mechanism,accounting for over 50 % of the yield strength of the AlxCrNbVMo RHEAs.     

ZK60和ZK60-1.0Er镁合金热压缩变形和加工图

采用Gleeble-1500D热模拟试验机对ZK60和ZK60-1.0Er镁合金进行了热压缩实验,分析了合金在温度为160~420℃,应变速率为0.0001~1.0s-1条件下的流变应力变化特征。结果表明:两种镁合金在热压缩过程中的流变应力随变形温度的降低和应变速率的升高而增加,在流变应力达到峰值后随即进入稳态流变;稀土Er的加入使得平均变形激活能珚Q值由183kJ/mol降到153kJ/mol,应力指数n值由6提高到8;发生动态再结晶的临界应力σc值随变形温度升高和应变速率降低而降低,在420℃/1.0s-1高温高应变速率时,稀土Er的加入使得ZK60镁合金发生动态再结晶的临界应力值σc由76MPa降到50MPa。通过动态模型构建热加工图并结合金相组织观察可知:稀土Er的加入缩小了ZK60镁合金的热加工失稳区,增加了热加工安全区的功率耗散效率峰值η_(max),由35%增大到45%,促进了动态再结晶晶粒的形核,但抑制了再结晶晶粒的长大。