退火温度对等通道转角挤压态铁基形状记忆合金力学性能的影响

研究了退火温度对等通道转角挤压(ECAP)Fe17.80Mn4.73Si7.80Cr4.12N i合金力学性能及显微组织的影响。结果表明,等通道挤压工艺能显著提高合金的屈服强度和抗拉强度,两道次挤压后合金的屈服强度达到880 MPa,比固溶态高660 MPa。退火温度从300℃升高到600℃时,合金屈服强度和抗拉强度降低,伸长率升高。挤压后经700℃×30 m in退火后,材料的伸长率达到40%,屈服强度达到426 MPa,再结晶基本完成,晶粒尺寸仅为0.3~2.5μm。细晶强化是该合金强度和伸长率提高的主要原因。     

机械合金化联合真空热压烧结工艺制备CoCrFeNi高熵合金的力学性能和耐腐蚀性能

采用机械合金化和真空热压烧结工艺制备了CoCrFeNi高熵合金。采用X射线衍射仪、扫描电子显微镜、电感耦合等离子体发射光谱和光学显微镜对产物的相结构和微观结构进行了表征,并采用万能试验机、维氏硬度计和电化学工作站对其力学性能和耐腐蚀性能进行了研究。结果表明：与电化学还原联合热压烧结工艺以及电弧熔炼法制备的CoCrFeNi高熵合金性能相比,机械合金化联合真空热压烧结工艺制备的CoCrFeNi高熵合金具有良好的抗拉伸强度和断裂伸长率,其合金硬度是电弧熔炼法制备合金的2倍,在0.5 mol/L H₂SO₄、1 mol/L KOH和3.5%（质量分数）NaCl水溶液中,该合金具有与304不锈钢及电化学还原联合热压烧结工艺或电弧熔炼法制备的合金相当的耐腐蚀性能。     

Effect of Argon-Induced Porosity on Mechanical Properties of Powder Metallurgy Titanium Alloy Components using Hot Isostatic Pressing

This work reported the Ar-induced porosity in powder metallurgy Ti-5Al-2.5Sn alloy prepared by hot isostatic pressing(HIPing).The obtained microstructures of powder compacts were studied through optical and scanning electron micro-scopes,X-ray tomography,and the mechanical properties evaluated through tensile and impact tests.The results showed that the Ar-induced porosity is related to the hollow powder with gas bubble and the Ar leakage of sealed container during the powder densification.The hollow powder with gas bubble shows no obvious effects on mechanical properties of as-HIPed powder compacts.The Ar content decreases with the increasing shrinkage of encapsulated powder.0.7％ Ar-induced porosity degrades the impact toughness,but no reductions of tensile properties were obtained.Ar content test is an effective method to detect the powder compacts with Ar concentration.     

TC4钛合金与Al6061铝合金热等静压扩散连接接头的界面特征及力学性能

对TC4钛合金和Al6061铝合金的异种金属进行了热等静压扩散连接实验,研究了TC4/Al6061连接接头的界面特征、形成机制和力学性能,并通过热力学分析解释相关实验现象。结果表明,热等静压扩散连接及后续退火处理后,两侧母材元素发生了明显的互扩散,其中Si、Mg元素在化学势驱动力作用下分别富集于扩散过渡区和Al侧界面。接头界面发生冶金反应生成TiAl₃、TiAl、Ti₃Al等金属间化合物,通过有效生成热模型计算表明TiAl₃相优先生成。硬度实验表明界面生成的Ti-Al金属间化合物具有较高的硬度。拉伸实验显示接头最大抗拉伸强度达到了144 MPa。     

Tensile and Fracture Properties of 15 vol% SiC_p/2009Al Composites Fabricated by Hot Isostatic Pressing and Hot Extrusion Processes

15 vol% silicon carbide particle （SiCp）-reinforced 2009A1 matrix （15 vol% SiCp/2009A1） composites were fabricated by hot isostatic pressing （HIP） and hot extrusion processes. The tensile and fracture properties of 15 vol% SiCp/ 2009Al were studied. The results showed that hot extrusion increased the ultimate tensile strength （UTS）, yield strength （YS）, elongation （EL）, reduction in area （RA）, and fracture toughness of the composites. The heat treatment resulted in the increase in UTS, YS, and fracture toughness, but a decrease in EL and RA. Both hot extrusion and heat treatment had negligible effects on elastic modulus （E）. With the increase of SiCp size, the UTS, YS, and E decreased, but the EL and RA increased. The fracture toughness increased first and then decreased with increasing SiCp size, and when the SiCp size was about 7 μm, the composites obtained the maximum fracture toughness value of 31.74 MPa m^1/2.     

Wear Properties of Porous NiTi Orthopedic Shape Memory Alloy

Porous NiTi shape memory alloy (SMA) scaffolds have great potential to be used as orthopedic implants because of their porous structure and superior physical properties. Its metallic nature provides it with better mechanical properties and Young??s modulus close to that of natural bones. Besides allowing tissue ingrowth and transfer of nutrients, porous SMA possesses unique pseudoelastic properties compatible to natural hard tissues like bones and tendons, thus expediting in vivo osseointegration. However, the nickel release from debris and the metal surface may cause osteocytic osteolysis at the interface between the artificial implants and bone tissues. Subsequent mobilization may finally lead to implant failure. In this study, the wear properties of porous NiTi with different porosities processed at different treatment temperatures are determined. The results of the study show that the porosity, phase transformation temperature, and annealing temperature are major factors influencing the wear characteristics of porous NiTi SMA.     

铝合金铸件缩松缺陷的热等静压处理

为了消除某铝合金铸件通过铸造工艺无法消除的缩松缺陷,试验了热等静压技术对此缩松缺陷消除的效果.结果表明,铸件经热等静压处理后,X射线检测缩松缺陷得到了显著改善,内部质量能达到验收标准要求.这说明热等静压技术消除该铝合金铸件缩松缺陷是可行的,也能为铝合金铸件消除缺陷提供一些参考.     

热等静压处理对选区激光熔化成形Inconel 718合金各向组织及力学性能的影响

目的 研究热等静压处理对选区激光熔化（SLM）成形不同沉积方向Inconel 718合金试样显微组织和力学性能的影响规律,提升Inconel718合金的综合力学性能。方法 采用SLM技术制备平行沉积方向和垂直沉积方向的Inconel 718合金试样,并对试样进行热等静压（HIP）处理和热等静压+固溶时效（HIP+HT）处理。利用金相显微镜（OM）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线衍射仪（XRD）和电子背散射衍射（EBSD）,对合金的显微组织、断口形貌、物相组成、晶粒形貌及取向进行分析。对试样进行显微硬度和拉伸强度性能测试,对比分析不同沉积方向SLM、HIP及HIP+HT试样的显微硬度、拉伸强度、屈服强度以及断口延伸率。结果 SLM成形的Inconel718合金经热等静处理后,平行方向的晶粒形态由柱状晶转变为等轴晶,晶粒尺寸增大,并伴随有孪晶形成。晶界处的Laves相基本溶解,同时有许多MC碳化物在γ基体中析出。不同处理状态下平行方向试样的拉伸强度、屈服强度和硬度值均小于垂直方向。平行和垂直方向SLM成形件的拉伸强度σb分别为996.3MPa和1051.1MPa...     

Tensile and Fracture Properties of 15 vol% SiCp/2009Al Composites Fabricated by Hot Isostatic Pressing and Hot Extrusion Processes

15 vol% silicon carbide particle (SiC_p)-reinforced 2009Al matrix (15 vol% SiC_p/2009Al) composites were fabricated by hot isostatic pressing (HIP) and hot extrusion processes. The tensile and fracture properties of 15 vol% SiC_p/2009Al were studied. The results showed that hot extrusion increased the ultimate tensile strength (UTS), yield strength (YS), elongation (EL), reduction in area (RA), and fracture toughness of the composites. The heat treatment resulted in the increase in UTS, YS, and fracture toughness, but a decrease in EL and RA. Both hot extrusion and heat treatment had negligible effects on elastic modulus (E). With the increase of SiC_p size, the UTS, YS, and E decreased, but the EL and RA increased. The fracture toughness increased first and then decreased with increasing SiC_p size, and when the SiC_p size was about 7 μm, the composites obtained the maximum fracture toughness value of 31.74 MPa m^1/2.     

TiNi形状记忆合金动态力学性能测试

随着TiNi形状记忆合金的开发和应用,其力学性能越来越受到重视。为了研究TiNi合金的力学性能,利用MTS万能试验机测试得到了TiNi合金不同温度下静态拉伸应力应力应变曲线,并对曲线进行了详细的分析;利用分离式霍普金森压杆(简称SHPB)对TiNi合金进行了多种高应变率下的动态压缩实验,得到了相应的应力应变曲线;利用改进的SHPB测试系统对TiNi合金进行了动态三点弯曲实验,得到了TiNi合金的动态断裂韧度。研究结果表明,TiNi合金不同于一般的金属,它的静、动态应力应变曲线出现了两个屈服平台、两个弹性阶段和两个非弹性变形阶段,同时,TiNi合金是一种比较脆的金属,在动态冲击载荷下容易发生脆断。     

热变形对TiNi形状记忆合金丝材力学性能以及超弹性的影响

通过拉伸测试Ф0．61mmTi-50．8at％Ni合金丝材退火后热拉拔过程中不同直径丝材的力学性能和弹性性能，研究了热变形对TiNi形状记忆合金丝材力学性能及超弹性的影响规律。结果表明，经过650℃退火后Ti-50．8at％Ni合金丝材超弹性较差，而断裂伸长率达50％以上。随着热拉拔变形量增大，超弹性逐渐提高，而塑性迅速降低，当热拉拔总热变形量达50％时，丝材可以获得优良的超弹性能，△σ值（Rell-ReL）为200-250MPa，残余应变小于0．1％。同时伸长率大于10％。     

冷拉过程中TiNbZr合金的微观组织和力学性能

研究了TiNbZr生物β钛合金的冷加工性能.TiNbZr合金由真空自耗电弧炉熔炼,实验过程中采用冷拉变形方式.在冷拉过程中,合金表现出良好的冷加工性能.当冷变形率在20%左右时,出现变形孪晶,使得合金强度有大幅度提高.在随后的冷变形过程中,位错滑移为主要的塑性变形方式.当冷变形率为80%时,抗拉强度达到1170 MPa,延伸率也大于10%.在该冷变形率下,晶粒得到显著细化,晶粒尺寸在20nm到50nm之间.     

Al-Si合金与HR-2钢热等静压直接扩散连接研究

采用热等静压直接扩散连接方法对Al-Si合金/HR-2钢进行了研究.检测了试样的气密性、界面结合强度,采用OM、SEM、EDS、AES分析连接界面的成分与组织.结果表明当扩散连接优化参数为T=540℃,P=120 MPa,t=1 h时,Al-Si合金/HR-2钢连接试样及试样焊接后的气密性均小于1×10-9 Pa-m3·s-1.试样连接界面形成明显的扩散层,界面紧密完整,未形成金属间化合物.连接试样的界面抗拉强度达56.3 MPa,压溃强度达112.5 MPa.     

钛镍多孔材料的制备及其显微组织与形状记忆性能

采用粉末烧结法制备了高孔隙率的Ti-50.8 at%Ni形状记忆合金(SMA),并对其显微组织和形状记忆性能进行了研究。结果表明,用该种方法制备的多孔合金样品具有孔隙分布均匀以及开孔率高的特点,其平均孔径在200μm左右。合金组织主要由奥氏体NiTi相(B2)和单斜马氏体NiTi相(B19’)组成。循环加载-卸载实验结果表明,该多孔材料能表现出一定的形状记忆效应,而且形状记忆效应随孔隙率的增加而降低。     

Powder Size Influence on Tensile Properties and Porosity for PM Ti_2AlNb Alloy Prepared by Hot Isostatic Pressing

Pre-alloyed powder of Ti_2AlNb alloy was prepared by electrode induction gas atomization method, and the powder was screened into fi ve kinds of powder size distribution. Fully dense Ti_2AlNb alloy was prepared by powder metallurgy(PM) using hot isostatic pressing. The properties of pre-alloyed powder and PM Ti_2AlNb alloy were tested. Results show that mean grain size of PM Ti_2AlNb alloy is infl uenced by powder particle size, but particle size has no signifi cant infl uence on tensile properties. Finer Ti_2AlNb powder has low Argon gas bubble ratio and high oxygen content, and poor fl owability of fi ner powder increases the degree of diffculty during degassing. As a result, big pores( 50 μm) are observed in PM Ti_2AlNb alloy prepared by fi ner powder and cause plasticity loss of tensile properties. In order to get a better comprehensive properties of PM Ti_2AlNb alloy, powder with an average size(～ 100 μm) is suggested.     

热等静压对铸造AlSi7Cu2Mg合金缺陷及性能的影响

采用砂型铸造AlSi7Cu2Mg铝合金阶梯形铸件,对不同部位试样进行等静处理,研究了不同热等静压压力(80~120 MPa)、时间(1~3h)对不同壁厚铸件缺陷及性能的影响。结果表明,随着热等静压压力增大和保压时间延长,不同壁厚铸件孔洞减少、密度提升,抗拉强度相应增大。铸件壁厚越大,密度和抗拉强度提升越明显;在热等静压温度(490℃)、压力(100 MPa)不变条件下,保温时间超过2h,铸件密度增加幅度较小;而在热等静压温度(490℃)、时间(2h)不变条件下,当热等静压压力超过临界值(100MPa)后,铸件抗拉强度提升不明显。     

热等静压Ti-6Al-4V钛合金热变形微观组织演变研究

采用Gleeble-1500热模拟试验机对热等静压态Ti-6Al-4V钛合金在温度950~1050℃、应变速率0.01~1s_-1条件下进行了热模拟压缩实验,研究了变形温度、应变速率对其显微组织的影响规律。结果表明：热等静压态Ti-6Al-4V钛合金在950℃以上变形后淬火组织以粗大的β晶粒与针状及板条马氏体组成,具有典型的β相区变形组织特征。β转变组织形成交错的网篮结构并具有特定的取向关系。变形过程中,发生了动态再结晶,并伴随着动态回复现象。在950℃、0.01s_?1条件下,以动态再结晶占据主导,得到均匀等轴β转变组织。随应变速率增大,以动态回复为主,β晶粒沿金属流动方向拉长,β转变组织得到细化。随温度升高,β晶粒变粗大,并仍然存在拉长变形带。同时,β转变组织有一定程度的粗化。     

部分热压法制备氮化硅多孔陶瓷研究

采用部分热压法,以Y2O3,MgO和CaO为添加剂,制备了气孔率在0.009～0.236的氮化硅多孔陶瓷.结果表明:制备的氮化硅多孔陶瓷是由众多长柱状的β-Si3N4晶粒及部分残余的α-Si3N4构成,气孔由长柱状的β-Si3N4搭接形成,其形状不规则.同时分析了氮化硅多孔陶瓷的力学性能与气孔率的关系,得出了气孔率与抗弯强度及断裂韧性的关系.     

TiNbZr合金在热处理过程中的微观组织和力学性能

TiNbZr合金由真空自耗电弧炉熔炼.研究了固溶,时效处理对该合金的微观组织和力学性能的影响.结果显示,当合金固溶处理1 h后在300和350℃时效处理时,合金的抗拉强度高达1000 MPa.当固溶后的合金在400和450℃时效处理时,出现α相.时效时间对α相的析出有重要的作用.当合金在400℃时效处理9 h后,抗拉强度为850 MPa,延伸率也保持在11%左右.