不同热处理对SLM TC4组织性能及各向异性的影响  

Effect of Different Heat Treatments on Microstructure, Properties, and Anisotropy of SLM TC4

作　　者：窦振 王豫跃[1] 张安峰[2] 吴梦杰 王普强 Dou Zhen;Wang Yuyue;Zhang Anfeng;Wu Mengjie;Wang Puqiang(State Key Laboratory for Mechanical Behavior of Materials,Xi’an Jiaotong University,Xi'an 710049,Shaanxi,China;State Key Laboratory for Manufacturing Systems Engineering,Xi’an Jiaotong University,Xi'an 710054,Shaanxi,China)

机构地区：[1]西安交通大学金属材料强度国家重点实验室,陕西西安710049 [2]西安交通大学机械制造系统工程国家重点实验室,陕西西安710054

出　　处：《中国激光》2022年第8期91-102,共12页Chinese Journal of Lasers

基　　金：国家自然科学基金(51775417);国家重点研发计划(2016YFB1100102)。

摘　　要：选区激光熔化(SLM)成形的TC4样件强度高、塑性差、各向异性明显。对SLM TC4成形件进行固溶时效、循环退火、循环球化退火+固溶时效三种热处理,采用光学显微镜、扫描电子显微镜、拉伸试验机对热处理所得成形件进行组织观察和性能测试。研究表明SLM TC4成形件微观组织由马氏体α′和马氏体α″组成,强度为1220MPa左右,延伸率最高达13%;TC4成形件经热处理后板条α相粗化,有等轴α相产生,板条状α相长宽比降为5左右,固溶时效处理和循环球化退火+固溶时效处理的TC4成形件组织中产生二次α相;先950℃固溶1h,之后550℃保温4h,此条件下所得成形件的综合力学性能最好,其抗拉强度达到957.9 MPa,延伸率为17.6%,且所有拉伸性能指标的各向异性小于1.2%;循环球化退火+固溶时效处理的样件塑性很高,延伸率达18.3%,同时强度的各向异性不超过2%,固溶时效与循环球化退火+固溶时效处理后力学性能超过国家锻件标准。经过循环退火处理的TC4成形件强度损失较大,但塑性与另外两种热处理工艺相差不大。Objective Ti-6Al-4V(TC4)titanium alloy exhibits impressive characteristics,including excellent corrosion resistance,high specific strength,and yield ratio,and thus,widely used in several fields,such as aerospace,navigation,and biomedical industries.Selective laser melting(SLM),a common method for manufacturing metal alloys,has multiple advantages,such as short production time,low cost,high integration,and high precision.Therefore,SLM is preferred for the fabrication of TC4alloys with high density and good mechanical properties.However,the molten pool of SLM undergoes rapid melting and solidification under high temperature gradient.The microstructure of SLM TC4is mainly composed ofβcolumnar crystals,imparting poor plasticity and obvious anisotropy to the samples.Therefore,the deposited samples fail to meet the standard of commercial engineering and the simulation requirements of the titanium alloy.In this study,the TC4 samples prepared by SLM were heat-treated under three different conditions of solution aging,cyclic annealing,and cyclic spheroidizing annealing with solution aging.The effects of the three heat treatments on the microstructures and mechanical properties of the deposited TC4were investigated with an optical microscope,a scanning electron microscope,and a tensile strength testing machine.The mechanisms of change in the microstructure and anisotropy during the three heat treatments are analyzed,providing a research basis for the application of TC4in the aerospace field.Methods In our study,TC4alloy powder with the particle size of 15--65μm was used along with the rolled TC4 substrate.Before the experiment,the powder was placed in an oven and dried at 120°C for 24hto remove the moisture from the powder.The formation process and heat treatment were performed in the argon gas atmosphere.The size of the horizontal sample was 45 mm×8 mm×8 mm,while that of the vertical specimen wasΦ8 mm×45mm.According to the national standard GB/T228.1--2010,the samples were processed into standard tensile specimens

关 键 词：激光技术 选区激光熔化 TI-6AL-4V 热处理 微观组织 力学性能 各向异性 

分 类 号：O436[机械工程—光学工程]