热处理对增材制造TC4钛合金组织结构及耐蚀性能的影响

Effect of heat treatment on microstructure and corrosion resistance of TC4 titanium alloy manufactured by additive

增材制造TC4钛合金存在亚稳态相结构,其对合金的组织结构和耐蚀性有着明显的影响。基于此,对增材制造TC4钛合金进行了不同工艺的热处理,采用扫描电镜(SEM)、X射线衍射(XRD)、残余应力测量和电化学分析等研究了热处理对增材制造TC4钛合金组织结构、残余应力与耐蚀性能的影响。结果表明:热处理工艺对TC4钛合金的组织结构具有重要影响,当钛合金在940℃以上保温1 h后冷却,组织由亚稳态α′相转变为α+β相及少量次生α相,与炉冷相比,水冷条件下钛合金β相含量更高;当热处理温度为800、940和1080℃时,钛合金表面的残余应力值较低;钛合金的耐腐蚀性能与组织结构和残余应力有着密切关系,钛合金中α相晶粒越细小,β相含量越高,残余压应力值越大,其耐蚀性越好。当热处理温度为1020℃时,钛合金表面残余压应力值为470 MPa,耐蚀性能良好。

There is metastable phase structure in TC4 titanium alloy manufactured by additive,which has obvious influence on microstructure and corrosion resistance of the alloy.Based on this,the heat treatment of the TC4 titanium alloy manufactured by additive was carried out by different processes.The effects of heat treatment on the microstructure,residual stress and corrosion resistance of the TC4 titanium alloy manufactured by additive were studied by means of scanning electron microscopy(SEM),X-ray diffraction(XRD),residual stress measurement and electrochemical analysis.The results show that the heat treatment process has an important influence on the microstructure of the TC4 titanium alloy.When the titanium alloy is heat treated at above 940℃for 1 h and cooled,the microstructure changes from metastableα′phase toα+βphase and a small amount of secondaryαphase,and compared with furnace cooling,titanium alloy under water cooling condition has higherβphase content.When the heat treatment temperature is 800,940 and 1080℃,the residual stress on the surface of the titanium alloy is relatively low.The corrosion resistance of the titanium alloy is closely related to the microstructure and residual stress.The finer theαphase grain,the higher theβphase content,the greater the residual compressive stress and the better the corrosion resistance of the alloy.When the heat treatment temperature is 1020℃,the residual compressive stress on the surface of the titanium alloy is 470 MPa,and the corrosion resistance is good.