激光选区熔化成形高温钛合金组织与力学性能研究

Study on Microstructure and Mechanical Properties of High Temperature Titanium Alloy Formed by Selective Laser Melting

采用激光选区熔化(SLM)技术作为高温钛合金成形工艺,研究了热处理温度对SLM成形高温钛合金组织、力学性能的影响规律。实验结果表明,随着输入激光能量的增加,成形合金内部的缺陷由不规则的未熔合缺陷转变为规则的球形孔洞缺陷,最优成形工艺参数如下:激光功率190 W、扫描速度560 mm/s、铺粉厚度0.03 mm和扫描间距0.06 mm。当热处理温度低于相变点时,合金表现为由板条α和β残余组织组成的网篮组织,且随着温度升高,合金显微组织中的板条α含量减少,其长宽比降低,部分板条α相逐渐球化;当热处理温度高于相变点时,合金中的网篮组织转变为魏氏组织。随着热处理温度的升高,合金的抗拉强度基本不变,屈服强度有所上升,塑性呈先降后升的趋势。995℃×2 h/AC热处理合金获得最佳的强度-塑性匹配,抗拉强度为972 MPa,屈服强度为774.5 MPa,延伸率为16%。

Selective laser melting(SLM)was used as the forming process of high temperature titanium alloy,and the influence of heat treatment temperature on the microstructure and mechanical properties of the SLM-formed high temperature titanium alloy was studied.The experimental results show that with the increase of input laser energy,the defects inside the formed alloy change from irregular unfused defects to regular spherical hole defects.The optimal forming process parameters include laser power of 190 W,scanning speed of 560 mm/s,powder layer thickness of 0.03 mm,and scanning spacing of 0.06 mm.When the heat treatment temperature is lower than the phase transformation temperature,the alloy exhibits basketweave microstructure composed of lathαandβresidual microstructure.In addition,the content of the lathαin the alloy microstructure decreases with the increase of temperature,its length-width ratio decreases,and part of the lath a gradually spheroidizes.When the heat treatment temperature is higher than the phase transformation temperature,the basketweave microstructure in the alloy is transformed into Widmanstatten microstructure.With the increase of heat treatment temperature,the tensile strength of the alloy is basically unchanged,the yield strength is increased,and the plasticity shows a trend of decreasing at first and then increasing.The best strength-plasticity matching of the alloy is achieved under the heat treatment conditions of 995℃×2 h/AC:the tensile strength is 972 MPa,the yield strength is 774.5 MPa,and the elongation is 16%.