脉冲TIG增材修复TB6钛合金组织和性能优化

Optimization of microstructure and properties of TB6 titanium alloy repaired by pulsed TIG additive manufacturing

采用脉冲钨极惰性气体保护焊(TIG)增材制造技术对TB6钛合金进行缺陷修复,研究工艺参数(脉冲电流和脉冲时间)和热处理对修复后TB6钛合金微观组织和力学性能的影响,以确定最佳的热处理工艺参数。结果表明:在脉冲电流为50 A,脉冲时间为40 ms时,修复状态下TB6钛合金的力学性能相对较好,抗拉强度为1113 MPa,伸长率为5.26%。对样品依次进行固溶和时效热处理,在不同温度(740,760,780℃)下固溶2 h后,初生α相逐渐溶解,而β相生长并均匀分布在基体中。水淬后,β相的生长受到抑制,β晶粒内析出针状的斜方马氏体α''相,导致抗拉强度下降,伸长率显著提高。在不同时效温度(500,520,540℃)下保温8 h,α''相不断生长,逐渐转变为等轴晶粒,力学性能显著提高。在780℃/2 h WC+520℃/8 h AC条件下获得最佳的组织和力学性能,抗拉强度为1119 MPa,伸长率为7.36%。

The defects on TB6 titanium alloy were repaired using pulsed TIG(tungsten inert gas)additive manufacturing technology,and the effects of process parameters(pulse current and pulse time)and heat treatment on the microstructure and mechanical properties of the repaired TB6 titanium alloy were studied to determine the optimal heat treatment process parameters.The results show that the mechanical properties are relatively better in the as-repaired state when the pulse current is 50 A and the pulse time is 40 ms,with a tensile strength of 1113 MPa and an elongation of 5.26%.These samples are sequentially subjected to solid solution and aging heat treatment.When the samples are solid solution treated for 2 h under different temperatures(740,760,780℃),the primaryαphase is increasingly dissolved,while theβphase gradually grows and evenly distributes in the matrix.After water quenching,the growth of theβphase is inhibited,and acicular rhombic martensiteα''phase is precipitated inβgrains,resulting in a decrease in tensile strength and a remarkable increase in elongation.Under different aging temperatures(500,520,540℃)for 8 h,theα''phase continuously grows and gradually transforms to equiaxial grain,and the mechanical properties are greatly improved.The optimal microstructure and mechanical properties are achieved under the conditions of 780℃/2 h WC+520℃/8 h AC,with a tensile strength of 1119 MPa and an elongation of 7.36%.