热处理工艺对激光熔化沉积制造JBK-75合金组织及性能的影响

采用激光熔化沉积技术制备JBK-75合金,选取750℃直接时效和1180℃高温固溶+750℃时效两种不同热处理工艺路线,分析了其沉积态的显微结构,对比两种不同热处理态的组织和力学性能。结果表明,沉积态JBK-75合金组织表现为各向异性,存在柱状晶、胞状组织和Ti元素偏聚。直接时效处理JBK-75合金打印组织未发生溶解,打印组织对强化相(γ′相)的析出行为几乎没有影响,但是Ti元素的偏聚促进了晶界有害相(η相)的生成。高温固溶+时效处理JBK-75合金打印组织消失,获得细小均匀的γ晶粒且在晶界未发现η相。高温固溶+时效处理激光熔化沉积JBK-75合金表现出最佳的强塑性配比,抗拉强度为1055 MPa、屈服强度为679 MPa、断后伸长率为29%,达到锻件JBK-75合金热处理态力学性能水平。     

Effects of Ni Content and Solution-Aging Treatment on Multi-Stage Transformations of TiNi Shape Memory Alloys

Effects of Ni content and solution-aging treatment on transformation type and transformation temperature of Ti100-xNix (x=33.3-75) alloys were investigated by differential scanning calorimeter (DSC). The results show that one-stage transformation B2→B19′ of the solution-quenched Ti100-xNix alloys occurs. The martensitic transformation temperature TM is constant at x = 40-49, decreases sharply at x = 49-52, increases gradually at x = 52-56, and is constant again at x = 56-70. The alloys after aging at 773 K for 3.6 ks and 36 ks will have the occurrence of one-stage transformation B2→B19′ at x = 40-50.5, and the TM is constant first and then decreases suddenly with increasing of x; when x = 50.5-52, the alloys have the occurrence of two-stage transformation B2→R→B19′ and the TM decreases gradually with increasing of x; when x=53-70, the alloys have the occurrence of three-stage transformation and the TM1 and TM2 all increase first and then keep constant with increasing of x. All alloys after aging at 773 K for 360 ks have the occurrence of one-stage transformation B2→B19′ except for Ti49Ni51 and Ti47Ni53 alloy, which will have the occurrence of two-stage transformation B2→R→B19′ and three-stage transformation, respectively