激光热力交互增材制造Ti6Al4V合金的组织及力学性能

Microstructure and Mechanical Properties of Ti6Al4V Alloy by Laser Integrated Additive Manufacturing with Alternately Thermal/Mechanical Effects

面向航空发动机关键构件长寿命高可靠性需求,针对增材制造中的“控形”和“控性”难题,结合塑性变形“逐层”消除内应力和冶金缺陷的思想,提出了激光热力交互增材制造新方法。基于该方法,以Ti6Al4V合金为研究对象,系统表征了成形件的残余应力和冶金缺陷分布、微观组织演变。并通过拉伸实验,研究了激光冲击处理(表面激光冲击强化和层间无吸收层激光冲击强化)对成形件力学性能的影响。结果表明,激光冲击处理使选区激光熔化(SLM)试样中的残余拉应力转变为残余压应力,并有效改善其内部冶金缺陷。同时,在激光冲击波作用下,粗的α’马氏体中产生了高密度的位错结构和大量2个方向的孪晶,共同促进了α’马氏体的晶粒细化。激光热力交互增材制造Ti6Al4V合金的极限抗拉强度和延伸率分别达到了1543 MPa和15.53%,相比于SLM成形件,分别提高了46.5%和91.5%,具有良好的强度和塑性匹配。

To meet the requirements of the long fatigue life and high reliability of the key components of the aeroengine as well as solve the challenges of“structure control”and“performance control”based on the fact that plastic deformation can effectively eliminate internal stress and close metallurgical defects generated by the thermal effect, a laser integrated additive manufacturing technology with alternately thermal/mechanical effects is developed. In this study, Ti6Al4V alloy was chosen as the research object. The distributions of residual stress and metallurgical defects and the microstructural evolution of the formed components were systematically studied. The effects of surface laser shock peening(LSP) and interlayer LSP without coating(LSPwC) treatments on mechanical properties were investigated using a tensile test.The results showed that after LSP, tensile residual stress was transformed into compressive residual stress. Additionally, laser shock waves could effectively improve the metallurgical defects in selective laser melting(SLM)-formed components. Moreover, high-density dislocation structures and numerous twins in two directions were produced in coarse α’ martensite by laser shock waves, which jointly promoted the grain refinement of α’ martensite. The ultimate tensile strength and elongation of Ti6Al4V fabricated by the laser integrated additive manufacturing technology with alternately thermal/mechanical effects reached 1543 MPa and 15.53%, which are 46.5% and 91.5% higher than those of the SLM-formed components, respectively, yielding a good combination of strength and ductility.