激光选区熔化成形含锆Al-Cu-Mg合金的显微组织与力学性能

Microstructures and mechanical properties of Zr modified Al-Cu-Mg alloy processed by selective laser melting

采用激光选区熔化(Selective laser melting,SLM)技术制备含锆Al-Cu-Mg合金,通过SEM、EBSD、TEM、拉伸实验等方法研究沉积态和热处理态试样的显微组织与力学性能。结果表明:当激光能量密度为370 J/mm^(3)时,试样的致密度最高。原位生成Al_(3)Zr使试样的平均晶粒尺寸细化为1.28μm,消除了SLM成形Al-Cu-Mg合金中的热裂纹。尺寸为50~300 nm的Al_(3)Zr亚稳态相(L1_(2)-Al_(3)Zr)分布于基体,L1_(2)-Al_(3)Zr可充当α(Al)非均匀形核的有效衬底,与α(Al)晶面的错配度低,也能阻碍晶界迁移,抑制晶粒长大。工艺优化后,沉积态试样的室温抗拉强度为(369±9) MPa,伸长率为(12.4±0.6)%;T6热处理后,试样的抗拉强度提升至(485±10) MPa,伸长率略降为(11.2±0.5)%。细晶强化和弥散强化分别主导了沉积态和热处理态试样的强度提升。

Zr-modified Al-Cu-Mg alloy was processed by selective laser melting(SLM)technique.The microstructures and mechanical properties of as-deposited and heat-treated(T6)samples were systematically analyzed.The results show that samples with the highest density can be achieved when the energy density is 370 J/mm^(3).The in-situ formed Al_(3)Zr refines the grain size to 1.28μm and therefore eliminates the common hot tearing in SLMed Al-Cu-Mg alloys.The metastable phase of Al_(3)Zr(L1_(2)-Al_(3)Zr)with a size range of from 50 nm to 300 nm is observed,which is responsible for the grain refinement.L1_(2)-Al_(3)Zr particles act as the nucleus of heterogenous nucleation ofα(Al)due to their minimal mismatch.Besides,the L1_(2)-Al_(3)Zr particles can further refine the grains by hindering the migration of grain boundaries.The ultimate strength of(369±9)MPa and the elongation of(12.4±0.6)%are achieved for the as-deposited samples after process parameter optimization.After T6 heat treatment,the ultimate strength greatly increases to(485.2±10)MPa with a slight decrease in plasticity(elongation of(11.2±0.5)%).The strength enhancements of the as-deposited and heat-treated samples can be mainly attributed to the Hall-Petch strengthening and the Orowan strengthening mechanisms,respectively.