选区激光熔化增材制造高强度Al-Mg-Sc-Zr合金的微观组织与力学性能

Microstructure and mechanical properties of Al-Mg-Sc-Zr alloy prepared by selective laser melting

以气雾化预合金粉末为原材料,采用选区激光熔化(selective laser melting,SLM)成形制备Al-Mg-Sc-Zr合金。采用光学显微镜、扫描电子显微镜及室温拉伸实验等研究激光功率对合金缺陷、微观组织及力学性能的影响。结果表明,SLM成形Al-Mg-Sc-Zr合金具有细等轴晶和粗柱状晶交替出现的混晶组织,在细等轴晶区存在明显的元素偏析和部分Al_(3)(Sc,Zr)析出粒子钉扎晶界。当激光功率由260 W增大到380 W时,试样的孔隙率呈现先减少后增加的趋势,力学性能的变化趋势相反。在最佳激光功率300 W下,试样相对密度达99.4%,仅存在少量因液态金属供应不足造成的小尺寸圆形孔隙;抗拉强度、屈服强度与断裂伸长率分别为429.7 MPa、363.5 MPa和17.7%。经325℃时效处理10 h后,合金的抗拉强度、屈服强度与断裂伸长率分别达到530.1 MPa、506.4 MPa和9.0%。

Al-Mg-Sc-Zr alloy were prepared by selective laser melting(SLM)technology with gas atomization powders as raw materials.The effects of processing parameters on metallurgical defects,microstructure,and tensile properties of SLM-fabricated samples were investigated through optical microscope analysis,scanning electron microscopy analysis,and unidirectional tensile test at room temperature,etc.The results show that SLM-fabricated Al-Mg-Sc-Zr alloy is characterized with mixed grains structure in which fine equiaxed grains and coarse columnar grains alternate.It can be obviously found that element segregation in fine equiaxed grain region and precipitated Al_(3)(Sc,Zr)particles pin at the grain boundary.When the laser power increases from 260 W to 380 W,the porosity of the sample decreases first and then increases,while the changing trend of mechanical property is opposite.When the laser power is 300 W,the optimum parameter is obtained with the relative density reaching 99.4%.There are only a few small shrinkage pores in the sample due to the insufficient supply of liquid metal.The ultimate tensile strength,yield strength,and fracture elongation are 429.7 MPa,363.5 MPa and 17.7%,respectively.After aging treatment at 325℃for 10 h,the ultimate tensile strength,yield strength,and fracture elongation are 530.1 MPa,506.4 MPa and 9.0%,respectively.