扫描策略对SLM AlCoCrFeNi_(2.1)共晶高熵合金开裂敏感性的影响

Effect of scanning strategy on cracking sensitivity of SLM AlCoCrFeNi_(2.1) eutectic high-entropy alloy

采用有限元仿真和试验相结合的方法从宏观分析了不同扫描路径对选区激光熔化成形AlCoCrFeNi_(2.1)共晶高熵合金试样开裂敏感性的影响。研究发现,棋盘格扫描路径具有更小的动态应力值和残余应力,其残余应变导致试样呈现“内缩外拱”趋势,而长直线扫描路径产生的残余变形导致试样上拱趋势更加明显,但上表面更加平整。另外,试验发现低能量密度下由于欠熔合引起的不规则缺陷造成的应力集中远大于由于过熔合引起的球形缺陷造成的应力集中,试样开裂敏感性随着输入能量密度的升高而逐渐降低。长直线扫描路径成形试样的裂纹自试样底部中间向上扩展并向上翘起,而棋盘格扫描路径打印的试样则自试样的对角开裂并向上翘起,与仿真结论保持一致。本文研究结果可为深入理解选区激光熔化技术成形AlCoCrFeNi_(2.1)共晶高熵合金的宏观开裂机制和推动该合金的工程化应用提供参考。

In this paper,the cracking mechanism of AlCoCrFeNi_(2.1)eutectic high-entropy alloy samples formed by selective laser melting with different scanning paths is analyzed at the macroscopic level using a combination of finite-element simulation and experimental methods.In comparison with the long linear scanning path,it was found that the tessellated scanning path has smaller dynamic and residual stresses,and its residual strain leads to the tendency of“inward shrinkage and outward arching”of the specimen,while the residual deformation generated by the long linear scanning path leads to the tendency of upward arching of the specimen,which is more obvious,but the upper surface is more flat.In addition,the stress concentration due to irregular defects caused by underfusion at low energy density is much larger than that due to spherical defects caused by overfusion,which results in a gradual decrease in the cracking susceptibility of the specimen with the increase of input energy density.The stress-strain distributions caused by different scanning paths are consistent with the simulation conclusion that the cracks in the specimens shaped by the long straight scanning path expand upward from the bottom center of the specimen and warp upward,whereas the specimens printed by the tessellated scanning path crack diagonally and warp upward,which is consistent with the simulation conclusions.This paper provides a reference for a deeper understanding of the macroscopic cracking mechanism of AlCoCrFeNi_(2.1)eutectic high-entropy alloy shaped by selective zone laser melting technology and promotes the engineering application of this alloy.