华南理工杨永强团队丨工艺对增材制造铝合金致密度、组织和力学性能的影响机理
1
研究背景及目的
增材制造技术为制造具有复杂形状的轻质部件提供了一种有效的解决方案。最近，高Sc含量的Al-Mg-Sc-Zr合金被用于选择性激光熔化工艺，以获得完全等轴晶粒结构并提高机械性能。但是，Sc是一种价格昂贵的稀土元素。随着该元素的添加量的增加，生产成本会急剧增加。因此，低Sc含量的Al-Mg-Sc-Zr合金的增材制造需要深入研究，以实现降本增效的目的。
2
论文亮点
1）开发了低Sc含量的Al-Mg-Sc-Zr合金的增材制造工艺，致密度高达99.2%。
2）建立了能量密度与成型质量的内在关系。
3）揭示了高能量密度下轻质合金熔池内匙孔形成的机理。
4）获得具有扇形特征的微观组织，抗拉强度高达451.1 MPa。
图1 增材制造过程中低Sc含量Al-Mg-Sc-Zr合金中匙孔形成机理示意图
3
试验方法
采用粉末床激光增材制造技术制造低Sc含量的Al-Mg-Sc-Zr合金，在激光功率300-400W和扫描速度400-800mm/s的范围内进行成型工艺探索。采用阿基米德排水法测试合金的密度；采用VHX-5000超精深显微镜测量合金零件的表面粗糙度；采用莱卡DMI5000M倒置式金相显微镜观察成型合金的微观组织形貌。采用HVS-30数字维氏硬度测试仪进行硬度测量。热处理是在马沸炉中进行，升温到325摄氏度后保温8小时，然后在空气中冷却。而热处理前后的拉伸性能通过CMT5205万能电子测试仪获取。
4
研究结果
6）时效处理后，抗拉强度和屈服强度分别提升了18.1%和41.3%，达到532.7 MPa和490.0 MPa。但是，断后延伸率略微降低到13.1%。
5
结论
6
前景与应用
本研究有助于具有复杂几何特征的高性能轻量化结构件快速制造，同时降低 制造成本，促进其在航空航天、汽车、船舶等领域中的应用。
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近年团队发表文章
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[2] Liu, Zixin, Yongqiang Yang, Di Wang, Jie Chen, Yunmian Xiao, Hanxiang Zhou, Ziyu Chen, and Changhui Song. "Flow field analysis for multilaser powder bed fusion and the influence of gas flow distribution on parts quality." Rapid Prototyping Journal ahead-of-print (2022).
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