Effect of Adding Methods of Nucleating Agent on Microstructure and Mechanical Properties of Zr Modified Al-Cu-Mg Alloys Prepared by Selective Laser Melting

作者：Wang Kaidong; Liu Yunzhong^*; Zhan Qiangkun; Huang Bin

来源：ACTA METALLURGICA SINICA, 2022, 58(10): 1281-1291.

DOI：10.11900/0412.1961.2021.00075

• BEHAVIOR

Selective laser melting (SLM) technology is gaining increasing attention in the field of additive manufacturing. Al-Cu-Mg alloy parts manufactured using SLM technology exhibit significant advantages in lightweight design and the integrated formation of complex structural parts in the aerospace field. However, because of their wide freezing ranges, Al-Cu-Mg alloys have a high cracking tendency at a high cooling rate. SLM technology was used to prepare Zr-modified Al-Cu-Mg alloys in this study. AI,Zr particles were synthesized to directly add to Al-Cu-Mg alloy powders, and ZrH2 particles were chosen to form Al3Zr in-situ during SLM processes. The differences between the effects of adding Al3Zr particles directly and forming Al3Zr in-situ on the microstructures and the mechanical properties of SLMed Al-Cu-Mg alloys were analyzed. The results show that the common hot tearing in as-built Al-Cu-Mg alloys all disappear due to the addition of AI,Zr nucleating agent and the in-situ formed AI,Zr is more conducive to refining grains and improving the plasticity and the processing efficiency of SLMed Al-Cu-Mg alloys. When the laser energy density is 370 J/mm(3), the grain size of the samples containing Al3Zr and in-situ formed AI,Zr particles are 1.88 and 1.28 pm, respectively. L1(2)-AI,Zr and undissolved or unmelted Al3Zr particles are the nucleation particles generated by initial AI,Zr particles; whereas, they are all metastable Al3Zr (L12-AI,Zr) synthesized in-situ. L1(2)-AI,Zr has a better nucleation ability than initial AI,Zr particles. The ultimate strength of the heat-treated samples with initial AI,Zr particles or in-situ formed AI,Zr can reach (493 2) or (485 10) MPa, respectively. The elongation of the samples with the in-situ formed Al3Zr is more than 30% higher than that of the samples containing Al3Zr particles. SLMed Al-Cu-Mg alloys with in-situ formed Al3Zr are more suitable for medium-high-speed processes because strong Marangoni flow aroused by high laser energy density is unnecessary for in-situ formed Al3Zr to realize the dispersion of the grain refiner.