Laser-Based Additive Manufacturing Processability and Mechanical Properties of Al-Cu 224 Alloys with TiB Grain Refiner Additions

This study investigated the impact of TiB grain refiner additions on the microstructural evolution, hot tearing susceptibility, and mechanical properties of Al-Cu 224 alloys to enhance their processing performance during the selective laser melting (SLM) process. A simple laser surface remelting method was utilized to simulate laser-based rapid solidification. The results revealed that the addition of appropriate amounts of TiB grain refiner could completely eliminate the solidification cracks during the laser surface remelting process. The introduction of TiB2 particles in the melt pools through the TiB grain refiner addition changed the grain morphology from a coarse columnar to a fine equiaxed structure, and the grain sizes were reduced from 13 to 15 mu m in the base alloys to 5.5 mu m and 3.2 mu m in the alloys with 0.34 wt% Ti (B-3TiB) and 0.65 wt% Ti (ZV-6TiB) additions, respectively. The hardness values of the modified B-3TiB and ZV-6TiB alloys reached 117 and 130 HV after a T6 heat treatment, which surpassed the hardness of conventional AlSi10Mg alloys by at least 15-30%. This improvement was attributed to the finer grains and nanoscale theta '/theta '' precipitates. The results demonstrate that the TiB grain refiner addition can significantly improve the processability and mechanical properties of Al-Cu 224 alloys for SLM applications, offering a promising solution to the challenge of high hot tearing susceptibility in high-strength aluminum alloys.