Composition Optimization and Microstructure-Property Investigation of Al-3.0Ce-xCa-yMn Alloy Exhibiting High Hot Tearing Resistance

This study employs a combined approach of theoretical calculations and experimental validation to systematically optimize the alloy composition, aiming to mitigate the hot cracking susceptibility of an Al-3.0Ce-xCa-yMn alloy in laser powder bed fusion (LPBF) processing. Through advanced characterization techniques such as electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and mechanical property testing, the intrinsic relationship between microstructure and mechanical performance was thoroughly elucidated. Computational results revealed that the addition of Ca significantly lowered the eutectic precipitation temperature, thereby effectively reducing the hot cracking tendency while maintaining a stable volume fraction of the Al11(Ce, Ca)3 phase. The optimal mass fractions of calcium (Ca) and manganese (Mn) were determined to be 0.8% and 1.9%, respectively. Microstructural characterization indicates that the alloy consisted of an α-Al matrix embedded with Al-Ce-Ca ternary eutectic compounds, and nanoscale Al6Mn spherical precipitates were uniformly distributed within the matrix. Mechanical property evaluations demonstrated that the Al-3Ce-0.8Ca-1.9Mn alloy exhibited an outstanding balance of strength and ductility at both room and elevated temperatures, with room temperature yield strength, tensile strength, and elongation values of 321 ± 15 MPa, 429 ± 8 MPa, and 10.9 ± 2.3%, respectively. This exceptional performance was attributed to a synergistic combination of multiple strengthening mechanisms including eutectic structure-induced strengthening, grain boundary strengthening due to ultrafine grains, and dislocation pinning strengthening caused by nano-sized Al6Mn precipitates.