A quantitative model to determine the Ti content for crack-free AlCuMg alloy in laser powder-bed fusion

Abstract

A quantitative model for hot cracking prediction is essential for the composition design of non-castable AlCuMg alloys. In present work, the hot cracking prediction model of laser powder-bed fusion (LPBF) processed Ti-modified AlCuMg alloys was built on the basis of time-dependent nucleation theory and non-steady nucleation kinetics. The critical Ti content for crack-free AlCuMg alloy was calculated by this model and then manufactured successfully under the guidance of crack elimination strategy given by model simulation. The microstructure evolution of AlCuMg alloys with both inferior and superior Ti content to the critical value were investigated respectively in detail so that the effectiveness of model could be verified. The correlation among cooling rate, Ti content and Al₃Ti nuclei density was quantified and analyzed so that the formation of hot-tearing cracks could be discussed combined with microstructure evolution and crack susceptibility criterion. This model is promising for simplifying composition design work of high-strength aluminum alloys and further giving guidance on parameter optimization for LPBF manufacturing of non-castable Al alloys.