Deciphering phase stress partition and its correlation to mechanical anisotropy of laser powder bed fusion AlSi10Mg

Abstract

Laser powder bed fusion AlSi10Mg exhibits severe mechanical anisotropy, which hinders its applications in industrial field. In the present work, we investigated the mechanisms of anisotropy in the light of phase stress partition, using traditional crystal plasticity and mechanism-based strain gradient crystal plasticity models. Two representative volume elements of the Al-Si cellular structures, corresponding to 35 ℃ and 200 ℃ build platform temperatures, were built to assess the influences of Al matrix strength and strain gradient on phase stress partition and anisotropy. In addition, the maximum principal stress distribution of the Si-rich network was probed, based on which the potential damage sites and densities were evaluated. The results show that the anisotropic strength and damage both originate from the elongated Si-rich network. According to the comparison between the 35 ℃ and 200 ℃ materials, an increase in Al phase strength can change the phase stress partition and effectively mitigate the anisotropy degree. Moreover, it is revealed that the strain gradient tends to alleviate anisotropy and delay damage evolution. The findings of this work can pave the way to developing high-performance LPBF Al alloys with lower degrees of anisotropy.