Hot isostatic pressing of laser powder bed fusion AlSi10Mg: parameter identification and mechanical properties

The fatigue crack initiation of as built (AB) laser powder bed fusion (LPBF) AlSi10Mg is highly affected by the presence of large porosities inherent to the process. Hot isostatic pressing (HIP) is a potential means of reduction of this detrimental porosity. Classic high temperature HIP treatments at about 500 °C and 100 MPa pressure lead to significant strength loss that is partially recovered after additional solution and ageing heat treatments, i.e. overall a three-step treatment. In this work, a 350 °C HIP treatment performed under a higher pressure of 300 MPa for 2 h has been identified as a promising post-treatment for LPBF AlSi10Mg using finite element method simulations of the HIP process. This treatment is shown to suppress these large porosities and lead to higher fracture strain and total fatigue life than after the classic three-step treatment (HIP + two steps of heat treatment). Both HIP treatments also present higher fracture strain compared to the AB material. Thus, this new 350 °C HIP treatment efficiently removes the need for post-treatments after HIP. The 350 °C at 300 MPa HIP treatment improves the yield strength weighted fatigue resistance compared to the AB material but not the absolute fatigue life.