Effect of heat treatments on microstructure and mechanical behavior of laser welded LPBF AlSi10Mg alloys

Abstract

In this work, heat treatments were performed on autogenously laser welding of laser powder bed fusion (LPBF) AlSi10Mg alloys to improve mechanical properties of welded joints. After welding, the welded joint was heat treated by direct aging (DA) and solution heat treatment and artificial aging (T6) treatment. The porosity, microstructure and mechanical performance of the welded joints after DA and T6 treatments were investigated and compared with the as-welded joint. Results show that the microhardness of weld metal (WM) has been increased to over 93.5 HV0.1 after DA treatment, while the microhardness in the T6 welded joint is reduced to 77.0 HV0.1, from 82.0 HV0.1 in the as-welded joint. The ultimate tensile strength (UTS) of the DA treated joint reaches 276.5 MPa, showing an increase of 43.0% compared with as-welded joint. The DA heat treatment of the LPBF AlSi10Mg welded joints effectively improves the hardness and the UTS, which can be mainly attributable to the reduction of the hydrogen pores, the enhancing effect of solid solution strengthening coming from the Si element in the Al matrix and the dispersion strengthening of Si precipitation.