Grain refinement of 316L stainless steel through in-situ alloying with Ti in additive manufacturing

Abstract

Additive manufacturing (AM) is a transformative approach to fabricating metal components in the industry. However, it is challenging for fusion-based AM to fabricate metallic materials, particularly austenitic stainless steels, which have fine equiaxed grains without the formation of undesirable intermetallic phases due to its intrinsic high thermal gradient and fast cooling rate. This work demonstrates that using in-situ alloying with Ti addition can significantly promote grain refinement (from 16.7 to 0.8 μm) without bringing undesirable intermetallic phases in selective laser melted 316L. The Ti-rich solutes at the solid/liquid interface activated heterogeneous nucleation, thus achieving grain refinement. The ultimate tensile strength (UTS) was enhanced from 704 MPa for 316L to 817 MPa for 316L-1.5Ti. The selection of grain refiner for different alloys was discussed. This methodology would be applicable to other alloys, such as Al alloys and Ti alloys, in order to tailor their microstructures and mechanical properties to suit specific engineering applications.