Advances in obtaining refined equiaxed grains for additively manufactured titanium alloys

Abstract:

Titanium alloys are prevalently applied in aerospace, ship, and medical fields due to their excellent properties such as high special strength, corrosion resistance, and biocompatibility. Additive manufacturing technology provides a revolutionary way for processing the integrate and light-weight parts with short cycles. However, the coarse columnar grains produced in the forming process lead to the anisotropy of the components, which limits the full play of the properties for the alloys. To control the size and morphology of the grains is the hotspot in recent years. This study briefly describes the feature and formation mechanism of typical grain microstructures in general additive manufacturing methods, expounds grain-control methods in parameters optimization, novel processing methods, micro-alloying/new alloy composition design, subsequent heat treatment, external field assistance, and the combination of these methods. The grain regulation mechanisms are summarized and the control effects are evaluated. Most of the control methods can obtain full-equiaxed grains and weaken the anisotropy of mechanical properties in the room-temperature tensile test. Subsequent treatments and mechanical properties evaluation of the obtained equiaxed microstructure alloys are expected to achieve the target properties and engineering application through further research.

Key words:Additive manufacturing; Titanium alloys; Grain control