Multistep low-to-high-temperature heating as a suitable alternative to hot isostatic pressing for improving laser powder-bed fusion-fabricated Ti-6Al-2Zr-1Mo-1V microstructural and mechanical properties

Laser-powder-bed-fusion (L-PBF) is a subset of additive manufacturing (AM) that has been increasingly used to manufacture titanium components for aerospace applications. However, titanium components fabricated by LPBF exhibit high mechanical strength and poor ductility because of refined alpha' martensite. Postheating is frequently used to transform the martensitic microstructure into equilibrium alpha phase for achieving the desired mechanical properties. In this study, superior strength and ductility were achieved by applying low-to hightemperature (LHT) multistep heating to Ti-6Al-2Zr-1Mo-1V (TA15) samples that were as-fabricated (AF) through L-PBF. For comparison, TA15 samples were subjected to one-step annealing and hot isostatic pressing (HIP). The L-PBF AF microstructure mainly comprised acicular alpha' martensite and exhibited high strength (1383 +/- 9 MPa) and low ductility (6.3 +/- 0.2%). Conventional one-step annealing formed lamellar alpha+beta microstructures that exhibited decreased strength (896-1182 MPa) and improved ductility (12.0-14.3%) compared to AF. Hot isostatic pressing (HIP) treatment formed a lamellar alpha+beta microstructure that exhibited a strength of 1015 +/- 30 MPa and ductility of 15.9 +/- 0.8%. LHT formed a trimodal microstructure comprising lamellar, equiaxed, and short-rod alpha and provided well-balanced strength (1033 +/- 4 MPa) and ductility (16.6 +/- 0.5%), which are superior than those of the samples prepared by using one-step annealing or HIP. Therefore, LHT is a suitable replacement for HIP to prepare L-PBF TA15 exhibiting superior mechanical properties for aerospace applications.