Effects of quenching process on microstructure, mechanical properties and magnetic susceptibility in Zr1Mo alloy fabricated by powder bed fusion process

Abstract

In order to depress the “susceptibility artifacts” in magnetic resonance imaging (MRI), improve the mechanical reliability for biomedical structural applications and realize tailor-made medical devices with complex shape, low magnetic Zr-1Mo(wt%) alloy builds with high relative density (c.a. 99.9%) fabricated by laser powder bed fusion process(L-PBF) were subjected to various heat treatment conditions followed by water quenching. After quenching process acicular α′ microsturcture in as-build Zr-1Mo(wt%) alloy builds changed to basket weave α + β structure, unique retained α + ultra fine (α′ + α″) martensite structure or retained α + acicular α′ microsturcture depending on quenching conditions. X-ray diffraction (XRD) and high resolution-transmission electron microscope(HR-TEM) revealed a unique retained α + ultra fine (α′ + α″) martensite microstructure in 1123 K specimens. The stress-induced competition between β to α′ transformation and β to α″ transformation contributed to this unique microstructure. This unique microstructure contributed to a good balance between strength (UTS:822 MPa) and ductility (Elongation:11.7%). The volume magnetic susceptibility of quenched Zr-1Mo(wt%) alloy builds maintained low(about 1.01 × 10−4) indicating good MRI compatibility. The magnetic susceptibility of each phase was modified to be χα″ > χβ > χα > χα′ > χω. Zr-1Mo(wt%) alloy quenched from 1123 K will be an promising candidates for tailor made devices under MRI environments. Keywords: Powder bed fusion process, Zr-based alloy, Quenching process, Microstructure, Magnetic resonance imaging compatibility