Influence of annealing treatment on the microstructure, mechanical performance and magnetic susceptibility of low magnetic Zr-1Mo parts manufactured via laser additive manufacturing

In recent years, a low magnetic and fully dense Zr-1Mo (wt%) part was successfully manufactured via the laser powder bed fusion (L-PBF) process, which shows the great potential as metallic biomaterials under the magnetic resonance imaging (MRI) environment. However, due to the high cooling rate after laser incident during the LPBF process, the as-fabricated Zr-1 Mo part consists of a non-equilibrium alpha' phase, which contributed to high strength (UTS: 1107 MPa) but insufficient ductility (elongation: 4.3%) for biomedical applications. In order to enhance the mechanical performance of as-fabricated Zr-1-Mo parts, various annealing processes that have been recognized as an efficient post-treatment to adjust the mechanical performance of additive manufactured products were executed. After the annealing process, acicular martensite alpha' microstructure in as-fabricated Zr-1Mo parts changed to stress relieved/partial relieved acicular alpha microstructure, basketweave alpha + beta microstructure, lamellar alpha + beta microstructure or retain alpha+ lamellar alpha + beta microstructure depending on different annealing conditions. In the meantime, elongation increased with increasing holding temperature and residence time, but the tensile strength exhibits a converse trend. The specimens annealed at 873 K, 803 K for 2 h and at 773 K for 8 h possessed UTS of 779 MPa, 964 MPa and 981 MPa as well as elongation of 14.3%, 11.0% and 9.6%, respectively. These annealing conditions could contributed to adequate strength and sufficient ductility, and should be the appropriate annealing conditions for Zr-1Mo parts produced by the L-PBF technology. By comparison with other conventional metallic biomaterials, annealed Zr-lMo alloy could be applied for the medical devices under MRI environments.

Automated summary

Various annealing processes were conducted to enhance the mechanical performance of as-fabricated Zr-1Mo parts, resulting in adequate strength and sufficient ductility for medical devices under MRI environments. The annealed Zr-1Mo alloy showed great potential as metallic biomaterials compared to other conventional materials.