Mechanical and functional properties of Fe-Mn-Si biodegradable alloys fabricated by laser powder bed fusion: Effect of heat treatment

This study examines the microstructure evolution as well as the mechanical and functional properties of Fe-Mn-Si alloys produced by LPBF and subsequent heat treatment. The as-printed microstructure is dominant by gamma austenitic phase where finer equiaxed grains are found in the printing plane with a preference of <102> orientation alignment with building direction. The segregation of Mn and Si at cell boundaries results in the precipitation of D0(3) (Fe3Si) phase. With increasing annealing temperature below 800 degrees C, the quantities of both epsilon martensite (having the orientation relationship of (111)gamma// (0002)epsilon and [011]gamma// [2 (11) over bar0]epsilon) and D0(3) precipitates (having the orientation relationship with the gamma austenite as ((11) over bar1)(gamma)// (20 (2) over bar )D03 and [011](gamma)// [111]D03) increase. Full recrystallization at higher temperature (900 degrees C) would eradicate as-printed microstructure characteristics and stimulate abundant annealing twins inside the austenite grains. The as-printed Fe-Mn-Si alloys exhibit anisotropic tensile behavior with superior values in the case of building direction parallel to the tensile direction, which is reduced with increasing annealing temperature and minimized by complete recrystallization at 900 degrees C. The shape recovery ratio rises to a maximum value at 650 degrees C but decreases with the onset of recrystallization at higher temperature due to the reduction of SFs. The co-culture test demonstrates the outstanding in vitro compatibility of the printed Fe-Mn-Si alloy, which may enhance osteoblasts' growth and promote the regeneration of bone tissue. The remarkable ability of Fe-Mn-Si alloys to form complex structures through LPBF, together with its outstanding overall mechanical properties and biocompatibility, provides a solid foundation for the advancement of biodegradable implant designs.