Laser Additive Manufacturing of Low-Cost Ti-Mo Alloys: Microstructural Evolution, Phase Analysis, and Mechanical Properties

Design and fabrication of low-cost biomedical Ti alloys has recently received considerable attention. Herein, additive manufacturing employing laser engineered net shaping (LENS) is used to fabricate low-cost Ti-5wt%Mo and Ti-10wt%Mo alloys from mixed elemental powders, and the resulting features are studied and compared with those of LENS-produced commercially pure Ti (CP-Ti). Optimization of the processing parameters shows that, on increasing Mo, densification is slightly reduced. Phase analysis and microstructural investigations on the Ti-Mo alloys show strong dependency on the level of Mo additions. CP-Ti sample exhibits an alpha phase microstructure with mainly coarse and some fine plate-like features, whereas addition of 5% Mo results in a mixture of acicular alpha ' distributed within beta phase grains. Addition of 10% Mo stabilizes the beta phase, while minor peaks indicating the presence of some omega phase are detected by X-ray phase analysis. Mechanical characterization reveals that Ti-10%Mo has the lowest elastic modulus due to its dominant beta phase structure as well as the highest microhardness and yield strength due to solid-solution strengthening effects from Mo and the presence of the nanoscale omega phase. However, the presence of the omega phase and the slightly lower densification also reduce the deformation strain in comparison to the Ti-5%Mo and CP-Ti.