Effect of germanium alloying on microstructure and properties of Ti-6Al-4V alloy fabricated by additive manufacturing

The microstructure of Ti-6Al-4V titanium alloy produced by laser additive manufacturing is generally relatively coarse, so its mechanical properties have not yet achieved satisfactory results. After adding germanium element to titanium alloy, second phase particles can be formed, at the same time, due to strong bonding force between Ti and Ge atoms, there also have other strengthening effects that need to be revealed. Therefore, the effect of Ge addition on the microstructure and mechanical properties of additive manufactured Ti-6Al-4V alloy was studied in detail in this paper, which can provide more reference for optimizing the performance of titanium alloy manufactured with additives manufacturing. The pure Ge powder was ball milled with Ti-6Al-4V powder in several different proportions, and bulk samples were prepared by laser deposition manufacturing (LDM) with the mixed powder. The Germanium alloyed Ti-6Al-4V alloy's tensile strength and plasticity at room temperature increased about 25% and 10%, respectively, compared with LDMed Ti-6Al-4V alloy without Ge. According to the results of TEM and EDS, Ti and Ge reacted to form granular second phase Ti5Ge3, which distributes along the primary beta grain boundary inhibit the growth of columnar crystals. Part of Ge solutes into alpha phase. Both microstructure refinement and solid solution are very effective in impeding the moving of dislocation, so that the Germanium alloyed LDMed Ti-6Al-4V alloy showed excellent tensile property at room temperature.