Effect of micro-alloying elements on the microstructure and properties of Ti-1300 alloy fabricated by directed energy deposition

In this research, Al_0.5CoCrFeNi high-entropy alloy (HEA) multi-element micro-alloyed Ti-1300 alloy is fabricated by directed energy deposition. The microstructure, mechanical and electrochemical properties of Ti-1300 alloys are investigated. The average grain size of the Ti-1300 alloy is considerable reduced by 32.8% to 77.3 μm after micro-alloying. In addition, micro-alloying elements significantly improves the mechanical properties of the Ti-1300 alloy, with an increase in ultimate tensile strength of 13.4%, yield strength of 14.9% and average microhardness of 6.6%, while elongation remains essentially unchanged. Solution strengthening and refined crystalline strengthening are the dominant strengthening mechanisms. Electrochemical tests show that the micro-alloying elements results in a thicker and denser passivation film of Ti-1300 alloy in NaCl solution. This increases the resistance of the passivation film, leading to a reduction in both the corrosion current density and the corrosion rate. Multi-element micro-alloying is an effective strategy to improve the microstructure, mechanical and electrochemical properties of Ti-1300 alloy.