Influence of Ti60/Ti6554 ratio on the microstructure and properties of Ti alloys fabricated by laser directed energy deposition

Abstract

To develop high-strength and high-temperature Ti alloy, a series of new Ti alloys with different Ti60/Ti6554 ratios were designed under the guidance of an advanced cluster model, and then these alloys were fabricated by laser-directed energy deposition. The effects of Ti60/Ti6554 ratio on the microstructure and properties of the as-deposited alloys were investigated. The results show that all as-deposited alloys exhibit typical morphological characteristics of basket-weave microstructure. The difference is that the fraction and size of α lath gradually decrease with the increase of Ti60/Ti6554 ratio, which leads to a decreased room-temperature strength and an increased room-temperature ductility. However, the high-temperature strength and ductility show a diametrically opposite trend to room-temperature strength and ductility, having obviously dynamic softening characteristics. Increasing Ti60/Ti6554 ratio can effectively improve the high-temperature oxidation resistance. As predicted by the cluster model, the as-deposited alloy with Ti60/Ti6554 ratio of 5:5 has the best balance of room- and high-temperature mechanical properties and oxidation resistance among the studied alloys, being a promising candidate as high-strength and high-temperature Ti alloy.