Microstructure and Mechanical Properties of Novel Ti-Al- Mn- W Alloy

A novel thermal- deformable Ti- 43Al- 3.5Mn-0.5W (at%) alloy was designed and fabricated. The microstructure characterization, room and elevated temperature tensile mechanical properties, oxidation resistance, and deformation capacity of the alloy were investigated. The results indicate that compared with Ti-42Al- 5Mn, the developed alloy has better strength, high temperature oxidation resistance and thermal deformation ability. The alpha(2) and beta(o) phases of the alloy have lower Mn content, which reduces the precipitation tendency of Mn-rich Laves phase near the service temperature. The evolution of the phases in the alloy can be generalized as follows: beta ->beta+alpha ->beta +alpha +gamma ->beta +beta(o)+alpha +alpha(2)+gamma ->beta(o)+alpha(2)+gamma, with the T gamma- solv approximate to 1250 degrees C, T-beta approximate to 1360 degrees C. The microstructure of the forged alloy is lamellar structure and a large number of beta(o) and gamma mixed phases at the lamellar interface. The high temperature strength of the forged alloy decreases obviously. Through two-step heat treatment, the high temperature strength and stability of the forged alloy are improved to a certain extent, which is mainly attributed to the increase in lamellar structure content and the refinement size of lamellar colonies. At 800 degrees C, the yield strength, tensile strength, and elongation of the forged alloy treated with 1260 degrees C/ 0.5 h/AC+ 800 degrees C/3 h/FC were 320 MPa, 555 MPa, and 16%, respectively.