Microstructure, Densification and Mechanical Properties of Ti-22Al-25Nb Alloy Fabricated by Spark Plasma Sintering

摘要

The present study deals with the preparation of the powder metallurgy (P/M) Ti-22Al-25Nb (at.%) alloys with fine microstructure from pre-alloyed powders by spark plasma sintering (SPS). The SPS process was carried out at temperatures ranging from 950 to 1200 degrees C with pressures range of 35-80 MPa for 10-20 min followed by furnace cooling. The effects of SPS parameters on the microstructure, densification, phase composition and mechanical properties of the P/M Ti-22Al-25Nb alloys were discussed. The results revealed that all the SPS alloys were composed of B2 grains and O phases in the B2 grain interior, and a small amount of alpha(2) phase mainly distributed along B2 grain boundaries. The P/M Ti-22Al-25Nb alloy sintered at 950 degrees C/80 MPa/10 min exhibited the best combination of mechanical properties at room temperature with the elongation, yield strength and tensile strength of 9.38%, 933.57 and 990.01 MPa, respectively. In addition, the fracture mechanism at room temperature of the P/M Ti-22Al-25Nb alloy sintered at 950 degrees C/80 MPa/10 min was determined to be a mixed fracture mechanism with a combination of brittle fracture and ductile fracture.