Effect of heat treatment and exposure on microstructure and mechanical properties of Ti-25V-15Cr-2Al-0.2C (wt%)

The effect of heat treatment and exposure on the microstructure and mechani cal properties of extruded, bum-resistant beta titanium alloy Ti-25V-15Cr-2 Al-0.2C (wt%) has been studied. It has been found that pre-exposure anneali ng at 600, 700 and 800 degreesC affected the distribution of alpha phase th at precipitated following subsequent exposure at temperatures between 450 a nd 550 degreesC. Samples annealed at 600 degreesC and subsequently exposed at 450 degreesC showed excellent microstructural and property stability. Al though the room-temperature ductility of the alloy decreased and the streng th increased slightly with increasing exposure time at 500 degreesC, no fur ther drop in ductility was observed after 500 It. However, a gradual degrad ation of properties with exposure time was observed in samples exposed at 5 50 degreesC. The significance of the observations is discussed in terms of the effect of pre-exposure annealing and exposure on alpha precipitation an d tensile properties. (C) 2001 Acta Materialia Inc. Published by Elsevier S cience Ltd. All rights reserved.