Abstract
The microstructural evolutions of the laser melting deposited Ti-22Al-25Nb (at.-%) orthorhombic alloy in different solutions and during different aging treatments were quantitatively investigated. The volume fraction of aggregate precipitates and B2 grain size under different annealing temperatures and holding time had been measured using the image analysis software. The relationships among heat treatment, microstructure and microhardness were established. The experimental results indicate that all heat-treated microstructure exhibited a majority of Widmanstatten O phase precipitates within B2 grains and a minority of α2 phase at grain boundaries. The volume fraction of total precipitates for samples heat-treated with different schedules could be controlled in the range of 65–74%. On the premise of this volume fraction and constituent phases, the microhardness mainly depended on the size of precipitates, where the finer the precipitates within grains are, the higher the value of microhardness is. The maximum microhardness was 429 HV0.5 for samples which were solution-treated at 940°C for 0.5 hours and then aged at 760°C for 12 hours.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
