Omega-Assisted Alpha Phase And Hardness Of Ti-5al-5mo-5v-1cr-1fe During Low Temperature Isothermal Heat Treatment After Laser Surface Remelting

The near-beta titanium alloy Ti-5Al-5Mo-5V-1Cr-1Fe (Ti-55511) was treated by laser surface remelting (LSR) with a series of holding times at 500 degrees C in order to study the growth behavior of u-assisted a phase and its effect on mechanical properties. Transmission electron microscope and hardness test was used to characterize different phases and surface property of different samples. Results show that only a small quantity of athermal omega phases precipitate from beta matrix at the remelted zone and there are incomplete collapsed {111}beta lattice planes at the beta/omega boundaries because Ti-55511 has low electron/atom ratio and high Al contents. So the athermal omega phase precipitated during LSR process has little effect on increasing surface hardness of Ti-55511. omega-Assisted nano-scaled a lamellas can be formed by the connection of some initial a phases at the early stage of low temperature isothermal heat treatment. And all the omega phase dissolved after 500 degrees C/10min. Further increasing of holding times will cause volume fractions increase of the nano-scaled a lamellas, resulting in gradually improving hardness of the alloy at the remelted zone. (C) 2017 Elsevier B. V. All rights reserved.