Effect of α-Platelet Thickness on the Mechanical Properties of Ti-6Al-4V Alloy with Lamellar Microstructure

Abstract

In this paper, lamellar microstructures with average α-platelet thicknesses ranging from 0.55 μm to 1.98 μm were obtained in Ti-6Al-4V (Ti64) alloy by solution-treated above β-transus temperature and followed cooling through different methods. Then effects of the average thickness of plate-like α phase on the mechanical properties of this alloy were investigated. The results show that the yield stress and/or the flow stress of Ti64 decrease with increased average α-platelet thickness during compression under various strain-rate and temperature conditions. Conversely, the ductility increases with increased average α-platelet thickness. The greater plate thickness facilitates slip and avoids severe pile-up of dislocations in α phase, resulting in the augmentation of the fracture strain as well as decrease of the strength of Ti64. Finally, the variation of yield stress with average α-platelet thickness satisfies Hall-Petch relationship at both quasi-static and dynamic loading strain-rates.