Phase transformation behaviours and mechanical properties of Ti6Al4V-0.55Fe alloy during continuous cooling

The phase transformation and mechanical properties of Ti6Al4V-0.55Fe alloy were investigated during the continuous cooling process. The curves of α phase precipitation exhibit a typical S-shaped pattern, which indicated that β→α phase transformation is a nucleation-growth-controlled process. The average activation energy is 231 kJ mol⁻¹ calculated by Kissinger–Akahira–Sunose method. The Avrami exponent during β→α transformation significantly changes with the increasing transformed volume fraction. It is found that the thickness of α phase lamellar decreased, while the strength and hardness increased with the increasing cooling rate. Moreover, the fracture morphology of the samples gradually changes from ductile fracture to brittle fracture under the cooling rate from 1 to 15 K min⁻¹, which illuminates that the plasticity of the alloy will decrease.