Investigation of the Feasibility of a Novel Heat Stamping Process for Producing Complex-shaped Ti-6Al-4V Panel Components

Abstract

A novel cost-efficient Heat Stamping (HS) process, combining Heat treatment and fast Stamping, was proposed to produce complex-shaped titanium alloy panel components with low energy consumption and short cycle time. To investigate the feasibility of the HS process for forming Ti-6Al-4V, the stress-strain behaviours of the material under step quenching treatments in HS processes were investigated and compared with those under direct heating treatments in Hot Forming (HF) processes, through uniaxial tensile tests at the temperature range of 800 - 950 °C and the strain rate range of 0.01 - 5 /s. To reduce the strain softening, step quenching treatment was designed by soaking the specimen at 950 °C and fast quenching it to 800 °C for forming. It was found that strain softening in the step quenching tests was reduced as compared to direct heating tests at the strain rate of 1 /s; strain hardening was observed in step quenching test at the strain rate of 0.1 /s, achieved by enhancing the dynamic phase transformation from β phase to secondary α (αs) during deformation. Strain rate hardening of the material under step quenching treatment was found to be higher than those under direct heating treatment at the same temperature of 800 °C. To evaluate the novel HS concept, Heat Stamping experiments under step quenching treatments were carried out by using a drawability tool set. A cup-shaped demonstrator with the drawing ratio of 1.3 was produced to prove the feasibility of HS process.