Deformation Heating and Temperature Changes in a Near-β Titanium Alloy during β-Processed Forging

Abstract

We investigated the temperature increase caused by heat generation from plastic deformation during β-processed forging in a near-β titanium alloy, Ti-17 alloy (Ti-5Al-2Sn-2Zr-4Cr-4Mo, wt%), by inserting thermocouples into large workpieces (100 mm in diameter and 50 mm in height). The workpiece was initially heated and held at 1193 K (920 °C) in the single-β region. It was subsequently forged between hot dies in surrounding heaters at a compression percentage of 75% at strain rates of 0.05 and 0.5 s−1 at 1023–1123 K in the (α + β) region. At 0.05 s−1, the temperature logarithmically increased by 39 K in 28 s for 1023 K; it increased by 30 K in 28 s for 1073 K. However, at 0.5 s−1, the material temperature increased, in 3 s, beyond or close to the β-transus temperature during forging at 1023 and 1073 K. In addition, as the forging temperature decreased, the increase in material temperature moderated, resulting in a difference of 27 K in the last forging stage, between the conditions of 1023 and 1073 K. This would reduce the temperature difference effect on microstructure formation during β-processed forging.