Structure–property relationships during high temperature deformation of Cu–4·5Ti alloy

Abstract

A Cu–4·5Ti (wt-%) alloy was subjected to hot compression tests at temperatures ranging from 750 to 900°C and strain rates from 10⁰ to 10^-3 s^-1. A hardness of 180 HV10 was observed after deformation at a low temperature of 750°C, at small as well as large strain rates, whereas the alloy deformed at high temperature (900°C) exhibited high hardness values, i.e. 300 HV10 at a strain rate of 10⁰ s^-1 and 280 HV10 at 10³ s^-1. Furthermore, a reduction in grain size from 110 µm at a strain rate of 10³ s^-1 to ∼55 µm at 10⁰ s^-1 was observed when the alloy was deformed at 900°C. Optical and SEM observations revealed a lamellar structure at 750°C, while equiaxed grains with some lamellar growth were seen in the alloy deformed at 900°C, at both strain rates. The difference in behaviour is attributed to the presence of equilibrium precipitate β-Cu₃Ti at 750°C, whereas it is almost absent at 900°C. The high hardness observed at 900°C is due to the formation of fine scale precipitation during air cooling of the deformed alloy.