Mechanico-Thermal Treatment of Cu-7.5 at%Ni-2.5 at%Al Alloy

Abstract

Mechanico-thermal treatment (MTT) is one of the effective methods to improve mechanical properties of alloys. In the present study, an improvement in mechanical properties of Cu-7.5 at%Ni-2.5 at%Al alloy by MTT was undertaken in comparison with those of simply aged specimens.
By MTT, hardness, 0.2% proof stress (σ_0.2) and ultimate tensile strength (UTS) have increased at room temperature, and arrived their maximum values by ageing for a remarkable shorter time than those of simply aged specimens. The important point is that σ_0.2, UTS and total elongation are much improved at the elevated temperature as high as 500°C.
To study the origin of strengthening by MTT, thin foils were observed in a transmission electron microscope. In MTT specimens, the deformed structure disappeared perfectly and recrystallized to fine grains by ageing at 500°C for 0.1hr. In contrast with simply aged specimens, very small precipitates were observed within these grains, and the discontinuous precipitates around grain boundaries were scarcely observed. These characteristics in the microstructure would contribute to the strengthening of MTT specimens.