Stress-induced martensitic transformation in polycrystalline aged Cu–Al–Mn alloys

Two polycrystalline Cu–Al–Mn alloys, namely Cu–13.5Al–4.5Mn, Cu–12.4Al–5.03Mn (wt.%) were investigated. Small (5–10 nm in size) coherent inclusions of Cu2MnAl phase precipitated during the austenite aging of Cu–Al–Mn alloy in a (Cu–Mn)3Al matrix. The characteristic temperatures, hysteresis of martensitic transformation, and value of superelastic deformation depend on the composition of alloys, size and volume fraction of the disperse inclusions. Mechanical tests of the samples were performed under simultaneous registration of electrical resistance and low-field magnetic susceptibility dependence on the strain value. In case of aged Cu–Al–Mn, a change in magnetic properties of the ferromagnetic inclusions related to the stress-induced martensitic transformation of the surrounding matrix can be observed. The maximum value of superelastic deformation corresponds to the minimum width of the temperature hysteresis of martensitic transformation. The influence of coherent precipitates on mechanical properties of Cu–Al–Mn alloy has been analyzed in case of martensite crystals induced by the mechanical stress.