Effect of γ2-phase precipitates on the martensitic transformation of a β-CuAlBe shape memory alloy

The influence of γ2 precipitates on the MT of a Cu–22.66Al–2.98Be (at%) polycrystalline alloy was analysed by compression test, differential scanning calorimetry and microscopy. As the precipitate content (or size) increases, the stress-induced martensitic transformation occurs at higher stress levels. The thermally induced martensitic transformation is only significantly affected when the γ2 phase content exceeds 14%, the thermal peaks are shifted to higher temperatures and less β phase transforms to martensite. TEM observations suggest good coherency between both phases, and dislocation bundles remain in the β side of the γ2/β interface after the compression-induced transformation to martensite. The evolution of σs with fvγ2 is analysed considering a chemical and a mechanical contribution.