Influence of quenched-in vacancies on the elastic modulus and its dependence on the temperature in β CuAlBe shape memory alloys

Abstract

The influence of quenched-in vacancies on the elastic modulus and its dependence on the temperature was studied in a β CuAlBe polycrystalline shape memory alloy. Samples with different quenching temperatures were submitted to different heat treatments and the behavior of the elastic modulus, phase transformation and microstructure with the temperature was carefully analyzed to understand the processes that occur in each stage. The quenched-in vacancies retained in β phase migrate during a heating from room temperature up to 200 °C and the modulus exhibits a two stage behavior, associated with the higher mobility of the quenched-in vacancies at higher temperatures. However, those present in martensite phase would not be eliminated during the first heating or subsequent heating cycles at 200 °C or 300 °C. Part of these vacancies would also produce the hyperstabilization of some amount of martensite phase.