Influence of the addition of Cr in the microstructure and in the phase transformation temperatures of Cu–Al–Be–Nb–Ni alloys

Abstract

Cu–Al–Be polycrystalline SMAs modified with the addition of inoculants show improved ductility, which accredits them for technological applications. However, when the composition of these inoculants exceeds the solubility limit in the β matrix phase, precipitates occur which probably decrease the Be and/or Al content in the matrix, thus causing a change in the phase transformation temperatures. Thus, alloys that do not reach the desired phase transformation temperature need to be discarded and further processing must be performed, thereby generating additional costs in the alloy preparation process. In this sense, the main objective of this work is to investigate the influence of Cr addition on Cu–Al–Be–Nb–Ni alloys, with proportional variation of Cr and Be elements in CrBe 2 ratio, alloy grain refinement and temperatures of phase transformation. Additionally, the influence of the solubility temperature of the austenite, during tempering treatment, on the phase transition temperatures of these alloys was verified. The results obtained showed that the compensation of the Be content, added in CrBe 2 ratio, were efficient to maintain transformation temperatures close to the alloy without addition of Cr. It was also observed a considerable efficiency of the heat treatments in the reversion of the transition temperatures, being possible to obtain variations around 50\xa0°C after application of the heat treatment. In this way, it is concluded that the compensation of the Be content and modifications in the solubilization temperature is efficient in the process of control of the phase transitions.