Reduction of Martensite Stabilization and Refinement of the Transformation Temperature Formula in Cu–Zn–Al–Ni Alloys

Abstract

Cu-Zn-Al alloys exhibit properties suitable for various technologicalapplications which are limited by stabilization of the martensite phase. It hasbeen established that by introducing a fourth alloying element, thisstabilization can be reduced. In this work, the effect of Cu substitution withcontrolled amounts of Ni in a Cu-16 at%Zn-16 at%Al alloy was investigated,focusing on both, phase stability and ageing behavior of martensite as afunction of alloy composition. To provide insights into these attributes, anexhaustive analysis of transformation temperatures and martensite stabilizationwas carried out, using electrical resistance measurements, tensile testing andmicrostructural examination across a range of Ni concentrations. Findingsrevealed a linear correlation between alloy composition and the martensitictransformation temperature, facilitating a refinement of existing predictivemodels. Additionally, the activation energy for martensite stabilization (Ea) was also determined as afunction of Ni concentration. A linear relationship between Ea and the composition of the alloy wasdetermined to be the best correlation according to the observed behavior. Finally,the L21 antiphase domain boundaries were analyzed,showing a reduction in domain size with increasing Ni content.