Effects of Quenching Methods on Martensite Transformation and Shape Memory Effects of Cu-27.66Al-12.39Mn Alloy

Shape Memory Alloys (SMAs) exhibit unique functional properties associated with reversible martensitic transformation. This study investigates quenching methods on the microstructure and properties of Cu-27.66Al-12.39Mn (at.%) alloy. The alloy was fabricated by gravity casting, homogenized at 900 °C for 2 h with air cooling, and subsequently betatized at 900 °C for 30 min followed by three quenching routes: direct quenching (DQ), up quenching (UQ), and step quenching (SQ) The microstructure evolution of betatized sample was characterized by x-ray diffraction, optical and scanning electron microscope. The mechanical properties were evaluated by hardness and semi-empirical bending test. The alloy exhibited a β1 (L21) microstructure in both as-cast and as-homogenized conditions, with grain growth observed. The quenching method significantly effects on microstructure and hardness of Cu-Al-Mn alloy. All quenching method resulted in partial formation βʹ1 (18R) martensite with thin plate morphology. The hardness values of DQ, UQ, and SQ samples were 366.71, 359.61, and 347.74 HVN, respectively, relating with the inverse relationship with grain size. The martensitic transformation temperature expected on cryogenic temperature (< -60 °C), so the strain recovery test at room temperature failed.