Effect of solidification conditions on microstructure, hardness, and transformation behavior of a Cu–Al–Mn shape memory alloy produced by centrifugal casting

The effect of solidification conditions on the microstructure, transformation behavior, and hardness of a Cu–8.41Al–11.25Mn (wt.%) shape memory alloy was investigated using centrifugal casting. Different cooling conditions were achieved through a stepped copper mold. Microstructure, phase constitution, transformation behavior, and mechanical response were characterized by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, and Vickers microhardness testing, supported by CALPHAD thermodynamic calculations. The smaller-diameter samples, associated with faster solidification conditions, exhibited a refined microstructure and XRD features consistent with a higher fraction of 18 R and 2H martensites. Despite these changes, the austenitic and martensitic transformation temperatures remained essentially unchanged, whereas the thermodynamic equilibrium temperature (T 0 ) decreased progressively with increasing cooling rate. Higher cooling rates also led to lower hardness, primarily due to the greater fraction of martensite in the microstructure. These findings demonstrate that, within the range of solidification conditions investigated, the cooling rate has a pronounced effect on microstructural refinement, phase constitution, and T 0 , while exerting only a negligible influence on the transformation temperatures.