Evaluation of Solubilization Time in Uncontrolled Atmosphere on Grain Growth, Phase Transformation Temperatures, and Mechanical Properties in a CuAlBe SMA
摘要
Thermomechanical properties of SMAs are strongly affected by the metallurgical conditions imposed during their production. In this work, experiments were performed to investigate the behavior of the Cu–11.8Al–0.50Be (wt pct) SMA during solubilization at different times under an uncontrolled atmosphere. The results presented serve as a basis for predicting the macrostructure and thermomechanical properties in practical applications using CuAlBe SMAs. The grain growth evaluated by OM proved to be extremely sensitive to treatment time even after short intervals, tending to stabilize after 12 hours. Chemical analysis by EDS indicated a small variation in Al content produced during solidification, with 3 hours being enough to homogenize the Al concentration throughout the ingot despite producing a microstructure with non-uniform grain size. This variation in Al is not significant enough to influence the phase transformation temperatures, with the changes attributed to the grain growth and loss of Be by oxidation. ¼ hour resulted in the lowest values for maximum stress/strain, while 24 hours of solubilization showed the highest values of strain with small dispersion. The mixed fracture type (brittle/ductile) observed by SEM in the ¼ hour samples supports the hypothesis that ¼ hour is insufficient to dissolve the phases formed during solidification. This effect is aggravated by the strong elastic anisotropy, which contributes to embrittlement during quenching.