Abstract: Fe_42.5Ni₂₈Co₁₇Al_11.5Ta₁ (at.%) alloy was aging treated at different temperatures. Microstructure observation and phase analysis of the aged alloy were carried out by scanning electron microscopy and X-ray diffractometer, and the lattice parameters were determined through Origin Peak Fit Module software. Meanwhile, the hardness and pseudoelasticity of the alloy aged at different temperatures were measured at room temperature. The results show that, the precipitates in the grain interior change from γ′ phase to γ′ and β phases when the aging temperature increases from 600 ℃ to 650 ℃ and 750 ℃ with 60 h aging time maintained. The precipitation of β phase is related to the increase of solid solubility of Ta element in the matrix at higher aging temperature. In the single-phase precipitation mode, the alloy exhibits pseudoelasticity at room temperature, with a recoverable strain of 10.01%. However, in the two-phase precipitation mode, the alloy exhibits superelasticity at room temperature, with a small stress hysteresis and a recoverable strain of 12.41%. After aging at 650 ℃, the alloy exhibits the best pseudoelasticity at room temperature.

Key words: shape memory alloy, aging, pseudoelasticity, Fe-Ni-Co-Al-Ta, martensitic transformation