Effects of grain orientation and precipitates on the superelasticity in directionally solidified FeNiCoAlTaB shape memory alloy

FeNiCoAlTaB alloy with good superelasticity was fabricated by using the directional solidification technology to control grain orientation and solution-aging treatment to change the morphology and distribution of precipitates, and the superelasticity improving mechanism of the alloy was investigated in this study. The results indicated that with the melt zone temperature of 1420 +/- 5 degrees C and withdrawing velocity of 0.5 mm/min, the columnar-grained FeNiCoAlTaB alloy with strong < 100 > fiber texture was obtained. After solution treatment at 1315 degrees C for 20 min and aging at 700 degrees C for 6 h, the columnar-grained FeNiCoAlTaB alloy exhibited the superelasticity strain of 1.7%, residual strain of 0.5% and tensile strength of 860 MPa. Compared with the non-superelastic equiaxed-grained alloy fabricated by vacuum melting and forging, the desired grain orientation, the size and distribution of the precipitates resulted in the good superelasticity of the columnar-grained FeNiCoAlTaB alloy. (C) 2016 Elsevier B.V. All rights reserved.