Effects of the addition of boron on grain boundary precipitation, martensitic transformation temperatures, and mechanical properties were investigated for Fe-31.9Ni-9.6Co-4.7Ti alloy sheets. Grain boundary precipitation of the η-Ni3Ti phase with the D024 structure, which significantly deteriorates the mechanical properties, is effectively suppressed by the addition of a small amount of B. Both the transformation temperature and the thermal hysteresis slightly increase with increasing B composition. Tensile fracture elongation is improved to be about 1.3 % by addition of 0.05 % B, but no superelastic property was detected in the cyclic stress–strain curve. The features in the mechanical properties are discussed with the texture properties in the sheet specimen.
- Grain boundary precipitation
- Mechanical behavior