Microstructural evolution and mechanical properties of Ni-45Ti-5Al-2Nb-1Mo alloy subjected to different heat treatments

The effects of solution and aging heat treatment on microstructural evolution and room temperature tensile properties for as-forged Ni-45Ti-5Al-2Nb-1Mo alloy were investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tensile tests. The results show that the microstructure of solution-treated alloy comprises NiTi matrix, Ti2Ni and (Nb,Ti)(SS) phases. After aging treatment at 700 & DEG;C for 6 and 100 h, the distribution of Ti2Ni and (Nb,Ti)(SS) precipitates increases in uniformity. No new type of precipitate is observed in the specimen aged at 700 & DEG;C. After aging at 800 & DEG;C for 100 h, numerous nanosized Ni2TiAl phases are precipitated within the grains. Solution and aging treatments improve the tensile properties at room temperature. Tensile strength and ductility are improved after solution treatment at 1100 & DEG;C plus aging treatment at 800 & DEG;C for 6 h or 700 & DEG;C for 100 h. With aging time prolonging to 100 h at 800 & DEG;C, the precipitation of fine Ni2TiAl particles leads to the improvement in tensile strength and deterioration of elongation.

Automated summary

The impact of solution and aging heat treatment on microstructural evolution and room temperature tensile properties for as-forged Ni-45Ti-5Al-2Nb-1Mo alloy was studied. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and tensile tests were used. The results showed that the microstructure of the solution-treated alloy consisted of NiTi matrix, Ti2Ni, and (Nb,Ti)(SS) phases. Aging treatment at 700°C for 6 and 100 hours increased the uniformity of Ti2Ni and (Nb,Ti)(SS) precipitates. Aging at 800°C for 100 hours resulted in the precipitation of nanosized Ni2TiAl phases within the grains, significantly improving tensile strength but reducing elongation.