In order to investigate the effect of Hf-content on phase transformation behavior and the microstructures of Ti-Ni-Hf shape memory alloys, differential scanning calorimetry, X-ray diffraction and transmission electron microscopy were performed. The on...
In order to investigate the effect of Hf-content on phase transformation behavior and the microstructures of Ti-Ni-Hf shape memory alloys, differential scanning calorimetry, X-ray diffraction and transmission electron microscopy were performed. The one stage B2(cubic)-B19'(monoclinic) transformation occurred in the alloys whose Hf-contents are less than 10 at%, while both the B19(orthorhombic) and the B19' martensite coexisted in the alloys whose Hf-content is more than 10 at%, indicating that the B2-B19 and the B19-B19' transformations were not separated. Transformation temperatures decreased with increasing the Hf-content for the alloys whose Hf-contents are less than 5 at%, and then increased for those whose Hf-content is more than 5 at% and less than 15 at%. Further increasing Hf-content, however, the decrease in transformation temperatures which may be attributed to an unknown phase was observed. The (001) twin as an internal defect existed in the B19' martensite, while did not exist in the B19 martensite.