Combustion synthesis/quasi-isostatic pressing of TiC0.7–NiTi cermets: microstructure and transformation characteristics
- 126 Downloads
TiC0.7–NiTi cermets were produced by combustion synthesis followed by quasi-isostatic consolidation while the reaction products were still hot and ductile. The TiC0.7–NiTi cermets were characterized by differential scanning calorimetry, room temperature transmission electron microscopy (TEM), and in-situ TEM (temperature varied during observation). The matrix of the as-synthesized 20NiTi, 40NiTi, and 60NiTi composites contains both R and B19′ martensites at room temperature. No distinct R-phase morphology could be imaged. In the B19′ martensite,  Type II twinning, \( (11\bar 1) \) Type I twinning and (001) compound twinning modes were observed as the lattice invariant shear (LIS) of the R-B19′ transformation. The  Type II twinning is often reported as the LIS of the B2-B19′ transformation, but this is the first experimental confirmation of its predicted presence as a qualified LIS of the R-B19′ transformation. The (001) compound twinning mode is responsible for the fine structure of the martensite with a wavy morphology. Nanoscale structures with a thickness of 5 nm were obtained inside the twins. Twinning was also observed at the interface with carbide particles, which confirms that some stress relaxation of the elastic mismatch occurs. At room temperature, the matrix of the 80NiTi composite had the R-phase structure, which appeared with a needle-like morphology. Thermal cycling resulted in the suppression of the R-phase transformation. This is the opposite of the behavior observed in un-reinforced NiTi alloys.
KeywordsMartensite Differential Scanning Calorimetry Curve Carbide Particle Dark Field Image Select Area Diffraction Pattern
This research was supported by the Director, Office of Science, Office of Basic Energy Sciences of the US Department of Energy under contract No. DE-AC03-76SF00098.
- 1.Merzhanov AG, Borovinskaya IP (1972) Dokl Akad Nauk SSSR 204:336Google Scholar
- 2.Gordopolov Y, Merzhanov A (1993) AIAA 154:539Google Scholar
- 3.Shikhverdiev RM, Yu A (1992) Intl J SHS 1:64Google Scholar
- 6.Strutt ER, Olevsky EA, Meyers MA (2008) Paper 1: Combustion synthesis/quasi-isostatic pressing of TiC–NiTi cermets: processing and shrinkage anisotropy (in press)Google Scholar
- 12.Miyazaki S, Otsuka K, Wayman CM (1989) Acta Metall 37:1837Google Scholar
- 21.Stroz D (1997) J Phys IV C5:C5–293Google Scholar
- 24.Honma T (1987) In: Funakubo H (ed) Shape memory alloys. Gordon and Breach, New York, NYGoogle Scholar
- 25.Hanlon JE, Butler SR, Wasilewski RJ (1967) Trans Met Soc AIME 239:1323Google Scholar
- 26.Todoroki T (1990) In: Duerig TW (ed) Engineering aspects of shape memory alloys, Butterworth and Co., London, p 315Google Scholar