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Generally, a B2–B19 one-stage phase transformation exists in Ti50PdxNi50−x alloys when Pd content is higher than 20 at.%. However, in Ti rich Ti50+xPd30Ni20−x alloys, a B2–B19–B19′ two-stage transformation can also take place. The alloys were firstly heated to high temperature of solid solutions, and then the one-stage transformation can be retained by subsequent furnace-cooling as well as the two-stage transformation by quenching. Annealing at lower temperature does not change the nature of the phase transformations. Differential scanning calorimetry (DSC), X-ray diffractometry (XRD), dynamic mechanical thermal analysis (DMTA) and transmission electron microscopy (TEM) were used to ascertain the characteristics of the phase transformations. Discrepancies between the transformation elastic modulus of B2-B19 and B19-B19′ have been found, a trough and a step can be employed for a description, respectively. The damping properties of the materials were also investigated, all the results provide valuable information for designs of intelligent materials and structures aimed for vibration control. [ABSTRACT FROM AUTHOR]

Abstract: Pest oxidation and oxidation kinetics of MoSi2 at 773K were investigated and compared using as-cast, spark plasma sintered poly-crystalline MoSi2 and MoSi2 single crystal. Specimens (either poly- or single-crystalline) containing cracks are liable to pest disintegration after a certain period of exposure. High temperature in situ observation shows that new cracks tend to nucleate at the pre-existing cracks'' tip but not at grain boundary or porosity. The MoSi2 single crystal shows a much lower weight gain compared to the dense poly-crystal during a 300h exposure. The oxidation kinetics changes from a linear law for the poly-crystalline specimen to a parabolic-like law for the single crystal. A protective compact oxide scale is formed on the MoSi2 single crystal. However, the oxide scale formed on the poly-crystalline specimen is porous and full of cracks. This difference is discussed in the light of different diffusion rates in the bulk matrix and at the grain boundary. [Copyright &y& Elsevier]

Abstract: Effect of Mo addition on phase stability of β-Nb5Si3 in NbSi2/Nb5Si3 in situ composites has been investigated using X-ray diffraction (XRD). The preferential occupancy of the Mo atoms in the β-Nb5Si3 structure was investigated with the Rietveld profile technique. It is suggested that Mo addition stabilizes the β-Nb5Si3 phase. The results were explained on the basis of selective substitution of Mo atoms in β-Nb5Si3. [Copyright &y& Elsevier]