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A new process concept, "quenching and partitioning" (Q&P) has been proposed recently for creating steel microstructures with retained austenite. The process involves quenching austenite below the martensitestart temperature, followed by a partitioning treatment to enrich the remaining austenite with carbon, thereby stabilizing it to room temperature. The process concept is reviewed here, along with the thermodynamic basis for the partitioning treatment, and a model for designing some of the relevant processing temperatures. These concepts are applied to silicon-containing steels that are currently being examined for low-carbon TRIP sheet steel applications, and medium-carbon bar steel applications, along with a silicon-containing ductile cast iron. Highlights of recent experimental studies on these materials are also presented, that indicate unique and attractive microstructure/property combinations may be obtained via Q&P. This work is being carried out through a collaborative arrangement sponsored by the NSF in the USA, CNPq in Brazil, and the EPSRC in the United Kingdom.

The Pbcn orthorhombic phase of Y 2 Mo 3 O 12 has been examined through high-resolution X-ray powder diffraction (10-450 K), heat capacity determination (2-390 K), and differential scanning calorimetry (103-673 K). No phase transition was found over this temperature range. The overall thermal expansion is negative, and the average linear thermal expansion coefficient, R l , is -9.02 Â 10 -6 K -1 averaged over T = 20-450 K. From a thorough analysis of the structure of Y 2 Mo 3 O 12 , we find that the YO 6 octahedra and MoO 4 tetrahedra are increasingly distorted with increasing temperature. The inherent volume distortion parameter (υ) of AO 6 has been introduced to quantitatively evaluate polyhedral distortion and it is observed that this parameter is strongly correlated with the linear coefficient thermal expansion (R l ) of different members of the A 2 M 3 O 12 family. We attribute the negative thermal expansion to the reduction of the mean Y-Mo nonbonded distances and Y-O-Mo bond angles with increasing temperature, the joint action of high-energy optical and low-energy translational and librational modes.

H-trititanate nanotubes obtained by alkali hydrothermal treatment of TiO(2) followed by proton exchange were compared to their bulk H(2)Ti(3)O(7) counterpart with respect to their thermally induced structural transformation paths. As-synthesized and heat-treated samples were characterized by XRD, TEM/SAED, DSC and spectroscopy techniques, indicating that H(2)Ti(3)O(7) nanotubes showed the same sequence of structural transformations as their bulk counterpart obtained by conventional solid state reaction. Nanostructured H(2)Ti(3)O(7) converts into TiO(2)(B) via multistep transformation without losing its nanotubular morphology. The transformation occurs between 120 and 400 degrees C through topotactic mechanisms with the intermediate formation of nanostructured H(2)Ti(6)O(13) and H(2)Ti(12)O(25), which are more condensed layered titanates eventually rearranging to TiO(2)(B). Our results suggest that the intermediate tunnel structure H(2)Ti(12)O(25) is the final layered intermediate phase, on which TiO(2)(B) nucleates and grows. The conversion of nanostructured TiO(2)(B) into anatase is completed at a much lower temperature than its bulk counterpart and is accompanied by loss of the nanotubular morphology.