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The oxidation behavior of Ti 5 Si 3 has been studied in air in the temperature range of 1200 ЊC to 1400 ЊC. The oxidation kinetics is slower than that predicted by the parabolic-rate law equation at 1200 ЊC, but is sharply enhanced beyond a temperature of 1300 ЊC. The oxidation kinetics of a Ti 5 Si 3 -8 wt pct Al alloy and a Ti 5 Si 3 -20 vol pct TiC composite at 1200 ЊC has also been investigated and compared to that of Ti 5 Si 3 . Alloying with Al does not alter the oxidation resistance much, but the presence of TiC reinforcements enhances the rate of oxidation significantly. The oxidation products have been identified and the mechanism of oxidation has been analyzed using thermodynamic and kinetic considerations.

The microstructure and phase stability of the Fe-15Mn-7Si-9Cr-5Ni stainless steel shape memory alloy in the temperature range of 600 °C to 1200 °C was investigated using optical and transmission electron microscopy, X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and chemical analysis techniques. The microstructural studies show that an austenite single-phase field exists in the temperature range of 1000 °C to 1100 °C, above 1100 °C, there exists a three-phase field consisting of austenite, d-ferrite, and the (Fe,Mn) 3 Si intermetallic phase; within the temperature range of 700 °C to 1000 °C, a two-phase field consisting of austenite and the Fe 5 Ni 3 Si 2 type intermetallic phase exists; and below 700 °C, there exists a single austenite phase field. Apart from these equilibrium phases, the austenite grains show the presence of athermal martensite. The athermal aЈ martensite has also been observed for the first time in these stainless steel shape memory alloys and is produced through the ␥--␣Ј transformation sequence.

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