| Research Abstract |
The relation between the phase stability and high-temperature strength has been investigated for the pseudobinary (FeィイD21-xィエD2MィイD2xィエD2)ィイD23ィエD2Al alloys with addition of transition metals M = Ti, V, Cr, Mn and Mo. The substitution of these transition elements results in a remarkable stabilization of the D0ィイD23ィエD2 phase, as proved by an increase in the long-range order parameter and also a coarsening of the D0ィイD23ィエD2 antiphase domains. The rapid increase in the D0ィイD23ィエD2-B2 transformation temperature, ΤィイD2cィエD2, determined from electrical resistivity measurements, can be explained by the electron concentration effect due to the site preference of the substituted atoms. Vickers microhardness measurements show that the present pseudobinary alloys exhibit a significant improvement in the high-temperature strength up to 1000Κand above. Moreover, according to compression tests, a slight substitution of V and Mo induces a sharp decrease in the room-temperature yield stress. Further addition induces an increase in the yield stress due to solid-solution strengthening for Μ = V : precipitation strengthening can also be found for Μ = Mo. As the temperature is raised above 600Κ, the yield stress increases and exhibits a peak at higher temperatures with increasing ΤィイD2cィエD2 by the V and Mo substitution. It is also found that the strain rate sensitivity rises sharply when the peak temperature is reached, whilst it is near zero at lower temperatures. We conclude that, for Μ = V and Mo, the peak temperature varies with the increase ΤィイD2cィエD2, which supports a direct correlation between the loss of D0ィイD23ィエD2 order and the anomalous increase in yield stress.
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