CORRELATION OF THE THERMAL COMPONENT OF THE YIELD STRESS OF BODY CENTERED CUBIC METALS

Abstract : The variation of the thermal component of the yield stress, tau, with temperature for the Groups VA and VIA body centered cubic transition metals has been determined from data reported in the literature. It was found that the temperature dependence of tau is relatively in dependent of structure for a purity of < 99.98% by weight, but may decrease for higher purity material and for single crystals as compared to polycrystals, in agreement with what had previously been found for iron. By plotting tau versus the parameter (T-T sub zero)/T sub m, it was possible to correlate the data for all the b.c.c. transition metals. T is the test temperature, T sub zero the temperature where tau is first zero, and T sub m the melting temperature. The present results support thermally activated overcoming of the Peierls-Nabarro stress as the mechanism responsible for the strong temperature dependence of the yield stress in the b.c.c. metals.

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