The hardness of materials, H, is dependent on grain diameter, d, in a similar way as the flow stress in the Hall‐Petch relation: H = Ho + KHd−1/2, where, Ho and KH are constants. The microhardness of 2S‐Al (99.5% Al), pure Cu, Al‐MD 105 (Al‐1% Al2O3), and Duralumin (Al‐3.94% Cu) is found to vary with grain size according to the Hall‐Petch equation with reasonable accuracy. The grain boundary hardening KH of Al‐MD 105 is found to be the highest although this material recrystallizes to larger grain sizes than those for the other materials; this is attributed to the resistance of boundaries to deformation arising mainly from the presence of hard, second phase alumina particles. However, the contribution of solution, precipitation, and dispersion hardening may be added to grain boundary hardening according to Hansen and Lilholt.

No abstract

No abstract

As-Se-Cu glasses, with Cu content varying between 5 and 25 at. %, were produced by quenching from the melt. The values of resistivity and activation energy for conduction decreased continuously with increasing the copper content. Memory switching phenomena was observed in glasses containing Cu less than 20 at. %. Glasses containing higher Cu concentration showed a reverse switching cycle. Thermally induced changes in the structural properties have been examined using x-ray diffraction, differential thermal analysis, and scanning electron microscopy. The results were discussed on the basis of thermally induced transformations.

No abstract