The hardness of primary solid solutions with special reference to alloys of silver

Accurate Meyer analyses have been made on annealed bars of vacuum-melted spectroscopically pure silver, assay silver, and on binary alloys of silver containing up to 5 atomic % of cadmium, indium, tin, antimony, zinc, aluminium, magnesium, and gold. The results show that in contradiction to the statements of some investigators, the ultimate Meyer hardness Pu increases as the grain size of the specimens diminishes. By means of suitable annealing treatments results were obtained for different grain sizes of alloys containing approximately 2·4 and 5·0 atomic % of the above elements, and these were used to deduce Pu values referring to one standard grain size. These values enable an accurate comparison of the relative hardening effects of the different solutes to be made. The results are discussed from the standpoint of lattice distortion, and it is shown that for a given atomic percentage of solute, the increase in Pu is proportional to the square of the lattice distortion for solutes in the same row pf the Periodic Table. No simple relation exists for solutes from different rows of the Periodic Table, and for a given solute the relation between Pu and the composition is not necessarily a simple one. The conclusions are tested by experiments on ternary alloys, and data for copper alloys are discussed.