Cu-Be合金の時効硬化におよぼす各種低融点元素添加の影響

Abstract

It seems possible that additions of small amounts of several common low-melting-point elements around indium in the periodic table may have some significant effects on age-hardening of Cu-Be alloys, since the previous work has shown that the addition of indium has a pronounced influence on the response of Cu-Be to aging. Experiments have been performed using samples of Cu-1.6%Be ternary alloys with less than 1% of phosphorus, zinc, arsenic, cadmium, tin, antimony or lead to investigate the effect of each element on the age-hardening curves and aged microstructures after solution treatment at 800°C and 50% reduction by cold-rolling. The addition of phosphorus or arsenic promotes greatly the discontinuous precipitation and over-aged softening. Zinc also acts in the same way but much less. A small amount of lead has no significant effect. Contrary to these, the addition of cadmium, tin or antimony supresses the discontinuous precipitation, making the alloy more insensitive to over-aging and improving the mechanical properties. In case the amount of cadmium, tin or antimony is about 0.13 at%, the activation energy obtained from aging curves decreases to the range of 13 to 15 kcal/mol which is fairly lower than that obtained in Cu-Be binary alloy by the same method. The reason of this may be explained by the facilitation of nucleation as in the case of indium addition. Examined elements, indium, cadmium, tin and antimony, which have been verified to improve the aging properties of Cu-Be, have larger atomic sizes than copper. Their size-factors for copper are at the borderline or slightly unfavourable.