Abstract
The addition of 0·1% P to an austenitic alloy containing 16% Cr, 16% Ni, and 0·25% C accelerated the precipitation of M23C6 on ageing in spite of the absence of marked structural changes in the precipitate distribution. An addition of 0·3% P to a 16% Cr 9% Ni 0·23% C alloy markedly accelerated precipitation, partly as a result of the farmation of matrix precipitation (MDP). The kinetic data obtained indicated that the diffusian rate of chromium is increased in the presence of phosphorus. Air-cooling after solution-treatment, as campared with water-quenching, promoted MDP formatian in both phosphorus-containing and phosphorus-free alloys; this is attributed to the farmation of complexes during the cooling. The MDP nucleated dislocation loops, which then grew and continued to nucleate M23C6. Thus, the rate of precipitation was similar after either water-quenching or air-cooling awing to the nucleated loops compensating for the initial lower dislocatian density of air-cooled alloys.