Papers by Keyword: Equilibrium Solubility

Abstract: The effects of Co on the strength of Cu-Ni-Co-Si alloys have been investigated using Cu-2.0wt%Ni-0.5wt%Si (0%Co), Cu-1.4wt%Ni-0.6wt%Co-0.5wt%Si (0.6%Co) and Cu-1.0wt% Ni-1.0wt%Co-0.5wt%Si (1.0%Co) alloys produced by combining cold rolling to a 25% reduction with aging. Aging the 0.6%Co and 1.0%Co alloys at 525 and 425°C produces orthorhombic (Ni, Co)₂Si precipitates that have the same crystal system as Ni₂Si precipitates formed in the 0%Co alloy. The larger the amount of Co in the three alloys is, the higher the strength and electrical conductivity of the alloys initially aged at 525°C, rolled to a 25% reduction and re-aged at 425°C become. The increase in strength with increasing Co content is caused by both of the decrease in inter-precipitate spacing and increase in dislocation density. The increase in strength by re-aging at 425°C becomes more pronounced as the Co content increases. This arises because the larger the amount of Co is, the larger the difference between the equilibrium solubilities at 525 and 425°C becomes, the more the volume fraction of precipitates is increased by re-aging at 425°C.