Effect of prior deformation on dimensional change and precipitation process in a Cu-1.8wt%Be-0.2wt%Co alloy aged at 320°C

金沢大学理工研究域機械工学系
The influence of prior cold work (90% reduction) on the length change and precipitation behaviour of a Cu-1.8wt%Be-0.2wt%Co alloy aged at 320C up to 350 h has been investigated. The alloy gradually expands to a maximum and then contracts during ageing. The maximum expansion is attributable to both the expansion due to the loss of Be solute atoms and the contraction due to precipitation of the [image omitted], I, m and ' phases. The subsequent contraction results from the decrease in amounts of the [image omitted] and m phases and the increase in amount of the ' phase. The new-found m phase, consisting of alternate Be and Cu matrix layers parallel to the matrix {001}, is body-centred monoclinic with a = b = 0.263 nm and c = 0.279 nm and = 83, and aligns with the matrix according to the Bain orientation relationship. The Guinier-Preston (GP) zone transforms continuously to the m or I phase via '' and [image omitted]. The transformation from the GP zone to ' via '', [image omitted] and I is retarded in comparison with that for the un-deformed alloy.全文公開201002