Effect of thermomechanical processing on the age-hardening and contraction behavior of Cu-Be alloys with Co and Ni

摘要

Cu-Be alloys are extremely hardened byaging at 523-673K after quenching from solutiontreatment temperatures (1073-1093K). The hardeningis caused by the formation of G.P. zone, γ" phaseand γ' phase (CuBe'). Commercial Cu-Be alloys,which are mainly used for electronic devices, areadded small amounts of Co and Ni elements in orderto improve mechanical properties.By the addition of these elements, fine insolubleparticles such as BeCo and BeNi are dispersed inthe matrix and grain boundaries. These fineparticles suppress the recrystallization and graingrowth during solution-treatment after heavy coldworking (~90% cold rolling), andalso suppress theprogress of discontinuous precipitation (cellularprecipitation) on the subsequent aging. As aresult, mechanical properties and heat resistanceof the alloy increase. However, these fineparticles cause oriented structure (annealingtexture) in an as-quenched sheet, resulting inanisotropic contraction of the sheet on the subsequent aging.In this study, the effectof thermomchanicalprocessing on the improvement of anisotropy in theaged sheets between the contraction in the rollingdirection and that in the transverse direction wasexamined. It became clear that a suitable working(20~50% of cold rolling) before aging promoted thehardening in the matrix on the subsequent agingand could prevent the anisotropic contraction ofthe sheet. The mechanism was discussed.