Cu-cr Alloy, The Precipitation Mechanisms And Theoretical Research

Cu-Cr alloy is the typical aging hardening alloy, from the study of the microcosmic mechanism, we can find the rule which would be beneficial to the design for Cu alloy.The valence electron structures of main phases and phase inter-phase boundaries in Cu-Cr binary alloy were analyzed according to the Empirical Electronic Theory in solid and molecules (EET). The following aspects are included in this thesis:1. We drew curves of changes of micro-hardness with aging times at different temperature, aging curves of changes of conductivity with aging times at different temperature in different contents for Cu-Cr alloys, and dynamics curves of Cu-Cr alloys at different aging temperature. Based on the calculation, we chose Cu-0.48Cr alloys and did HRTEM observe to identify the deposit sequence, opposite precipitates and orientation relationship between the matrix and precipitates Cr, to provide experiment proof for the followed calculation of the valence electron structures of main phases and phase inter-phase boundaries in Cu-Cr binary alloy2. The models of valence electron structure of main phases in Cu-Cr binary alloy were established. The solid solution of Cu-Cr binary alloy was contained two cells: matrix Cu cell, Cu-Cr cell. The valence electron structures of above cells were calculated.3. The valence electron structures of the precipitations of Cu-Cr binary alloy in early aging, such as phase of G.P zone and Cr precipitates were calculated.4. The valence interface energy of phase inter-phase boundaries between the matrix and the phase of G.P zone were calculated. The formation of precipitates Cr is interpreter according to the valence electron structures.5. The valence electron structures of phase interface boundary between the matrix and the precipitation are calculated.6. The inter-phase integrate gene and phase integrate gene were calculated and strengthening mechanisms in Cu-Cr alloy are investigated on the valence electron structure lever.The results show that:The deposit sequence and opposite precipitates were identified as: at low temperature: Cu solid solution→Cr G.P zone→coherent Cr phase (b.c.c) →incoherent Cr phase (b.c.c) ; at high temperature: Cu solid solution→coherent Cr phase (b.c.c) →incoherent Cr phase (b.c.c) .The strong interaction of Cu with Cr in solid solution of Cu-Cr alloy, which lead to the behavior of Cu-Cr segregation. The strong segregations are restrained the growth of the matrix and the strengthening of the alloy was promoted.The strongest bond Cu-Cr bond in super-saturation solid solution of alloy is lower than the one in the matrix contribute to the low heat stability which lead to the decompose, accordingly the new phase segregate from the super-saturation solid solution.The bond net of the strongest and the hypo-bond in the cell of precipitate Cr which formed difficult to cut in the aging process, are so strong that the dislocation is so the strength is improved.The inter-phase energy between the phase (111) of matrix Cu and the phase (001) of G.P zone is small, which account for the reason why the interface matched so well that the interface is more stable. The matrix Cu and precipitate Cr match well, the surface energy of the precipitates Cr (110) is higher than the one of matrix Cu (111), which lead to the adsorption of the precipitates is stronger than the one of matrix.On the inter-phase boundaries between the matrix and the G.P zone, electronic density is continued, The functions of aging hardening are remarkable, however, on the inter-phase boundaries between the matrix and precipitates Cr, the electronic density is continued, The functions of aging hardening is up to highest micro-hardness.