| The Cu-Cr-Ti alloy prepared by the directional solidification method can exert both the high conductivity of the copper matrix and the strengthening effect of the fibrous second phase,which has a broad market prospect.However,with the rapid development of electrification roads,the higher requirements have been put forward for contact lines and lead frame materials,therefore,it is very necessary to develop the new high-performance copper alloy.This paper is based on the above background,Cu-Cr-Ti alloys were prepared by the liquid metal cooling(LMC)method at high directional solidification rate.Then studies the effects of directional solidification rate and the different content of Cr and Ti elements on microstructure and properties.The paper explored the heat treatment process and aging precipitation behavior of thermomechanical treatment directional solidified Cu-Cr-Ti alloy,and compared with the microstructure and properties of "cast-extrusion" Cu-Cr-Ti alloy with the same deformation heat treatment process.It revaled that the high-temperature anti-softening mechanism of CuCr-Ti alloy prepared by two methods.A complete structure-activity relationship is formed between the craftsmanship-composition-structure-property of the directional solidification CuCr-Ti alloy in this paper,the following conclusions were obtained:For the directional solidification Cu-Cr-Ti as-cast alloy,as the directional solidification rate increases,the ?-Cu phase will undergo interface instability and morphological transformation: Flat interface ? Cell crystals ? Cell dendrites ? Columnar dendrites ? Columnar crystals,the critical transition rates of flat / cell and cell / branch are about 10 ?m/s and 30 ?m/s in Cu-0.3 alloy;Cr element exists in the form of granular ?-Cr phase,and its axial size will increase as the directional solidification rate increases;The Ti element is dispersed in the matrix as solid solution atoms and will refine the ?-Cu phase grains,and hinder the axial growth of the ?-Cr phase;The hardness of the directional solidified Cu-Cr-Ti as-cast alloy sample is about 20 HV higher than that of the "casting-extrusion" sample,and the conductivity is not much different;Directional solidified Cu-0.3Cr and Cu-0.67 Cr as-cast alloys reach the peak performance value of 63 %IACS?13.5 HV and 47% IACS?128.2 HV,respectively;The directional solidification Cu-0.31Cr-0.18 Ti alloy has a 20% increase in hardness compared to the Cu-0.3Cr alloy,and the electrical conductivity has decreased by 38.4%.For the thermomechanical treatment directionally solidified Cu-Cr-Ti alloy,it will seprates out the nano-scale ??-Cr phases and ??-Cu4 Ti ordered phase during the aging process,and ??-Cu4 Ti ordered phase will significantly inhibit the size of the precipitated ??-Cr phase;The directional solidification Cu-0.3Cr and Cu-0.67 Cr alloys in the as-pulled state after aging at 450 ° C?1 h and 400 ° C ?1.5 h respectively,their comprehensive properties reached a peak of 86.5 % IACS,548.7 MPa and 70.2 % IACS,589.9 MPa;The Cu-0.33Cr-0.05 Ti and Cu-0.31Cr-0.18 Ti alloy samples at different directional solidification rates have an electrical conductivity of about 80 % IACS and 70 % IACS after aging,and the peak tensile strength reaches 589.5 MPa,623.5 MPa;The high temperature anti-softening temperature of Cu-Cr-Ti alloy peak-aged samples prepared by directional solidification method and "casting + extrusion" method are 590 ? and 560 ?,respectively,and the high temperature softening of the alloys prepared by two methods is caused by static reply,precipitation Cr phase coarsening,static recrystallization and recrystallized grain growth at different annealing temperatures. |
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