| Cu-Cr based alloys are widely used in the fields of electrical contact wires,electrode materials and integrated circuit lead frames because of high strength and high conductivity.However,the traditional Cu-Cr binary alloy has obvious disadvantages,such as poor thermal stability,low recrystallization temperature and poor softening resistance.In order to improve the properties of Cu-Cr alloys,the effects of Y on the microstructure,mechanical properties and softening resistance of Cu-Cr alloy were systematically studied in this paper.In this study,Y(0wt.%,0.05 wt.%,0.10 wt.%,0.15 wt.%)were added to Cu-0.36 Cr,Cu-0.9Cr and Cu-1.45 Cr alloys,respectively,Cu-x Cr-y Y ingots were prepared by vacuum melting method,and the microstructure and properties of as-cast alloys were analyzed.Then,the ingots were treated with "Solid solution and aging(SSA)" and "Cold rolling and aging(CRA)",respectively.The effects of aging process and Y content on the microstructure and properties of the aged alloys were discussed,and the softening temperature of cold-rolling peak aging alloys was evaluated.Finally,Zr was added to the Cu-0.36Cr-0.05 Y alloy and the effect of processing technology on the microstructure and properties of the Cu-Cr-Y-Zr alloy were studied.The conclusions of research are as follows:1.By studying the microstructure and property of as-cast alloys,it is found that,without the addition of Y,the Cu-0.9Cr alloy is the alloy with the most equiaxed grains,the smallest grains and the highest hardness among the three alloys.After adding Y to the alloys,the microstructure of Cu-0.36 Cr alloy has no obvious change,and the eutectic microstructure is refined and more dispersed in the Cu-0.9Cr and Cu-1.45 Cr alloys.When 0.05 Y is added to Cu-0.36 Cr,Cu-0.9Cr and Cu-1.45 Cr alloys,the hardness of the alloys was improved.2.The solid solution and cold-rolled samples were aged at 460℃ respectively,and the effects of aging process and rare earth Y on the properties of the alloy were studied.CRA process can improve mechanical properties of aged alloys,the hardness(155-160 HV)and tensile strength(460-480 MPa)of CR peak-aged Cu-x Cr-y Y alloys are significantly better than those of peak-aged SSA alloys(<140 HV,<330 MPa).The addition of Y improves the peak-aged hardness and conductivity of CRA alloys.Adding 0.05 Y to Cu-0.36 Cr alloy,and adding 0.1Y to Cu-0.9Cr and Cu-1.45 Cr alloys can make alloys obtain the best matching between strength and conductivity,which were 485MPa/86.1%IACS,465MPa/87.12%IACS and 466MPa/87.09%IACS,respectively.3.Rare earth Y significantly improves the over-aging resistance of cold-rolled Cu-Cr alloys.After CRA/300 min,the tensile strength(423MPa)of Cu-0.95Cr-0.1Y alloy are obviously better than that of Cu-0.9Cr alloy(330MPa),which is attributed to the fact that rare earth Y inhibits the coarsening of the Cr during the aging process,delays the recrystallization process and retains higher dislocation density.In addition,Y increases the softening temperature of CR peak-aged alloys by ～70℃,because Y inhibits the diffusion of Cr and coarsening of precipitates during aging,hinders the transformation of Cr precipitates with F.C.C structure to B.C.C and retains the precipitation strengthening effect.4.After adding 0.08 Zr to Cu-0.36Cr-0.06 Y alloy,the hardness of the alloy as cast,rolled and CRA was improved The two-stage cold rolling and aging process of "Solution-Rolling-Aging-Rolling-Aging" can improve the alloy strength and the electrical conductivity.The Cu-Cr-(Zr)alloy containing Y element has good comprehensive properties with tensile strength 535 MPa and conductivity 83.79%IACS,respectively,which were39 MPa and 2.92%IACS higher than those of the peak-aging CRA alloy,respectively. |
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