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Copper and copper-base alloys are used widely because they have the advantages of high electrical and thermal conductivities, good mechanical properties, outstanding corrosion and fatigue resistance,and ease of fabrication. However, comprehensive properties are more and more required for copper alloys with the rapid development of the electronic industry. For example,a tensile strength σ_b> 600 MPa , hardness Hv> 180 and conductivity >80%IACS are demanded for lead frame materials on a very large scale integrated circuit. It is necessary to study the copper-based alloys of higth strength and excellent conductivity.Cu-0.8Cr-0.05Y and Cu-0.8Cr-0.05Nd alloys were prepared by vacuum median frequency smelting. Two kind processing crafts to the casting Cu-0.8Cr-0.05Y and Cu-0.8Cr-0.05Nd alloys: processing A is casting +cold working +aging, and processing B is casting + solution treated + cold working + aging. Using electrical resistance test, hardness measurement, tensile test , softing temperature , optical microscopy , XRD , SEM and TEM , the electric properties and the mechanical and the microstructure of the alloys at different treatment were studied. Them were also analysed and explained in theory. The results show that:The first, Cu-0.8Cr-0.05Y and Cu-0.8Cr-0.05Nd alloys are tipical aging strengthing alloy. The electrical and mechanical performance processed A of the alloy with 95% cold deformation aged at 480℃ for 30 min can reach 90.7~93.2%IACS conductivity, 490~525MP_a tensile strength, (535-545)±5℃ sofeing temperatureand 14.0-17.5% elongation, prior to the alloy of processed B.The second, the strengthening mechanisms of above alloys mainly include solution strengthening, strain-strengthing and aging strengthening. Thermomechanical treatment can increase alloys’ strength greatly. The alloy in aging after cold-working was influenced by the interaction of precipitation and recrystallization, especia the alloy with heavy cold working. The precipitation can increase the hardness and electric conductivity of the tested alloy,but the recrystallization result in inefficient
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