Casting Cucr Alloy Microstructure And Properties

CuCr alloy has excellent physical and mechanical properties, so it can beextensively used as lead frame of integrated circuit, different electrodes, electriccontact and high strength conductor. It can also be used as wear-resistam materialsand in heat-exchange environment that has no direct relation with conductivity, so itcan be destined to have wide application prospect.In this paper, CuCr alloys with 0.l4%, 0.44%, l.28%, and 2.0% Cr content inweight were prepared by casting. The samples were electro-polished for microscopeobservation. Microstructure observation was carried out on the as-cast alloy andfurther processed alloy. The effects of Cr content and further process on theconductivity and mechanical properties were also studied, and finally the agehardening mechanism of CuCr alloy was analyzed by TEM observation. The resultsshowed that:l.The as-cast microstructure of hypoeutectic composition CuCr alloy was Curich phase and tiny eutectic colony a1ong the grain boundary The microstructure ofthe eutectic composition alloy was primary Cu rich dendrite and about 50%pseudoeutectic colony, while that of the hypereutectic composition alloy wasprimary Cr dendrite, Cu rich phase and eutectic colony under the condition of non-equilibrium solidification. After solution treatment and aging the outline of grainboundary of hyPoeutectic alloy disaPpeared while the bar shaPed eutectic Crparticles in the eutectic and hypereutectic alloys transformed into spherical orellipsoidal Cr pariicles.2. The conductivity of CuCr alloy was improved to a great extellt after solutiontreatInent and aging. Neither forging nor cold working process had effect on theconductivity.3.The tensile strength of CuCr alloy increased with the increase of Cr contentwithin the extent of l.28% in weight, and forging process could improve strengthsignificanly.4.Chromium content and fOrging process had little effect on the hardness ofCuCr alloy while Cr content was not more than 2.0% in weight. The hardness ofCuCr alloy would be enhanced extremely through aging treatInellt after so1utiontreatInent and cold working.5.The wear characteristics between CuCr alloy with Cr coniellt within 2.0% inweight and 45 steel belonged to adhesive wear. The al1oy with coarse eutectic andprimary Cr particles had higher wear-resistance than the hyPoeutectic alloy, and thealloy suffered forging had lower wear resistance while being wom in the direction offorging process.6.The Cr precipitate nucleated along the grain boundary shaPed as thin bap andhad no fixed relation with the Cu matrix. The second phase precipitated within thegrain had different shapes of sphere, ellipsoid and long ellipsoid, and had comPlexsemicoherent relation with the Cu matrix. A coherent precipitate had been observedin the CuCr alloy after cold working, and the tiny sphere-shaPed precipitatescattered dispersiveIy in the matrix.