Study On The Mechanism Of Plasticity Of Copper Alloy After Large Plastic Deformation

Copper alloys which is with its excellent electrical conductivity, thermal conductivity, ductility and corrosion resistance, mainly are used in the production of generators, bus bar, cable, switchgear, transformers, other electrical equipment and heat exchangers, piping, solar heating device thermal equipment such as flat plate collector. As a famous nonferrous metal kingdom, the development and application of copper and copper alloys of Yunnan is in the top over the country. Recently, people get more attention to prepare ultrafine crystal/nanomaterials through the severe plastic deformation processing method. The mechanical properties and microstructure of ultrafine crystal/nanomaterials which is processed through the large plastic deformation of preparation is differ from the ordinary coarse grain materials.As the raw material of copper zinc alloy, copper aluminum alloy in this topic:Cu、 Cu-10wt.%Zn、Cu-20wt.%Zn、Cu-30wt.%Zn, Cu-2.2wt.%A, Cu-4.5wt.%Al,this article mainly explores mechanical properties and microstructure of the copper zinc alloy, copper aluminum alloy which were processed by severe plastic deformation mainly explores the ways for copper zinc alloy, the copper zinc alloy which is annealed at short time and a low temperature, the abnormal hardening copper zinc alloy which is reduced50%by room rolling, in order to obtain the best mechanical properties. The main mechanical properties tests and analysis of microstructure methods:micro hardness test, tensile test, XRD.By the compare the mechanical properties of samples which was rolled at room temperature and liquid nitrogen temperature, the samples which was rolled at room temperature has a better mechanical properties than the samples which was rolled at liquid nitrogen temperature. Found by experiment, the deformation temperature is an important influence on the material mechanics properties:the lower deformation temperature, the more favorable for the formation of twin,it is easy to product much twin. Like this, it is more easily to improve the work hardening rate by plug productive dislocation. And the twin boundary which is equal to the large angle grain boundaries is favor of refining the grain size, thus improving the strength and ductility of materials at the same time.By compare mechanical properties of copper aluminum alloy samples which have different composition and were processed by high pressure torsion, we found the lower stacking fault energy the more easily product the twin and stacking fault. The lower stacking fault energy, the wider stacking fault, it is easily to plug the dislocation and improve the work hardening rate. It is easily not only improves the strength but also improves the ductility at the same time. In this way, we can achieve the optimal mechanical properties. But the mechanics property of material is influenced by many factors, it is not the lower stacking fault energy, the better mechanics property.By compare mechanical properties of copper aluminum alloy samples which have different composition and were processed by high pressure torsion and rolled at room temperature(the strain of high pressure torsion is8.84,the strain of room rolling is2.98),we can found the bigger strain can make the grain more smaller.In addition, it is usually that the ultrafine grain/nanomaterials which was annealed at short time and low temperature showed the abnormal hardening phenomenon in recent years.In this experiment,we use the Cu-10wt.%Zn、 Cu-20wt.%Zn、Cu-30wt.%Zn which were annealed:(1) produce annealing twin inside the material;(2) to eliminate the internal stress and material defects for the sake of improve the comprehensive mechanical properties of materials. We found the yield strength of RR Cu-30wt.%Zn samples which was annealed at200℃and250℃was improved obviously; the yield strength of LNR Cu-20wt.%Zn samples which was annealed at150℃and LNR Cu-30wt.%Zn samples which was annealed at100℃and150℃was improved obviously.Among the abnormal annealing hardening copper zinc alloys samples, we select LNR Cu-20wt.%Zn samples which was annealed at150℃temperature and1h, the samples was rolled at room temperature again. Through mechanical properties test and microstructure analysis, we found the yield strength and tensile strength of the samples has a small reduction, but the uniform elongation has an obvious increasing at the same time.