Research On Size Effect Of Microplastic Forming Of Copper Alloy Sheet

With the rapid development of science and technology,the application of micro-parts has become more and more extensive,and it has broad application prospects in microelectronics and other industries.Plastic forming technology has many advantages that other forming technologies do not have,such as mass production,high precision,low production cost,etc.Therefore,a new forming technology-microplastic forming technology has been gradually formed in the research process of micro devices.This technique utilizes plastic deformation to machine micro-components in the order of millimeters to micrometers in at least two dimensions,which is the most promising method for preparing micro-parts.When the material size is reduced to a certain extent,the mechanical properties and physical properties of the material during the forming process will exhibit a size effect phenomenon.Based on this,the size effect of the micro-plastic forming of H65 brass and T2 copper sheet is studied,and the following research results are obtained:(1)Different thicknesses of H65 brass sheet and T2 copper sheet obtained by cold rolling were heat treated by different heat treatment processes,and the deformation law of the internal microstructure of the material obtained under different process conditions was analyzed.The results show that the equiaxed grains inside the as-rolled sample are flattened and elongated in the rolling direction,and the grain fragmentation is serious.The dislocation entanglement forms a high-density substructure and fibrous structure appears.When the material thickness is the same,the higher the annealing temperature,the larger the grain size;when the heat treatment process is the same,the grain size decreases as the thickness decreases.(2)The size effect of H65 brass under different test factors and its influence on mechanical properties were studied by uniaxial tensile test.The results show that the tensile strength increases with the decrease of the thickness and the elongation decreases with the decrease of the thickness.At the micro scale,the mechanical properties of the material are not sensitive to the strain rate.Compared with large scale,70?m thickness of specimen on its mechanical properties in different rolling direction change is not obvious;The yield strength and tensile strength of annealed samples at different thicknesses decreased with the increase of grain size.(3)The effect of the size effect of T2 copper in different process states on the mechanical stress-strain relationship was studied by tensile test.The results show that the tensile strength and yield strength of the material increase first and then decrease with the decrease of specimen thickness.The rolling direction has little influence on the mechanical properties of the material when the test thickness is very small.For sample annealed state,when the thickness is not at the same time,the flow stress of material as ?(t/d)value increases,the phase at the same time,the specimen thickness as ? value decreases,and the tensile strength and elongation decrease as a whole.(4)The effects of different test parameters on the bending springback of H65 brass and T2 copper specimens were investigated by microbending test.The results show that both materials decrease with the thickness of the blank,and the bending resilience of the sample increases gradually,and the rebound rate of brass is higher than that of copper,which is related to the mechanical properties of the material;when the thickness of the sample is the same,The amount of springback of the two material bending members gradually decreases as the grain size increases.When the material is kept constant in thickness,the amount of springback of the bent piece increases as the bending angle increases.(5)In the cold rolling process,as the amount of rolling deformation increases,the roughness of the surface of the two material parts gradually decreases.In the bending process,when the thickness is the same,the surface roughness of the two materials increases with the increase of the grain size and bending angle.The microhardness of H65 brass increases with the increase of rolling deformation.The microhardness of T2 copper increases first and then decreases with the increase of rolling deformation.When the thickness is the same,the microhardness of the two materials decreases with the increase of the grain size,and the microhardness of the annealed material increases with the increase of the thickness.