Preparation Of Ultra-fine Grain Copper Strip By Large Strain Extrusion Machining

With the rapid development in the fields of aviation, aerospace technology, militaryequipment and transport, requirements for the performance of metallic materials becomeincreasingly high. With excellent physical and chemical properties, nanocrystalline/ultra-finegrain material is widely used in various fields, the preparation process ofnanocrystalline/ultra-fine grain (UFG) materials also become the research focus.Large strain extrusion machining (LSEM), which has many unique advantages, is one ofthe large plastic deformation effective methods of preparation of UFG materials and attractsmore and more attention. It creates very large plastic strains in a single step in LSEM, wherestrip formation is just partially constrained, thus the LSEM strip has a broader range ofapplications and higher utilization.The influence of machining parameters such as rake angle, chip compression ratio,constraining tool corner radius and friction coefficient on variables in plastic deformation area,microstructure and properties of machined strip are conducted in detailed. The effect of rakeangle, chip compression ratio, constraining tool corner radius and friction coefficient onLSEM has also been analyzed. The formation mechanism of chips and machining parametersneeded by UFG strip formation in LSEM is discussed. The result shows that rake angle andchip compression ratio have a significant impact on total shear strain for the strip. The rakeangle decreases or strip thickness decreases will cause effective strain and strain rate increases.What’s more, the smaller the rake angle or chip compression ratio is, the smaller the grainsizes in the microstructure are obtained. With the constraining tool corner radius or thefriction coefficient increases, the strip effective strain, temperature, stress on the strip alsoincrease, which can impact the microstructure and mechanical properties and corrosionresistance of the strip. Therefore, they play a critical role in the deformation during the LSEMprocess.