Preparation Of Ultrafine Crystalline Aluminum Alloy By Large Strain Extrusion Machining And Study On Its Mechanical Performance

Due to the fine grains, the high density of dislocations and defects, ultrafine/nano crystallinemetal material usually exhibits much more excellent physical and chemical propertities andattracts lots of attention. As one of the newly developed method for preparation ofultrafine/nano crystalline metal material, large strain extrusion machining shows manyadvantages and it has been paid more attention to in recent years. However, there are fewstudies on these aspects such as proper selection and disadvantages of this process, and themechanical performance of ultrafine/nano crystalline metal material that prepared by thisprocess. Therefore, it is necessary to conduct sufficient researches and make the application oflarge strain exstrusion machining clearer.In this paper, the3D thermomechanical model of large strain extrusion machining isestablished by adopting the finite element analysis software-Deform3D. The effect of theextrusion cutting parameters such as chip compression ratio, tool rake angle, frictioncoefficient between tool and chip and the maching velocity on the value of effective strain,effective strain rate, effective stress and temperature, and their distribution uniformity in theextrusion cutting deformation zone, along the thickness and width of the chip, and the chipmorphology has been fully studied. Based on the result of the finite element analysis and theactual cutting tests, the optimum extrusion cuttting parameters have been obtained for largestrain extrusion machining. Aluminum alloy with ultrafine grains has been successfullyprepared and the disadvantages of this process have been also made clear. The studies onmechanical performance of the ultrafine crystalline aluminum alloy metal material show thatthe mechanical performance of aluminum alloy such as Vickers hardness, tensile strength,friction and wear properties have been enhanced with varying degrees. The change reason ofthe mechanical performance of aluminum alloy and the influence of the chip compressionratio and tool rake angle on the mechanical performance have been analyzed by using themetallographic microscope, super depth of field microscope and scanning electronicsmicroscope.