The Research On Deformation Behavior And Organizational Performance Of Al And Al-3%Si Alloys During ECAP

ECAP makes the materia obtain a larger amount of strain accumulation by changing the extrusion path and extrusion passes,achieving grain’s refinement, improving the material of organization and performance. ECAP is an effective way to make ultrafine-grained materials. Al and Al-3%Si alloy were five inferior ECAP at room temperature, studying the deformation behavior and organizational performance of ECAP.Al-3%Si alloy was prepared,the copper was fixed in the center of Al-3%Si alloy by self-designed casting mold, it was five inferior ECAP at room temperature. study ing the deformation behavior of ECAP by the shape and location of the copper. Analyzing the extrusion deformation from macro to micro by OM,SEM,XRD. It was showed that materials was affected by the torsiona,the copper deflected by counter-clockwise from one timf to five times times in A path squeeze,the grain size of a-Al matrix was refined from70μm to10μm, the eutectic Si was refined from50um to4um, the eutectic Si was crushed from elongated shape to granular, Simultaneously the eutectic Si Segregated, the dominant crystal orientation was became from (220) to (111); the copper deflected from one pass to five passes in Bc path squeeze, the copper deflected by clockwise in two passes and five passes, the copper deflected by counter-clockwise in three passes and four passes, the grain size of a-Al matrix was refined from70μm to8μm, the eutectic Si was refined from50um to4um, Its elongated shape was broken granular, Finally, the eutectic Si uniformly distributed in the matrix a-Al, the intensity of the hard crystal orientation (111) became low at2passes and4passes, the intensity of the soft crystal orientation(111)increased at3passes and5passes,(200)and(111) are opposite; the copper deflected from one pass to five passes in Ba path squeeze, the copper deflected by counter-clockwise in2passes and4passes, the copper deflected by clockwise in3passes and5passes, the intensity of the hard crystal orientation (111) became low at2passes and5passes, the intensity of the soft crystal orientation (111) increased at3passes and4passes,(200)and(111) are same.The sample surface of Al-3%Si alloy appeared Cracks partly, analysising the mechanism of crack initiation and propagation by observation of the crack and microstructure, the deformation of material surface was violent during ECAP, the brittle eutectic Si was broken, deviating matrix a-Al and appearinng accompanied pits, The stress concentration caused the brittle eutectic Si and holes produced at the crack. The crack propagation was produced by the shear and surface tensile stress.the crack propagated transversely under the surface tensile stress, the crack propagated Longitudinally under the shear force, the crack bypassed the brittle eutectic Si during expansion. Resulting the topography of crack was uneven, the trajectory of crack almost parallelled the shear plane. the industrial aluminum squeezed the sample through remelting and refining, the sample carried out5passes ECAP. the sample was tested by TEM and hardness, Analysising the refinement mechanism of the high-level fault energy materials, Analysising the tensile strength, elongation, hardness variation of the aluminum during ECAP, the aluminum high-rise fault energy material, its refinement mechanism is dislocation split mechanism, the dislocation density increased rapidly from lpass to5passes, the dislocation density is5.4×1015after lpass, the dislocation density is8.0×1015after5passes. The tensile strength of casting aluminum is85Mpa, the tensile strength is168Mpa after five passes, the tensile strength increased by97.6%compared the Original sample, The elongation of casting aluminum is45%, the elongation is21%after5passes, the elongation increased by53.3%compared the Original sample,the minimum elongation is17.5%after3passes,the hardness of casting aluminum is23.8kg/mm2,the hardness of casting aluminum is53kg/mm2after3passes.