Study On Evolution Of Microstructures And Properties Of Pure Copper And Aluminum In Equal Thickness Extrusion And Heat Treatment

Grain refinement is an important way to improve the comprehensive properties of metallic materials.The Sever Plastic Deformation(SPD)has aroused echoes among the scholars by which can refine grains substantially.The existing SPD processes,however,have their owned difficulties in manufacturing bulk fine grain materials and utilizing in industrialized production.In this paper,a series of SPD experiments were carried out on pure copper and pure aluminum strip by using group-developed continuous equal thickness extrusion equipment.The effects of different deformation steps,die parameters and heat treatment on Microstructure and properties were studied.The experiment above is of great significance for industrial application and developing technology of fabricate ultra-fine grain metallic material.T2 industrially pure copper and 1060 pure aluminum strip with thickness of 2 mm was selected as the object of study in this paper.Microstructures and properties of copper and aluminum strip during the process of equal thickness extrusion and heat treatment were studied.The main results are as follows.(1)The pure copper deformed by deffident dies with deffirent strain exhibit deffident degrees in grain refinement during the equal thickness extrusion.Microstructures of the pure copper strip deformated 16 passes by using the die with a channel angle of 125°(single pass deformation is 0.57)were analyzed.The the cross section and the longitudinal section average grain sizes of the sample are reduced from 11.57 ?m and 18.17 ?m to 5.92 ?m and 7.88 ?m respectively.While the average cross section and longitudinal section grain sizes of the samples which deformated by the die with 120° channel angle(single pass deformation is 0.635)are reduced from 9.63 ?m and 11.73 ?m to 5.73 ?m and 5.95 ?m respectively,and the hardness increased from 104.83 Hv to 142.24 Hv.(2)The equal thickness extrusion can effectively refine the grains of pure aluminum strip.Microstructures of the pure aluminum strip deformated 3 passes by using the die with a channel angle of 120°were analyzed.The the cross section and the longitudinal section average grain sizes of the sample are reduced from 47.57 ?m and 4623 ?m to 24.12 ?m and 26.19 ?m respectively,and the hardness increased from 64.08 Hv to 81.27 Hv.(3)The effect of different annealing schemes on Microstructures of the deformed materials was studied.The results indicate that the multi-stage high temperature short time annealing scheme contributes to grain refinement The cross and longitudinal sections average grain size of the pure copper strip deformated 6 passes by using the die with a channel angle of 125° changed from 6.61 ?m and 11.35?m to 6.19 ?m and 7.81 ?m after annealing by 420? ×(1+1+1)min,respectively,and the average grain size was more uniform and the degree of anisotropy was improved(4)The tensile properties of the deformed metal have already improved.The yield strength and tensile strength of the pure copper strip deformated 4 passes by using the die with a channel angle of 120° after annealing by 350? ×(1+1+1)min increased from 160.81 MPa and 247.78 MPa to 310.35 MPa and 324.56MPa The yield strength and tensile strength of the pure aluminum strip deformated 3 passes by using the die with a channel angle of 120°after annealing by 250?×(1+1+1)min increased from 45.36 MPa and 65.96 MPa to 181.16 MPa and 193.26 MPa.(5)There is no definitely difference in microstructure between samples get out of die with pulling and entirely by extrusion.This paper shows that the equal thickness extrusion can effectively refine the grains and enhance the strength of the material,which has important reference and theoretical value for the research in industrial processing and heat treatment of the fine grain.