工艺参数对CVCE变形工业纯铝组织和性能的影响

Microstructure and Properties of Commercial Pure Aluminum CVCE Deformed at Different Processing Parameters

采用连续变断面循环挤压(CVCE)工艺制备细晶工业纯铝,结合金属流动规律研究挤压角度和变形道次对变形工业纯铝组织和性能的影响。结果表明:随着挤压角度的增加,网格畸变程度和变形不均匀程度随之增加,θ=7°试样的晶粒细化程度远大于6°,但晶粒尺寸和晶粒分布不及6°均匀;随着变形道次的增加,累积变形量增大,晶粒被充分细化,θ=7°试样经3个循环变形后的晶粒尺寸被细化至10μm,是原始晶粒尺寸的1/10; CVCE变形工业纯铝由表面至芯部的网格畸变决定了硬度的分布是沿表面到芯部逐渐减小,并且随着变形道次的增加,θ=7°试样的硬度呈显著增加趋势,3个循环的显微硬度可达HV 105. 62,相比于原始试样提高了4倍。经CVCE变形后试样,横截面与纵截面上晶粒的形状和取向性完全不同,纵截面上原始等轴晶粒取向性逐渐削弱,横截面上原始粗大的柱状晶经过变形后,晶粒的取向性几乎消失。

Combined with the metal flow,the effect of extrusion angle and continuous variable cross-section recycled extrusion( CVCE) passes on the microstructure and mechanical properties of fine grain commercial pure aluminum processed by CVCE technique was investigated. The results showed that the degree of grid distortion and heterogeneous deformation increased with the enlargement of extrusion angle,and the sample of θ = 7° had higher grain refinement level but less uniform grain size and distribution than 6° accordingly. The size of grains were fully refined to a smaller scale and accumulative deformation increased with the accumulation of deformation passes,ultimate grain size of θ = 7° sample could reach 10 μm after three circles,which was 10% of original sample. The distribution that microhardness slightly decreased from the surface to the center along the longitude and latitude direction depended on the grid distortion,the microhardness was significantly improved by means of increasing CVCE passes and saturated to HV 105. 62 after three circles,which was improved by 4 times compared with original samples. The samples after deformation had quite different grain shape and orientation on cross section and longitudinal section,the orientation of original equiaxed grain gradually weakened on longitudinal section but the orientation of original thick columnar crystals almost disappeared on cross section.