5A02铝合金背压式梯度挤镦工艺数值模拟与实验研究

Numerical simulation and experimental study on back-pressure gradient extrusion upsetting process of 5A02 aluminium alloy

以5A02铝合金为研究对象,在300℃下,采用具有“多梯度层”结构的背压式梯度挤镦工艺对其进行了变形,模拟分析了5A02铝合金背压式梯度挤镦工艺的变形行为;对变形试样进行了显微组织观察和显微硬度测试。结果表明:背压式梯度挤镦工艺具有明显的变形细化效果,经过多层梯度挤镦变形,累积等效应变显著增大且呈梯度分布;试样进入下层梯度层发生了复合挤镦阶段变形,此时材料变形程度最为剧烈,挤压载荷增幅最大。1道次变形结束后,试样第1层心部及表层的晶粒尺寸分别为25.7和23.4μm;经过多层梯度成形,单元发生剪切、压缩和拉伸等多种不同形式的复合变形,晶粒得到明显的细化,试样尾端心部及表层的平均晶粒尺寸分别细化为7.8和2.1μm,较起始梯度层细化率达70%和91%。此外,力学性能显著提高,其中试样尾端心部及表层材料的显微硬度分别为95.30和103.50 HV,较初始试样分别提升54%和67%。

5A02 aluminum alloy was deformed at 300℃by the back-pressure gradient extrusion upsetting process with a“multi-gradient layer”structure,and the deformation behavior of 5A02 aluminum alloy in back-pressure gradient extrusion upsetting process was simulated and analyzed.Microstructure observation and microhardness test of the deformed specimens were carried out.The results show that the back-pressure gradient extrusion upsetting process has an obvious deformation refinement effect,after multi-layer gradient upsetting and extrusion deformation,the accumulated effective strain increases significantly and shows gradient distribution.The specimen enters the lower gradient layer and experiences the compound upsetting and extrusion stage deformation,at this time,the material deformation degree is the most intense and the increase of extrusion load is the maximum.After one pass deformation,the grain size at the core and surface of the first layer of the specimen is 25.7 and 23.4μm,respectively.After the multi-layer gradient forming,the unit experiences various forms of compound deformation such as shear,compression,and tension and the grain is refined abviously.The average grain size at the core and surface layers at the end of specimen is 7.8 and 2.1μm,respectively,with a refinement rate of 70%and 91%compared to the original gradient layer.In addition,the mechanical properties are significantly improved,the microhardness at the core and surface layers at the end of the specimen is 95.30 and 103.50 HV,respectively,which increase by 54%and 67%compared to the initial specimen.