冷轧变形量对5A02铝合金管材组织和性能的影响

Effect of Cold Rolling Reduction on Microstructure and Properties of 5A02 Aluminum Alloy Tubes

在室温下,对热挤压态5A02铝合金管材进行四种不同工艺参数(A～D)的两道次冷轧,四种工艺均将尺寸为Φ65. 5 mm×5. 5 mm(外径×壁厚,下同)的坯料冷轧成尺寸为Φ58 mm×2. 5 mm的管材,总冷轧变形量为57. 6%。第一道次与第二道次冷轧变形量(%)分别是:A工艺(20. 2%、47. 3%),B工艺(34. 4%、35. 9%),C工艺(43. 6%、25. 4%),D工艺(52. 7%、11. 1%)。两道次冷轧后的管材均采用410℃/1 h完全退火处理。利用金相显微镜、扫描电镜(SEM)、能谱仪、电子万能试验机等对冷轧管材的显微组织、力学性能、拉伸断口形貌等进行分析,研究冷轧变形量对5A02铝合金管材组织与性能的影响。A～D工艺第一道次冷轧后晶粒与第二相逐渐变小,抗拉强度与断裂延伸率逐渐变大; D工艺第二道次冷轧后管材的晶粒最细小,晶粒尺寸在15～55μm,抗拉强度为186 MPa,断裂延伸率为29%; A～D工艺第二道次冷轧后第二相大小及分布均匀。结果表明:随着冷轧变形量逐渐变大,管材晶粒逐渐变小,力学性能变好;在总冷轧变形量相同的情况下,单道次变形量大的冷轧工艺退火后获得的晶粒更细小均匀,力学性能更好;第二相粒子的尺寸随着冷轧变形量的逐渐增大而变小,在总冷轧变形量相同的情况下,第二相粒子的尺寸也相同。

At room temperature,two-pass cold rolling of hot extruded 5A02 aluminum alloy tubes were processed with four different process parameters(A-D).Billets with size of 65.5 mm×5.5 mm(outer diameter*wall thickness,same below)were cold rolled into tubes with size of 58 mm×2.5 mm,with a total reduction of 57.6%.The reduction(%)of first and second pass cold rolling was as following respectively:A(20.2%,47.3%),B(34.4%,35.9%),C(43.6%,25.4%),D(52.7%,11.1%).After each pass of rolling,the tubes were fully annealed at 410℃/1h.To figure out effect of cold rolling reduction on microstructure and properties of 5A02 aluminum alloy tubes,themicrostructure,mechanical properties,and tensile fracture morphology of cold-rolled tubes were observed and analyzed by means of metallographic microscope,scanning electron microscope(“SEM”),energy spectrometer and electronic universal testing machine.The results are as below:for A-D,after the first cold rolling,grain size and second phase become smaller gradually,while tensile strength and breaking elongation become larger gradually;for D,after the second cold rolling,grain size is smallest within 15-55μm,tensile strength is 186 Mpa,and breaking elongation is 29%;for A-D,after the second cold rolling,second phase is the same in size and distribution.The above results show that:with the reduction of cold rolling becomes largergradually,grain size of the tubes become smaller and mechanical properties become better;under the circumstance that total rolling reduction keeps the same,after cold rolling with large reduction in single pass,the grain of the annealed tubes is smaller and more uniform,and its mechanical properties are better;the size of the second phase particles decreases with the increase of cold rolling reduction,and under the circumstance that total rolling reduction keeps the same,the size of the second phase keeps the same as well.