摘要:
分别采用9:1和25:1挤压比以及450 ℃ 和500 ℃ 挤压温度，将6063铝合金碎屑通过固结成形，然后进行T6热处理制备成样品，并对样品的微观组织，拉伸力学性能以及断裂行为进行研究。结果表明：当挤压温度为500 ℃ 时，热挤压碎屑制备的材料发生再结晶，再结晶晶粒被限制在合金屑内，多数呈拉长状态，随着挤压比的提高，晶粒明显细化，导致屈服强度和抗拉强度从198和242 MPa 明显提高到252和275 MPa，延伸率也明显下降（19.5%至15.2%）。把挤压比保持在25:1，随着挤压温度由500 ℃ 降低到450 ℃，热挤压碎屑制备的材料的晶粒尺寸稍有增加，合金的屈服强度和抗拉强度变化不大，延伸率由15.2% 下降到12.1%。为了比较，在同样条件下热挤压铸锭制备了材料样品并进行了T6热处理，发现动态再结晶同样发生，晶粒尺寸随挤压比变化不大，随挤压温度的下降有所下降，但是两种情况力学性能基本不变（屈服强度：192-202 MPa, 拉伸强度：228-237 MPa, 延伸率：18.4-19.1%）。两种材料均展示塑性拉伸断裂，但断裂方式有所不同，固结碎屑制备的材料发生了碎屑之间的剥离。本文也讨论了工艺条件、微观组织和力学性能之间的对应关系。
Abstract:
6063 aluminum alloy samples were prepared by thermomechanical consolidation of alloy chips which involves hot extrusion of chip compacts with extrusion ratios of 9:1 and 25:1 and extrusion temperatures of 450 ℃ and 500 ℃, respectively, followed by a T6 heat treatment. The microstructure , tensile properties and fracture behavior of the samples were studied. The results show that with an extrusion temperature of 500 ℃, dynamic recrystallization occurs in the consolidated samples, and the recrystallized grains are confined within the chips and become elongated. With the increase of extrusion ratio, the grains become finer, the yield strength (YS) and ultimate tensile strength (UTS) increase from 198 and 242 MPa to 252 and 275 MPa, respectively, and the elongation to fracture decreases clearly from 19.5%-15.2%. With an extrusion ratio of 25:1, an decrease of the extrusion (EL) from 500 ℃ to 450 ℃ caused a slight increase of the average grain size, the YS and UTS remain almost unchanged, and the elongation to fracture decreases clearly from 15.2% to 12.1%. For comparison, 6063 aluminum alloy samples were also prepared by hot extrusion of ingots under the same conditions followed by the same T6 heat treatment. It was found that the average grain size changes little with the increase of extrusion ratio, but decreases slightly with the decrease of extrusion temperature. The tensile properties remain almost unchanged in these two cases (YS: 192-202 MPa, UTS: 228-237 MPa, EL: 18.4-19.1%). Both types of materials exhibit ductile tensile fracture, but the mode of fracture is different, with the material prepared by consolidation of chips shows interchip decohesion. Correlations among processing conditions, microstructure and mechanical properties are discussed.
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