粉末热挤压Al-Zn-Mg-Cu合金的制备工艺及组织性能研究

采用粉末热挤压法制备了一种Al-Zn-Mg-Cu超高强铝合金,研究了粉末粒度和挤压比对合金组织和力学性能的影响。结果表明,400℃挤压时,粉末中位径D50=28.38μm和挤压比λ=25可使挤压合金获得最好的力学性能,挤压合金经过460℃/2.5h水淬+120℃/24h空冷(T6)处理后的抗拉强度、屈服强度和伸长率分别为731MPa,670MPa和6.2%;晶粒细化是挤压合金力学性能随粉末粒度减小而提高的原因;挤压比λ为9～25时,挤压合金力学性能随挤压比增大而提高;λ=36时,挤压合金力学性能降低的原因是MgZn2析出相粗大和发生完全动态再结晶。

Study on Fabrication and Mechanical Properties of Powder Hot Extruded Al-Zn-Mg-Cu Alloy

In this study, an Al-Zn-Mg-Cu ultra strength aluminium alloy was fabricated by powder hot extrusion process, and the effects of powder granularity and extrusion ratio on microstructures and mechanical properties of alloys were investigated. The results show that the optimal powder median size (D_(50)) for the consolidation of alloyed powder is 28.38μm, and the extrusion ratio (λ) is 25. By extrusion at 400℃, the best mechanical properties were obtained with the above as-optimized processing parameters. After T6 temper, i.e. 460℃×2.5h water quenching +120℃×24h air cooling, the tensile strength, yield strength and elongation of the heat treated alloy are 731MPa, 670MPa and 6.2%, respectively. The mechanical properties of extruded alloys increasing with the decrease of powder granularity are due to grain refinement. The mechanical properties of extruded alloys increase with the increase of extrusion ratio from 9 to 25. Coarse MgZn_2 precipitated phases and complete dynamic recrystallization lead to the reducing of mechanical properties of the extruded alloy produced by extrusion ratio 36.