挤压比对流变挤压成形Al-0.1Fe合金组织性能的影响

Effect of Extrusion Ratio on Microstructure and Properties of Al-0.1Fe Alloy Fabricated by Continuous Rheo-extrusion

目的研究挤压比对流变挤压态Al-0.1Fe合金微观组织演化和力学性能的影响规律,为通过流变挤压成形制备高性能Al材过程中挤压比的选用提供依据与参考。方法采用重力铸造和流变挤压方法制备了Al-0.1Fe合金,对比了铸态和流变挤压态Al-0.1Fe合金的微观组织和力学性能,通过Arrhenius方程建立了晶界迁移速率与温度之间的关系,研究了流变挤压过程中不同挤压比对Al-0.1Fe合金组织性能的影响。结果流变挤压变形可消除铸造过程中形成的粗大枝晶,破碎微米尺寸Al_(3)Fe相,使之转变为细小的等轴晶和纳米尺寸Al_(3)Fe相;当挤压比从4增大至6.25时,流变挤压态Al-0.1Fe合金的晶粒逐渐细化,位错密度提高,纳米尺寸Al_(3)Fe相逐渐球化,合金强度和硬度提高,导电率降低;当挤压比为9时,大量摩擦热和变形热增大了晶界迁移速率,导致流变挤压态Al-0.1Fe合金的晶粒和纳米尺寸Al_(3)Fe相发生粗化,位错密度降低,伸长率和导电率提高。结论在流变挤压成形过程中适当提高挤压比可以细化合金的微观组织,提高合金的力学性能;当挤压比过高时,合金微观组织发生粗化,导致合金的力学性能降低。

The work aims to investigate the effect of extrusion ratio on the microstructure evolution and mechanical proper-ties of Al-0.1Fe alloy fabricated by continuous rheo-extrusion(CRE)forming,to provide reference for selecting extrusion ratio of high-performance CRE Al alloys.Al-0.1Fe alloy was prepared by gravity casting and CRE,respectively.The variation in mi-crostructure and mechanical properties of as-cast and CRE Al-0.1Fe alloy were revealed.The relationship between grain bound-ary migration rate and temperature was established by the Arrhenius equation.The effects of different extrusion ratios on the microstructure and mechanical properties of Al-0.1Fe alloy during CRE were studied.The results showed that the coarse den-drites and micron-sized Al_(3)Fe phases were eliminated,broken,and changed into fine equiaxed grains and nano-sized Al_(3)Fe phases during CRE,respectively.The grains were refined and dislocation density enhancement was achieved in the CRE Al-0.1Fe alloy with extrusion ratio increasing from 4 to 6.25,while spheroidization occurred on nano-sized Al_(3)Fe phases.The strength and hardness increased,but the ductility decreased.As the extrusion ratio increased to 9,the high friction and deforma-tion heat improved the grain boundary migration rate,resulting in the coarsening of grains and nano-sized Al_(3)Fe phases in the CRE Al-0.1Fe alloy.The dislocation density decreased,while the elongation and ductility increased.The microstructure of the alloy can be refined during CRE through appropriately increasing the extrusion ratio,and the mechanical properties can be im-proved as a result.However,the microstructure of the alloy tend to coarsen and mechanical properties decrease during CRE with excessive extrusion ratio.