挤压、轧制变形对高强度Mg-Gd-Y-Zn-Mn合金组织性能的影响研究

发布时间：2018-03-23 08:52

  本文选题：高强镁合金　切入点：LPSO相　出处：《重庆大学》2015年硕士论文　论文类型：学位论文

【摘要】：镁合金作为目前最轻的金属结构材料,具有比强度高、减振性好和易回收等优点,在航天航空、国防军工、交通运输和电子产品等领域都具有广阔的应用前景。然而镁合金的绝对强度偏低,制约了镁合金的应用发展。近年来,研究开发的Mg-RE-Zn系变形镁合金由于LPSO相和时效沉淀相的复合强化作用,强度可以达到500MPa以上,但是关于Mg-RE-Zn系合金塑性变形规律的研究还比较缺乏。挤压和轧制变形能够有效调控镁合金的组织和性能,且能够应用于棒材、管材、型材和板材的大规模生产,对于促进镁合金的生产应用具有重大意义。为此本文针对挤压、轧制变形对高强度Mg-9.23Gd-3.29Y-1.24Zn-0.87Mn(wt%)合金组织性能的影响开展了研究。首先,研究了挤压比(8,11,27和42)对均匀化退火态合金组织性能的影响。均匀化退火后,合金中析出大量层状LPSO相。挤压比为8和11时,合金的再结晶程度较低,层状LPSO相趋于与挤压方向平行分布,形成大量层状变形组织,合金的塑性较低。随着挤压比的增大,再结晶程度逐渐增大,塑性逐渐提高,但抗拉强度相差不大。时效处理后,各合金的抗拉强度出现一定的差距。挤压比为11的棒材时效态合金具有最高的强度,UTS=502MPa,YTS=410MPa,EL=3.8%。此外,制备了挤压比为11的挤压板材,合金中同样主要为层状组织,时效后也获得了不错的力学性能。然后,研究了轧制变形对合金组织性能的影响。均匀化退火态合金轧制变形参数的探索中,发现由于层状LPSO相对再结晶具有强烈抑制作用,在450℃下轧制容易开裂。均匀化退火态合金在520℃下轧制后,仍存在层状变形组织,塑性较差。而对铸态合金进行“轧制+固溶+轧制”工艺处理后,合金中块状LPSO相较小,且分布弥散,合金的晶粒较为均匀,具有较高的塑性。对比来看,“轧制+固溶+轧制”工艺容易进行更大下压量的轧制。最后,研究了轧制变形对挤压态合金组织性能的影响。对于含有大量层状组织的挤压合金,轧制变形中,层状组织逐渐减少,再结晶组织逐渐增多,但晶粒尺寸无明显变化。对于以等轴晶组织为主的挤压合金,轧制变形后,晶粒略微细化。对挤压合金进行轧制变形后,合金的屈服强度都有所提高,但是塑性急剧降低。挤压比11的棒材合金在“轧制(下压量50%)+时效”处理后,具有较高的强度,UTS=511MPa,YTS=430MPa,EL=2.6%。
[Abstract]:As the lightest metal structure material at present, magnesium alloy has the advantages of high specific strength, good vibration absorption and easy recovery. Transportation, electronic products and other fields have broad application prospects. However, the absolute strength of magnesium alloy is low, which restricts the development of magnesium alloy application in recent years. The strength of the developed Mg-RE-Zn wrought magnesium alloy can reach above 500MPa due to the composite strengthening effect of LPSO phase and aging precipitation phase. However, the study on the plastic deformation of Mg-RE-Zn alloys is still lacking. Extrusion and rolling deformation can effectively control the microstructure and properties of magnesium alloys, and can be used in large-scale production of bars, pipes, profiles and plates. Therefore, the effect of extrusion and rolling deformation on the microstructure and properties of high strength Mg-9.23Gd-3.29Y-1.24Zn-0.87Mnwtmeter alloy is studied. The effect of extrusion ratio of 8 / 11 / 27 and 42) on the microstructure and properties of homogenized annealed alloy was studied. After homogenization annealing, a large number of layered LPSO phases were precipitated in the alloy. The recrystallization degree of the alloy was lower when the extrusion ratio was 8 and 11:00. The lamellar LPSO phase tends to distribute parallel to the extrusion direction, forming a large number of lamellar deformed microstructure, and the plasticity of the alloy is lower. With the increase of extrusion ratio, the recrystallization degree and plasticity gradually increase, but the tensile strength of the alloy increases gradually, but the tensile strength is not different. The tensile strength of each alloy has a certain gap. The aging alloy with extrusion ratio of 11 has the highest strength. In addition, the extruded sheet with extrusion ratio of 11 is also mainly layered structure. The effect of rolling deformation on the microstructure and properties of the alloy was studied. In the exploration of rolling deformation parameters of homogenized annealed alloy, it was found that the relative recrystallization of layered LPSO was strongly inhibited. It is easy to crack after rolling at 450 鈩，

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