简介概要

不同预弯半径下2A12铝合金时效成形

来源期刊:中国有色金属学报2011年第2期

论文作者:赵飞 周文龙 孙中刚 陈国清 黄遐 曾元松

文章页码:303 - 310

关键词:2A12铝合金;时效成形;回弹;应力位向效应;力学性能

Key words:2A12 aluminum alloy; age forming; springback; stress orientation effect; mechanical properties

摘    要:研究2A12铝合金在不同预弯半径下的时效成形,并考察时效成形与人工时效后合金的微观组织和力学性能的差异。结果表明:与人工时效相比,时效成形过程中,由于应力的存在,使得合金在时效成形后晶粒被进一步压扁拉长,晶内沉淀相由点状变为长条状且呈现出一定的方向性,同时,其位错形态由位错圈或蜷线位错向长直态位错转变。时效成形后,合金的拉伸性能和断裂韧性均比人工时效时的略有降低,回弹率随预弯半径的增大而增大。预弯半径的变化对沉淀相的尺寸和数量以及时效成形后合金的力学性能均无明显影响。

Abstract: The age forming of 2A12 aluminum alloy subjected to different prebending radii was investigated. The differences of microstructures and mechanical properties after aging forming and artificial aging were also studied. The results show that, during artificial aging, the grains are further squashed and elongated due to the applied stress during age forming and the precipitated phase changes from circle shape to long strip shape with uniform orientation. Further, the dislocation configuration in samples subjected to age forming changes from ring dislocation or helical dislocation to long and straight dislocation. However, the age forming decreases slightly tensile properties and the fracture toughness of the alloy and increases its springback with prebending radii increasing. There is no significant influence of the variation of prebending radius on the size and number of the precipitated phase, as well as the mechanical properties of the alloy after age forming.



详情信息展示

图9  2A12铝合金经人工时效和时效成形后的拉伸性能

Fig.9  Tensile properties of 2A12 aluminum alloy after artificial aging and age forming: (a) Yield strength and tensile strength; (b) Elongation

图10所示为2A12铝合金于(160 ℃,3 h)和(190 ℃,6 h)时效成形及人工时效后的断裂韧性对比。由图10可以看出,在相同温度和时间下,时效成形后的断裂韧性无论是L-T方向还是T-L方向均比人工时效时的低。由于时效成形后沉淀相的分布具有方向性,对延缓裂纹扩展不利,且材料的伸长率也较低,造成时效成形后合金的断裂韧性下降;在相同温度和时间、不同预弯半径下,时效成形后沿同一取向的断裂韧性基本相同;同一状态下,材料L-T方向的断裂韧性均大于T-L方向的断裂韧性。主要是由于铝合金轧制后,晶粒沿轧制方向伸长,晶内难溶相、未溶相和夹杂等也均沿轧制方向排列。在断裂过程中,形成裂纹扩展的通道,降低了合金抵抗断裂能力。在L-T方向(裂纹垂直轧制方向扩展)断裂裂纹扩展过程需经过多次偏转,从而断裂韧性较高。

图10  2A12铝合金经人工时效和时效成形后断裂韧性的 对比

Fig.10  Fracture toughness comparison of 2A12 aluminum alloy after artificial aging and age forming

3  结论

1) 当成形温度和保温时间一定时,2A12铝合金试件的回弹率随预弯半径的增大而增大;而在相同预弯半径下,提高成形温度和延长保温时间可使2A12铝合金试件的回弹率减小。

2) 2A12铝合金经时效成形后的晶粒较经人工时效时的被进一步压扁拉长。时效成形过程中,由于弹性载荷的施加,使得合金在时效成形后析出的沉淀相为长条状,并呈现一定的方向性,而人工时效时析出的沉淀相为点状且分布比较均匀。合金时效成形后的位错形态与人工时效时相比也不一样:时效成形后为长直态位错,而人工时效时为位错圈或蜷线位错。

3) 在相同温度和时间下,2A12铝合金时效成形后的拉伸性能较人工时效时的略有降低,但降幅均在6%以内,可认为时效成形能获得与人工时效过程相近的拉伸性能。

4) 在相同温度和时间下,2A12铝合金时效成形后的断裂韧性比人工时效时的略低。

5) 时效成形过程中,预弯半径的变化对2A12铝合金的微观组织和力学性能几乎没有影响。

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