异速轧制和常规轧制对7075铝板力学性能的影响

Effect of asymmetrical and symmetrical rolling on mechanical properties of 7075 aluminum plates

  • 摘要: 为进一步开发更高效的7075铝板轧制工艺,本文围绕异速轧制和常规轧制对7075铝板力学性能的影响开展了研究,并采用了4个不同的轧制累积变形率。实验分2步进行,第1步为轧板弯曲程度随异速比变化实验,将轧板弯曲内面朝向水平底面放置,测量弯曲内面最高点距离水平底面距离y,以及弯曲内面与水平底面的两接触点距离x,用y/x值表征轧板的弯曲程度;第2步为异速和常规轧制实验。实验结果表明:当异速比为1.12时,轧板弯曲程度最大,y/x值最高达到0.222 18;虽然采用了相同的设计累积变形率,但异速轧制和常规轧制的轧板实际累积变形率相差1%~2%;两种方式轧制的轧板在实际累积变形率达到76%时,T6热处理过程中再结晶进行得更加充分,再结晶生成的中小尺寸晶粒增多;经过6道次异速轧制和常规轧制的7075铝板,T6热处理后,断口中可见大量尺寸小于1 μm的韧窝,并且在韧窝底部出现弥散析出的尺寸小于100 nm的微小第二相粒子,异速轧制7075铝板中韧窝尺寸较常规轧制7075铝板中更细小;与常规轧制相比,采用异速轧制的7075铝板的强度有一定提高,但提高幅度不大;常规轧制的7075铝板在达到一定变形量时会出现强度峰值,而异速轧制的7075铝板的强度随轧制累积变形率升高而持续提高。

     

    Abstract: To further develop a highly efficient rolling process for 7075 aluminum plates, this paper carried out an experimental study on the effects of asymmetrical and symmetrical rolling on the mechanical properties of 7075 aluminum plates, and adopted four different rolling cumulative deformation ratios. The experiment was conducted in two steps. The first step was an experiment on the variation of the bending degree of the rolled plate with different asymmetrical rolling speed ratios. The distances y between the highest point of the inner bent surface and the horizontal bottom surface, and the distance x between the inner surface's two contact points of the bent inner surface and the horizontal bottom surface were measured, with the inner surface of the rolled plate facing the horizontal bottom surface. The y/x value was used to describe the bending degree of the rolled plate. The second step was asymmetrical and symmetrical rolling experiments. The experimental results show that the bending degree of the rolled plate is the maximum when the speed ratio is 1.12, and the y/x value can reach 0.222 18. However, even though the same design cumulative deformation rate is used, the actual cumulative deformation ratios of the rolled plates produced by asymmetrical and symmetrical rolling differ by 1% to 2%. When the actual cumulative deformation rate of the rolled plate reaches 76%, the recrystallization in the rolled plates is more effective during T6 heat treatment, and the amount of small and medium-sized crystal grains generated by recrystallization increases. After T6 heat treatment, a large number of dimples with a size of less than 1 μm and small second phase particles with a size of less than 100 nm can be visible in the fracture of the 7075 aluminum plates after 6 passes of asymmetrical and symmetric rolling. Asymmetrically rolled 7075 aluminum plate has smaller dimples than that in symmetrically rolled. Compared with symmetrical rolling, asymmetrical rolling just slightly increases the strength of the 7075 aluminum plate. When a specific level of deformation is reached, the strength peak of the 7075 aluminum plate rolled symmetrically will appear. However, the strength of the 7075 aluminum plate by asymmetrically rolling continually increases with increasing rolling cumulative deformation ratio.

     

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