梯度结构5052铝合金微观结构与力学行为研究

发布时间：2018-01-23 18:36

本文关键词： 梯度结构 5052铝镁合金微观结构演变力学性能 RASP　出处：《南京理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：梯度结构材料因为有望同时获得高强度和高韧性而备受关注,本文采用旋转加速喷丸技术(Rotation Accelerated Shot Peening,RASP)在5052铝镁合金中获得了梯度结构。首先借助TEM表征方法分析了 RASP处理后沿厚度层的微观结构演变;进而对RASP参数,包括RASP时间、RASP速度、RASP温度、板材厚度对5052铝镁合金力学行为的影响进行逐项分析讨论,并与其它变形方式进行对比;最后进行共轧制(Co-rolling)处理,并研究了轧制对5052铝镁合金力学行为的影响。主要结论如下:(1)RASP处理在5052铝镁合金板材表层形成了纳米晶、等轴亚晶和伸长亚晶,位错组态主要有位错缠结、位错墙、位错胞,并且在距离表面的不同位置,位错胞大小不同。(2)RASP时间增加使得5052铝镁合金屈服强度提高,同时韧性下降,屈服强度在50 m/s-10 min处理条件下达到最高值180 MPa,提高了 156%。RASP速度在40 m/s以下时,时间的增加会使得显微硬度曲线整体上升;RASP速度在40m/s及以上时,不同时间处理条件下显微硬度值会在靠近表面的厚度区域内交织在一起,但在靠近心部的深度区域内随着时间的增加而增加。随着RASP速度的增加,屈服强度基本呈线性增加,均匀延伸率也基本呈线性下降。速度的改变使获得的梯度层厚度发生改变。(3)与室温RASP相比,液氮带来的低温在RASP处理过程中起了抑制位错运动的作用,使得同等RASP参数下,获得的变形量较小,具体表现为显微硬度沿厚度层的整体下降;但因为析出强化,获得的屈服强度较高。对不同板材厚度的研究发现,当梯度层体积百分比为0.5左右时,梯度层表现出最佳的变形协同作用,有助于材料同时获得高强度和高韧性。(4)相比于单纯RASP处理,Co-rolling处理后材料的强度得到大幅度提高,但均匀延伸率也急剧下降。保留梯度层的样品获得幅度较小的强度和韧性的同步提高。
[Abstract]:Gradient structural materials have attracted much attention because of their promise to obtain both high strength and high toughness. Rotation Accelerated Shot Peening is used in this paper. RASP) was used to obtain gradient structure in 5052 Al-Mg alloy. Firstly, the microstructure evolution along the thickness layer after RASP treatment was analyzed by means of TEM characterization. Furthermore, the effects of RASP parameters, including RASP time, RASP velocity and temperature, thickness of sheet on the mechanical behavior of 5052 Al-Mg alloy were analyzed and discussed one by one. And compared with other deformation methods; Finally, Co-rolling treatment was carried out. The effect of rolling on the mechanical behavior of 5052 Al-Mg alloy was studied. The main conclusions are as follows: the nanocrystalline, equiaxed and elongated sub-crystals were formed on the surface of 5052 aluminum-magnesium alloy sheet treated with RASP. Dislocation configuration mainly includes dislocation entanglement, dislocation wall, dislocation cell, and the yield strength of 5052 aluminum magnesium alloy increases with the increase of dislocation cell size. At the same time, the toughness decreases, and the yield strength reaches the maximum value of 180MPa under the condition of 50 m / s -10 min treatment, which increases the speed of 1566.RASP below 40 m / s. The increase of time will increase the microhardness curve as a whole. When the RASP velocity is 40 m / s and above, the microhardness values are intertwined in the thickness region near the surface under different time processing conditions. However, the yield strength increases linearly with the increase of RASP velocity in the depth region near the center. The uniform elongation also decreased linearly. The thickness of gradient layer changed by changing the velocity. 3) compared with room temperature RASP. The low temperature caused by liquid nitrogen plays a role in restraining dislocation movement during RASP treatment, which makes the deformation amount obtained under the same RASP parameters smaller, and the microhardness decreases as a whole along the thickness layer. However, due to precipitation strengthening, the yield strength obtained is higher. The study of different thickness of plate found that when the volume percentage of gradient layer is about 0.5, the gradient layer shows the best synergistic effect of deformation. Compared with RASP treatment, the strength of the material after Co-rolling treatment was greatly improved. However, the uniform elongation also decreased sharply, and the strength and toughness of the samples retained the gradient layer increased synchronously.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21;TG668

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