超细晶AZ31镁合金微压印成形工艺研究

发布时间：2018-06-23 00:46

本文选题：高压扭转(HPT) + 超细晶　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：微压印成形工艺制备微通道具有稳定性好、成本相对较低、适合大批量生产等优势,而晶粒尺寸对微通道成形过程影响显著,粗晶材料无法保证微通道的尺寸精度。通过剧烈塑性变形技术制备的超细晶材料具有更好的成形性能,是用于制造微型构件的理想材料。本文对高压扭转(High pressure tortion,HPT)方法获得的不同晶粒尺寸的超细晶(Urtalfine-grained,UFG)AZ31镁合金进行显微硬度测试、微观组织观察、微拉伸性能测试、微拉伸试样断口观察、V型槽微压印填充实验及其有限元模拟,得到并分析了室温下不同圈数HPT处理的AZ31镁合金试样的硬度分布、微拉伸曲线和显微组织。随后进行了包括V型单槽和U型槽阵列微通道微压印试验,分析了V形槽槽宽、成形温度对单槽压印填充过程和填充质量的影响规律,以及在最佳成形温度和压力下超细晶AZ31镁合金的阵列微通道填充性能,实现了阵列微通道高质量、高精度的成形。温度为423K和43K的情况下,随着HPT圈数的增加,试样的延伸率变大屈服强度变小。温度为523K时,除原始试样屈服强度较高外,其余试样的屈服强度都较低且几乎相同,所有试样的延伸率都分布在200%左右。对于10T的试样在423K至523K进行拉伸时,随着应变速率从1.0×10-1s-1减小到1.0×10-4s-1,试样的延伸率增大,屈服强度降低,应变速率为1×10-4s-1时延伸率达到400%,具有超塑性。423K进行拉伸时,除10T试样在523K时断口微坑为拉长形外,其余试样断口微坑为等轴状。1/4T试样的断口微坑最大,之后随着HPT处理圈数的增多,断口微坑减小。粗晶和超细晶AZ31镁合金V槽压印和阵列通道微压印实验表明,经HPT处理的材料在成形过程中,因晶粒细小,屈服应力低,其填充性能较原始材料得到了显著提高,填充率较高,并且随着HPT扭转圈数的增加而增加。随着槽宽的增大,材料的阵列微通道填充质量变好,通道高度增加。经HPT处理的材料成形出的阵列微通道表面质量与原始材料相比显著增加,且表面成形质量随着HPT扭转圈数的增加而增加。通过对成形压力和温度的实验研究,确定了AZ31镁合金阵列微通道微压印成形工艺的最佳参数:成形压力为4KN,成形温度为473K。实验结果表面,在此成形条件下,除原始AZ31镁合金外,其余材料的微通道的填充率均为100%。这一结果与单槽压印实验一致,即经HPT处理的材料成形出的微通道表面质量比原始试样好,且随着HPT处理圈数的增加,表面质量越来越好。经过HPT处理的材料,具有较好的尺寸精度与重复精度,微通道侧壁垂直度较好,顶部平坦,截面形状规则。阵列微通道压印过程中出现了墩粗现象:试样边缘处的微通道外侧的填充高度大于内侧,材料填充不均匀。
[Abstract]:The microchannel prepared by micro-imprint process has the advantages of good stability, relatively low cost and suitable for mass production. However, the grain size has a significant effect on the forming process of microchannel, and the size accuracy of microchannel can not be guaranteed by coarse grain material. The ultrafine grained material prepared by severe plastic deformation has better formability and is an ideal material for the fabrication of micro components. In this paper, the microhardness, microstructure and tensile properties of ultrafine grained AZ31 magnesium alloy with different grain sizes obtained by high pressure torsion method were investigated. The fracture surface of the microtensile specimen, the filling test of V-shaped groove and its finite element simulation were observed. The hardness distribution, microtensile curve and microstructure of AZ31 magnesium alloy treated with HPT at room temperature were obtained and analyzed. Then, the microchannel microembossing tests including V-groove and U-groove array were carried out, and the influence of V-groove width and forming temperature on the filling process and filling quality of single groove was analyzed. At the optimum forming temperature and pressure, the array microchannel filling performance of ultra-fine grain AZ31 magnesium alloy is achieved. The high quality and high precision forming of the array microchannel is realized. When the temperature is 423K and 43K, with the increase of the number of HPT cycles, the elongation of the specimen increases and the yield strength decreases. When the temperature is 523K, the yield strength of the other specimens is lower and almost the same, except for the higher yield strength of the original specimen, and the elongation of all the specimens is about 200%. When the strain rate of 10T specimen decreases from 1.0 脳 10-1s-1 to 1.0 脳 10-4s-1 at 423K to 523K, the elongation of the specimen increases and the yield strength decreases. When the strain rate is 1 脳 10-4s-1, the elongation reaches 400, and the strain rate reaches 400 when the strain rate is 1 脳 10-4s-1, and when the strain rate decreases from 1.0 脳 10-1s-1 to 1.0 脳 10-4s-1, when the strain rate is 1 脳 10-4s-1, Except for 10T specimens with elongated fracture pits at 523K, the fracture micropits of the other specimens were the largest in equiaxed. 1 / 4T specimens, and then decreased with the increase of HPT treatment cycles. The experiments of V-groove embossing and array channel microlithography of coarse and ultrafine AZ31 magnesium alloys show that the filling properties of the materials treated with HPT are significantly improved and the filling rate is higher than that of the original materials due to the small grain size and low yield stress during the forming process. And with the increase of the number of HPT torsional cycles, it increases. With the increase of the slot width, the filling quality of the array microchannels becomes better and the channel height increases. The surface quality of the array microchannel formed by HPT treatment is significantly higher than that of the original material, and the surface forming quality increases with the increase of the number of HPT torsion cycles. Through the experimental study on the forming pressure and temperature, the optimum parameters of the microchannel microembossing process of AZ31 magnesium alloy array were determined: the forming pressure was 4KN and the forming temperature was 473K. The experimental results show that the filling ratio of the microchannels of the other materials except the original AZ31 magnesium alloy is 100% under this forming condition. The results are in agreement with the single-channel imprint experiment, that is, the surface quality of the microchannel formed by HPT treatment is better than that of the original sample, and with the increase of the number of cycles of HPT treatment, the surface quality is getting better and better. The material treated by HPT has better dimensional accuracy and repetition accuracy, better perpendicularity of the side wall of microchannel, flat top and regular section shape. In the process of array microchannel imprint, the diameter of the piers appears: the filling height of the outside of the microchannel at the edge of the sample is higher than that of the inside, and the filling of the material is not uniform.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG306

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