【摘要】：攪拌摩擦加工可以細化材料的晶粒,提高材料的力學性能,塑性也會有明顯的增加。本文首先開展單道次攪拌摩擦加工實驗,采用正交試驗法選取最具代表性的攪拌頭旋轉速度、進給速度、軸肩下壓量工藝參數(shù)組,對5mm厚的5083鋁合金進行攪拌摩擦加工。對加工試樣進行拉伸試驗、金相試驗、硬度試驗和斷口分析,研究各參數(shù)下攪拌區(qū)域的組織和性能情況,得到最優(yōu)的攪拌摩擦加工工藝參數(shù)。然后使用得到的工藝參數(shù)對5083鋁合金進行多道次攪拌摩擦加工。多道次攪拌摩擦加工將研究最優(yōu)的攪拌頭平移距離,從而制備大面積晶粒細化的5083鋁合金材料;研究溫度、攪拌頭形狀對材料晶粒尺寸的影響并嘗試了用板材堆疊的方法來制備大厚度的細晶材料。對多道次攪拌摩擦加工得到的大面積細晶5083鋁合金進行高溫拉伸試驗,研究其細晶超塑性性能。使用ABAQUS有限元軟件分別模擬超塑性板材和普通板材的擠壓、沖壓成形。本論文的具體研究結果如下:(1)獲得了單道次加工的最優(yōu)工藝參數(shù)。當攪拌頭轉速為1300r/min、進給速度為400mm/min、下壓量為0.3mm時,經過加工的試樣表面無宏觀缺陷。試樣的抗拉強度為214MPa,達到母材的93.05%;屈服強度為112.4MPa;斷后延伸率為18.37%。5083鋁合金材料在經過攪拌摩擦加工后,攪拌區(qū)域的晶粒被打碎,由原本沿軋制方向被拉長的粗大晶粒變成細小的等軸晶粒。攪拌摩擦加工后攪拌區(qū)域的硬度小于母材區(qū),出現(xiàn)一段尺寸與攪拌針尺寸基本吻合的軟化區(qū)。(2)多道次攪拌摩擦加工方面。最優(yōu)道次間隔與攪拌針端部直徑相同。因攪拌頭軸肩與板材的接觸面積要比攪拌針表面積大,摩擦產生的熱量也較多,從而導致上部區(qū)域的晶粒在高溫下長大,尺寸大于下部區(qū)域。在攪拌摩擦加工過程中進行加水冷卻可以降低上部區(qū)域的溫度,從而減小上部區(qū)域的晶粒尺寸。相比于圓錐形攪拌頭,在使用圓柱形攪拌頭進行加工時,晶粒更加粗大,不利于細晶材料的制備。使用堆疊多道次攪拌摩擦加工的方法,可以制備大厚度晶粒細化的5083鋁合金材料。(3)超塑性成形方面。高溫拉伸試驗表明:在應變速率為3×10-3/s,溫度為530°C時,經過加工試樣的延伸率最大,達到216%;而未經過加工的試樣在相同應變速率和溫度下延伸率僅為83%。細晶超塑性5083鋁合金在成形時塑性和金屬流動性更好,有限元仿真分析表明,超塑性成形時所需對凸模施加的壓力更小。
[Abstract]:Friction stir processing can refine the grain size of the material, improve the mechanical properties of the material, and increase the plasticity obviously. In this paper, the single pass friction stir experiment was carried out, and the most representative process parameters of rotating speed, feed speed and axial shoulder pressure were selected by orthogonal test. The 5083 aluminum alloy with 5mm thickness was processed by friction stir. The tensile test, metallographic test, hardness test and fracture analysis were carried out to study the microstructure and properties of the stir region under various parameters, and the optimum technological parameters of friction stir processing were obtained. Then the 5083 aluminum alloy was processed by multi-pass friction stir with the obtained process parameters. Multi-pass friction stir processing will study the optimal translational distance of the stir head, so that the 5083 aluminum alloy material with large area grain refinement will be prepared, and the temperature will be studied. The effect of mixing head shape on the grain size of the material was studied and the method of plate stacking was used to prepare the fine grain material with large thickness. The high temperature tensile test of large area fine grain 5083 aluminum alloy obtained by multi-pass friction stir processing was carried out and the superplasticity of fine grain was studied. The ABAQUS finite element software is used to simulate the extrusion and stamping of superplastic sheet and common sheet respectively. The results of this paper are as follows: (1) the optimal process parameters of single pass machining are obtained. When the speed of the mixing head is 1 300 r / min, the feed speed is 400 mm / min and the pressure is 0.3mm, the surface of the processed sample has no macroscopic defects. The tensile strength of the sample is 214MPa, which reaches 93.05 of the base metal, the yield strength is 112.4MPa, and the elongation after breaking is 18.37.5083 aluminum alloy material, after friction stirring, the grains in the stirring region are broken. The coarse grains which were originally elongated along the rolling direction were changed into fine equiaxed grains. The hardness of the stir region is smaller than that of the base metal area after friction stir processing, and there is a softening zone in which the size of the stir needle basically coincides with the size of the stir needle. (2) the multi-pass friction stir processing. The optimal interval is the same as the diameter of the end of the stirring needle. Because the contact area between the shaft shoulder and the plate is larger than that of the agitator needle and the heat produced by friction is more than that of the stirring needle the grain in the upper region grows at high temperature and the size is larger than that in the lower part. Water cooling during friction stir processing can reduce the temperature of the upper region and decrease the grain size of the upper region. Compared with the conical mixing head, the grain size is thicker when the cylindrical stirring head is used, which is not conducive to the preparation of fine crystal material. 5083 aluminum alloy materials with large thickness grain refinement can be prepared by stacking multi-pass friction stir processing. (3) superplastic forming. The results of high temperature tensile test show that the maximum elongation of the processed sample is 2166C at the strain rate of 3 脳 10 ~ (-3) / s and the temperature of 530 擄C, while the elongation of the unmachined sample is only 833 at the same strain rate and temperature. The finite-grain superplastic 5083 aluminum alloy has better plasticity and metal fluidity during forming. The finite element simulation analysis shows that the pressure applied to the punch is lower during superplastic forming.
【學位授予單位】：浙江理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG146.21;TG453.9

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