【作者】 蔡春波；

【导师】 吉泽升；

【作者基本信息】 哈尔滨理工大学 ， 材料学， 2009， 博士

【摘要】 用于深冲制品的铝合金板材不仅要求具有高强度,低厚度,而且要求有较低的制耳率和优良的深冲变形性能。多晶材料在塑性加工及热处理过程中产生的织构使板材产生力学性能各向异性,从而直接影响材料的制耳率和深冲性能。由于织构的存在带有普遍性,研究形变织构和再结晶织构及其所造成的材料的各向异性,对于材料的使用以及提高材料的性能有着极为重要的意义。本论文以1050铝合金板为实验材料,从理论分析和实验研究两方面入手,重点研究了1050铝合金板在热轧、冷轧及退火条件下显微组织和织构的演变规律;并研究了采用激光毛化辊轧制条件下1050铝合金的表面形貌、织构及性能的演变特征;结合实验结果,进一步研究了不同工艺参数对1050铝合金板材组织及织构的影响机理。不同轧制工艺实验结果表明:1050铝合金热轧织构以Rotated Cube-{001}<110>织构为主。随热轧变形量的增加,旋转立方织构组分减少,轧制织构组分增加。冷轧后,其织构表现出典型的“铜式”冷轧织构特征,即Cu-{112}<111>, S-{123}<634>和Bs-{110}<112>织构组分。随着冷轧变形量的增加,这些织构组分的取向密度不断增强。研究发现冷轧初始织构及冷轧道次压下量影响冷轧织构的组成。减小道次压下量有利于降低最终成品板材形变织构的强度。显微组织观察表明,在热轧样品中可观察到沿轧向伸长的变形组织,变形组织内部一些区域有亚晶粒产生;冷轧样品中纤维状组织内部形成许多位错胞,胞壁上有大量位错聚集,胞内位错密度较低,随着冷轧变形量的增加,变形组织内位错胞数量增多,尺寸减小。不同退火工艺的研究结果表明:冷轧变形量、退火温度是影响板材再结晶程度的重要因素。冷轧变形量越大,板材形变储能就越高,再结晶驱动力越大,相同温度退火后再结晶程度越高,晶粒越细小,再结晶织构组分越多。退火温度对再结晶织构有显著影响。对热轧97%、冷轧90%样品退火后,随着退火温度的升高,形变织构逐渐减弱,立方织构增强。360℃×120min退火后,再结晶基本完成,立方织构取向密度达最大,但仍有少量冷轧织构存在。退火后的力学性能随再结晶程度的变化而发生改变。回复阶段时抗拉强度由于位错密度的下降略有降低,再结晶开始后急剧下降,同时延伸率迅速增加。至完全再结晶后,两者的变化速度又开始降低。采用织构多晶体连续介质力学(CMTP)塑性理论分析了制耳与织构间的相互关系,根据不同织构的制耳倾向指数预估制耳率的大小及类型,并结合深冲实验结果,建立了深冲制耳率与织构的定量关系。结果表明:再结晶温度以下退火,样品以轧制织构为主,此时易出现45°制耳倾向,且制耳率较高。再结晶开始后立方织构和R织构逐渐增加,轧制织构与再结晶织构共存,此时易形成0°/90°和45°方向制耳,其制耳沿0°、45°、90°方向均匀分布,制耳率仅为2.5%~4%,具有较低的各向异性。完全再结晶后,退火温度继续升高,样品中形成强立方织构,易形成0°/90°制耳倾向,制耳率又开始上升。研究了激光毛化工艺对1050铝合金织构及性能的影响规律。系统分析了毛化加工参数及冷轧压下量对1050铝合金性能的影响机理。结果表明:采用激光毛化辊冷轧后,样品的冷轧织构主要包括S、Bs和Cu织构组分。再结晶退火后形成了以旋转立方取向、立方取向及随机取向为特征的再结晶织构;力学性能及深冲性能测试表明,毛化后板材的抗拉强度与普通板材接近,塑性略高于普通板材。毛化板材在不同退火温度的制耳率均低于普通板材。在360℃退火时制耳率<3%。具有最低的各向异性。更多还原

【Abstract】 Aluminum alloy sheets used in deep-drawing products need have high strength, thin sheet, little earing and excellent formability. The textures in polycrystalline material developed during thermomechanical plastic processing and heat treatment lead to the generation of anisotropy, which result to the formation of ears. Therefore, it is very important to take better account of the influence of deformation textures and recrystallization textures on anisotropy for improving performance of the sheets.In this work, the evolution of texture and microstructure in 1050 aluminum alloy sheets occurring during hot rolling, cold rolling and annealing have been studied. In addition, laser-textured process has been examined. This work involves both experimental and theoretical approach. Effects of several technological parameters on the microstructures and textures of 1050 aluminium alloy sheets are then discussed to some extent.The research results of different rolling process showed that the hot rolling textures were composed of the {001}<110> rotated cube component, as the reduction increasing, the intensity of {001}<110>rotation cubeis decreased and the rolling texture component increased. The cold rolling textures were typical Cu-type ones, i.e. consisting of mainly three texture components as Cu- {112}<111>, S- {123}<634> and Bs- {110}<112>. The orientation densities of the main texture components increased as the increasing of the cold rolling reduction. Iinitial texture before cold rolling and cold rolling reduction in pass can effect the composition of rolling texture. Results showed that increasing the number of passes in cold rolling can decrease the intensities of deformation texture. The results of OM showed that some deformed structures were formed; these structures were elongated along the rolling direction and contained some subgrains in some fields. After cold rolling, there are lots of dislocation cell formed in the fiber structures, cell-walls were composed of high density dislocation tangles around cell, and dislocation density was low within cell. As the increasing of cold rolling reduction, the number of dislocation cell increase and the size reduced.The research results of different annealing process showed that cold rolling reduction and annealing temperature were the important factors affecting the degree of recrystallization. The larger cold rolling reduction leads to the higher deformation stored energy which accordingly increased the driving force of recrystallization. Therefore, the degree of recrystallization is higher and the size of recrystallization grain is smaller after annealing at same temperature. Annealing temperature had great effect on recrystalization textures. For 97% hot rolled and 90% cold rolled sample, the intensity of cube texture was increased and the deformation texture decreased as the annealing temperature increased, recrystallization was finished on the whole after annealed at 400℃for 120min, and the orientation density of cube texture reached its maximum; but some cold rolling textures still retained. Mechanical property after annealing changed as the degree of recrystallization. The tensile strength decreased slightly at recovery stage, but reduced sharply at recrystallization stage and the elongation change reverse with tensile strength.The relationship between earing and texture is analysed based on the CMTP method (Continuum Mechanics of Textured Polycrystals). The Quantitative relationship of earing rate and texture are investigated with experimental and theoretical analysis which is the base for forcast the ears of the sheet. The results show that, the recrystallization texture mainly consisted ofβ-fiber texture at low annealing temperatures which tend to leads 45°ears. After recrystallization begin, the recrystallization cube and R texture increase, the rolling texture and recrystallization texture coexist in the specimen which is apt to leads 0°/90°and 45°ears, the earing rate is low. After complete recrystallization, the high intensity of cube texture is developed, which leads to high 0°/90°ears and the earing rate is increased again. The influence of laser-textured process on the texture and performance of 1050 aluminum alloy is investigated and analyzed systematically. Experimental results show that the sheets deformed with laser-textured roll developed the typical rolling textures, which consist of Bs, Cu and S components. After annealing, the specimen shows a substantially different recrystallization texture compared with conventional sheet, which comprising only a weak cube-orientation and rotated-cube orientation as well as a much higher fraction of randomly orientation. The results of mechanical property show that the tensile strength of the textured sheet is approach to that of conventional sheet, but the plastic is slightly higher. The deep drawing test result show that the earing rate of the textured sheets after annealed at different temperature is all lower than the conventional sheets. After annealed at 360℃, the earing rate is less than 3%, which get the lowest anisotropy.更多还原