电流辅助铝合金板材拉深成形规律研究

发布时间：2018-05-23 22:45

本文选题：2024铝合金 + 筒形件拉深　；参考：《南京航空航天大学》2017年硕士论文

【摘要】：铝合金由于质量轻、节能等优点在工业中得到广泛运用,但室温下低塑性和高温成形下零件表面质量差等缺点制约了铝合金的发展。而研究表明电流辅助成形(电致塑性)可在较低温度下使材料塑性提高,故本文对电流辅助作用下的AL-(3.8-4.9)Cu-(1.2-1.8)Mg铝合金板力学性能以及筒形件拉深成形进行了一定程度的研究。首先通过分别在未通电室温下、高频(25-100hz)及低频(0-0.5hz)电流辅助作用下单轴拉伸实验,研究了板材的力学性能,并对高频作用下曲线进行拟合得到本构方程;通过热电耦合有限元模拟分析了材料在单拉过程中电场和温度场的分布、筒形件拉深工艺中的电场和温度场分布以得到优化的电极接入方式;结合模拟仿真结果设计并进行了未通电室温下、“压边圈—凹模”通电下、“凸模—凹模”通电下的筒形件拉深实验;通过光学组织观察、SEM断口分析研究了不同电参数作用下材料微观组织演化过程。研究结果表明:高频脉冲电流辅助条件下,材料随着电流密度、电流频率以及电流脉宽的增加,材料的延伸率、流变应力减小;并通过耦合电参数的J-C修正模型拟合的本构关系平均误差在5%以内。低频脉冲电流辅助条件下,材料在50A/mm2的电流预处理后或者90A/mm2的电流预处理后时效24小时,延伸率较室温下有17.6%的提升;在无预变形条件下,材料延伸率、强度随着电流密度增加而减小;在有预变形条件下,电流密度为110 A/mm2、150 A/mm2材料延伸率较无电流拉伸分别提高了29.4%、47.6%。“压边圈—凹模”通电拉深将拉深高度提高了近134%,而凸模—凹模通电拉深却难以拉深成形。150 A/mm2脉冲电流作用下,材料在153度就发生了动态再结晶,通电拉深所得筒形件的凸模圆角区域、凹模圆角区域的晶粒较室温下有明显减小,且发生了动态再结晶。
[Abstract]:Aluminum alloy is widely used in industry because of its advantages of light weight and energy saving. However, the development of aluminum alloy is restricted by the shortcomings of low plasticity at room temperature and poor surface quality of parts under high temperature forming. The results show that the plastic properties of AL-(3.8-4.9)Cu-(1.2-1.8)Mg aluminum alloy sheet under the condition of current assisted forming (EPS) can be improved at lower temperature, so the mechanical properties of the AL-(3.8-4.9)Cu-(1.2-1.8)Mg aluminum alloy sheet and the deep drawing of the cylindrical part are studied to a certain extent in this paper. At first, the mechanical properties of the plate were studied by the order axis tensile experiment under the condition of unelectrified room temperature, high frequency (25 ~ 100hz) and low frequency (0 ~ 0.5hz) electric current. The constitutive equation was obtained by fitting the curve under the high frequency action. The distribution of electric field and temperature field in single drawing process and the distribution of electric field and temperature field in cylindrical drawing process were analyzed by thermoelectric coupling finite element simulation. Based on the simulation results, the experiments of drawing the cylindrical parts under the current of "blank holder ring-die" and "convex die" at room temperature without electrification are carried out. The microstructure evolution process of materials under different electrical parameters was studied by SEM fracture analysis. The results show that with the increase of current density, current frequency and current pulse width, the elongation and flow stress of the material decrease with the increase of current density, current frequency and current pulse width. The average error of constitutive relation fitted by J-C modified model with coupled electrical parameters is less than 5%. Under the condition of low frequency pulse current assisted, the elongation of the material aged 24 hours after the current pretreatment of 50A/mm2 or the current pretreatment of 90A/mm2 was 17.6% higher than that at room temperature, and the elongation of the material without predeformation was 17.6% higher than that at room temperature. The tensile strength decreases with the increase of the current density, and the elongation of the material with current density of 110 A/mm2150 A/mm2 is increased by 29.4% and 47.6%, respectively, compared with that of the non-current tension under the condition of pre-deformation. The "blank holder ring-die" electric drawing raised the drawing height by nearly 134k.However, when the protrusion-die electrified drawing was difficult to draw deeply, the material was dynamically recrystallized at 153C under the action of the pulse current of .150. The grains in the corner region of the convex die and the corner region of the die are obviously smaller than those at room temperature, and dynamic recrystallization occurs.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG389

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