2A12铝合金锥形曲面件超低温成形工艺研究

Investigation of Cryogenic Forming for 2A12 AluminumAlloy Conical Part

为解决铝合金锥形件常温成形起皱与开裂并存的难题,利用超低温增塑增强的双增效应,提出了铝合金锥形曲面件梯度超低温成形工艺。以直径300 mm的2A12铝合金锥形曲面件为研究对象,通过数值模拟和工艺实验,阐明不同锥度曲面件拉深变形过程的应力、应变和壁厚分布规律。结果表明,在液氮温度条件下,2A12-O铝合金延伸率相对常温可以提高92.1%、硬化指数提高29.2%,具有显著的“双增效应”。随着试件锥度增大,抑制起皱所需的最小压边力先增大后减小,等效应变最大区域由凹模圆角向凸模圆角转移,凸模圆角处发生集中变形,壁厚减薄严重。采用梯度超低温可以抑制凸模圆角区的集中变形,进而可以提高压边力来防止起皱,成功试制出锥形曲面试件,相对常温成形高度提高了132.9%。本文的研究可为铝合金深腔锥形曲面件一次性高性能精密成形提供理论指导。

To avoid the occurrence of wrinkling and splitting in the forming of aluminum alloy conical parts at room temperature,the cryogenic forming process for aluminum alloy conical parts is proposed according to the“dual enhancement effect”of enhancement ductility and hardening ability at cryogenic temperature.The 2A12 aluminum alloy conical part with a diameter of 300 mm was studied through numerical simulation and process experiments and the laws of the distribution of stress,strain,and wall thickness distribution during the deep drawing process of conical curved parts with different conical angles were clarified.Under liquid nitrogen temperature conditions,the elongation of the 2A12-O aluminum alloy increased by 92.1% and the hardening index increased by 29.2% compared to room temperature,showing a significant“dual enhancement effect”.As the angle of the conical part increased,the minimum blank holding force preventing wrinkling increased and then decreased.The large deformation area transferred from the die corner to the punch corner of the part and concentrated deformation occurred at the punch corner area causing severe thinning of wall thickness.The concentrated deformation in the punch corner area was suppressed under the gradient ultra-low temperature,thereby the wrinkling can be prevented by increasing the blank holding force.A conical curved part was successfully produced and the forming height increased by 132.9% compared to the condition of room temperature.The study can provide theoretical guidance for the one-time high-performance precision forming of aluminum alloy deep cavity conical curved parts.