多道次ECAP的模具设计及实验研究

Multi-pass ECAP mold design and experimental research

为了研究多道次等径角挤压(ECAP)工艺制备超细晶材料,以解决传统ECAP模具存在的飞边和装拆困难等问题,提出了一种对称分模自由套模具的设计方案。该方案是将凹模模芯设计成对称拼块式并通过凹模座进行预紧;凹模座内表面与凹模外表面均采用锥面的设计,当受到挤压时,凹模的闭合会愈来愈紧而不易产生飞边,拆卸时只需将模具倒扣反压即可轻松脱模。同时,基于虚拟设计技术优化了模具的结构和工艺参数,进行了ECAP制样及相关实验的研究。研究结果表明,模具设计方案有效防止飞边产生,实验效果较好。金相显微组织观察表明,随着挤压道次的增加,平均晶粒尺寸逐渐减小。显微硬度分析表明,随着挤压道次的增加,试样的硬度有大幅度的提高。

In order to investigate the influence of multi-pass equal channel angular pressing（ECAP） on the grain refinement and to solve the problem of mold flash and disassembling difficulties, a new mold called symmestrical-split combined die is designed. In the solution, the concave die has been symmetrically divided into two parts and confined to die holder. The inner surface of die holder and the outer surface of the concave die were designed as conical surface, therefore concave die will be closed more tightly in the extrusion process and can get rid of mold flash, and the mold structure can be disassembled easily. Basing on the virtual design technology, mold design and related parameters are determined, the optimized parameters of structure and processing are decided. The result shows that the mold design can effectively prevent the mold flash, and the experiment result is good. Metallography indicates that the average grain size has decreased by increasing extrusion passes. Microhardness shows that the hardness of the samples has been improved sharply by increasing extrusion passes.