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| 镁锂合金微型热管电场辅助超塑挤压成形 |
| Electric Field Assisted Superplastic Extrusion Forming of Mg-Li Alloy Micro Heat Pipe |
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| DOI：10.3969/j.issn.1674-6457.2023.07.002 |
| 中文关键词: 微型热管 镁锂合金 电致超塑性 电场辅助超塑挤压 尺寸效应 |
| 英文关键词: micro heat pipe Mg-Li alloy electro super-plasticity electric field assisted superplastic extrusion size effect |
| 基金项目:北京市自然科学基金（3222014） |
| Author Name | Affiliation | | MENG Bao | School of Mechanical Engineering, Beihang University, Beijing 100191, China | | YANG Jian-qiang | School of Mechanical Engineering, Beihang University, Beijing 100191, China | | PAN Feng | School of Mechanical Engineering, Beihang University, Beijing 100191, China | | WAN Min | School of Mechanical Engineering, Beihang University, Beijing 100191, China |
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| 中文摘要: |
| 目的 解决新一代轻质镁锂合金微型热管加工难度大、尺寸精度差、性能不稳定的难题。方法 对镁锂合金坯料施加脉冲电流，利用脉冲电流产生的电致超塑性效应提高塑性变形能力，降低镁锂合金微型热管的加工难度。利用有限元仿真和实验相结合的方法，分析微型热管电场辅助超塑挤压过程中微型热管的变形行为与缺陷演变。结果 电场辅助超塑成形的挤压力远低于相同温度下纯加热成形的变形力，能够单道次挤压出Φ2 mm的微细热管。结论 与相同温度下的纯加热成形相比，电场辅助微型热管超塑挤压成形的变形抗力降低了50%，证明电致超塑性可有效降低镁锂合金微型热管的加工难度。随着超塑挤压速度的增加，变形不均匀性加剧。当挤压速度为0.006~0.02 mm/s时，能够获得尺寸精度和表面质量较好的微型齿槽。当挤压速度超过0.02 mm/s时，容易导致微型齿与管壁区域之间的材料流动不均匀，甚至诱发断裂。当挤压温度为200~280 ℃时，可以软化材料，降低挤压力，避免了温度过高产生的“焊接”现象。镁锂合金微型热管成形过程受尺寸效应影响，在挤压杆微型齿槽表面，亚毫米尺寸导致镁锂合金与模具间的界面摩擦增大、材料流动变慢，进而影响了微型齿槽的填充质量。 |
| 英文摘要: |
| The work aims to solve the problems of difficult processing, poor dimensional accuracy and unstable performance of the new generation of lightweight Mg-Li alloy micro heat pipes. Pulse current was applied to the Mg-Li alloy blank. The electro super-plasticity effect generated by the pulse current was used to improve the plastic deformation ability and reduce the processing difficulty of Mg-Li alloy micro heat pipes. The finite element simulation was combined with experiment to analyze the deformation behavior and defect evolution of micro heat pipes during electric field assisted superplastic extrusion. The extrusion force of electric field assisted superplastic forming was much lower than that of heating forming at the same temperature, which could realize the extrusion of Φ2 mm micro heat pipes in a single pass. The deformation resistance of electric field assisted micro heat pipe superplastic extrusion is reduced by 50% compared with heating forming at the same temperature, which proves that electro super-plasticity can effectively reduce the processing difficulty of Mg-Li alloy micro heat pipes. What’s more, with the increase of superplastic extrusion speed, the deformation inhomogeneity intensifies. At the extrusion speed of 0.006-0.02 mm/s, micro cogging with good dimensional accuracy and surface quality can be obtained. When the extrusion speed exceeds 0.02 mm/s, it is easy to cause uneven material flow between the micro gear and the pipe wall area, and even induce fracture. The extrusion temperature of 200-280 ℃ can soften the material, reduce the extrusion force, and avoid the "welding" phenomenon caused by excessive temperature. In addition, the forming process of Mg-Li alloy micro heat pipes is affected by the size effect, and on the surface of the micro cogging of the extrusion rod, the interface friction between the Mg-Li alloy and the mold increases due to the submillimeter size, resulting in slower material flow, which in turn affects the filling quality of the micro cogging. |
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