Micro-extrusion process and microstructure evolution of miniature heat pipe in 6063 aluminum alloy

Micro-extrusion process of miniature heat pipe with axial micro grooves is particularly difficult due to ultra-large extrusion ratio and complex cross-sectional shape. In this study, the shape control of a miniature heat pipe in 6063 aluminum alloy with boundary dimension of 5×4 mm has been successfully realized during micro-extrusion. Micro-extrusion process and microstructure evolution of the miniature heat pipe were investigated by the combination of finite element (FE) analysis with experiments. The results show that material flow deformation behavior during micro-extrusion is highly affected by size effect, and lower ram speed is conductive to forming integrity, dimension accuracy and surface quality of the heat pipe profile. The primary mechanism for micro-extrusion failure of micro-grooves is severely more uneven material flow between the micro rib and base region at higher ram speed, which is caused by size effect and results in shear deformation and even fractures of micro rib. Further research shows that, compared to the extrusion using as-cast billets, much coarser grains were obtained after micro-extrusion using as-extruded billets at an ultra-large extrusion ratio of 205. Besides that, the entirely different texture components after extrusion were obtained instead of the typical < 100 > //ED or < 111 > //ED fiber texture components. These atypical texture components can be regarded as texture deviating from ideal texture by a certain angle (15° or 20°) along φ axis or φ1 axis.