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

Micro-extrusion process of miniature heat pipe (MHP) 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 6063 aluminum alloy MHP fabricated by micro-extrusion was successfully overcome, and the microstructure evolution in micro-extrusion using as-extruded billets was studied. The results obtained by finite element (FE) analysis and experiments show that the material flow deformation behavior in micro-extrusion is highly affected by size effect, and lower ram speed is conductive to forming integrity, dimension accuracy, and surface quality of extruded MHP profiles. The primary mechanism for the 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 ribs. 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 micro-extrusion were obtained instead of the typical < 100 > //the extrusion direction (ED) or < 111 > //ED fiber texture components. These atypical texture components can be regarded as the texture deviating from ideal texture by a certain angle (15 degrees or 20 degrees) along phi axis or phi(1) axis.

Automated summary

In this study, the shape control of a micro-extruded aluminum alloy MHP was successfully achieved. The effects of size on material flow deformation behavior in micro-extrusion were investigated, and it was found that lower ram speed is beneficial for forming integrity and surface quality of the extruded profiles. The failure mechanism for micro-grooves during micro-extrusion was attributed to uneven material flow caused by size effect. The microstructure analysis revealed that using as-extruded billets in micro-extrusion resulted in coarser grains and different texture components compared to using as-cast billets.