Enhancing the formability of surface-arrayed microchannels in pure titanium UTFHP wicks using electrically assisted micro-rolling

The ultra-thin flat heat pipe (UTFHP) wick with an arrayed microchannel structure represents an ideal choice for next-generation spacecraft in extreme thermal management applications. It is challenging to achieve efficient, high-precision, and low-cost arrayed microchannel processing using conventional manufacturing techniques. The electrically assisted micro-rolling (EAMR) technology proposed in this study demonstrates significant advantages in the fabrication of array microchannels on pure titanium sheets. At the outset, EAMR experiments were performed at varying current densities using the developed equipment. Subsequently, the effects of current density on microchannel surface quality, filling behavior, and microstructural evolution in the filling zone were examined, thereby revealing the mechanism behind the enhanced filling performance. The results show that higher applied current densities sharply define the edges of microchannel valleys and ridges, with filling capacity increasing as current density rises. The microchannels exhibited a uniform structure, straightness, and no significant defects. The applied current density markedly increased filling height while substantially improving microchannel uniformity and symmetry, with filling performance at rounded corners gradually improving. Electron backscatter diffraction (EBSD) analysis revealed that the average grain size in the filling zone was significantly smaller than that in the initial sheets. As the current density increased, the coordinated deformation capability between grains improved, the proportion of twins decreased markedly, and dislocation slip characteristics gradually became more pronounced. Pronounced dynamic recovery occurred, with grain sizes in various regions gradually growing. In the filling zone of pure titanium, the Schmid factor (SF) of non-base plane slip markedly increased, while the slip capacity of pyramidal and prismatic slip was enhanced. Non-base plane texture gradually became dominant, with corresponding non-base plane slip emerging as the primary deformation mode in pure titanium. This study provides experimental and theoretical foundations for the efficient manufacture and application of water-filled titanium UTFHP wicks.