Research On Design And Wettability Of Multiscale Microstructures On Aluminum Alloy

Single-scale and multi-scale microstructures are the main reasons for the realization of super-hydrophobic surface for natural organism.Therefore,single-scale microstructure was fabricated on the surface of aluminum alloy by using the micro-milling technology,and multi-scale microstructure was fabricated by using complex machining of micro-milling technology and wire cut electrical discharge machining(WEDM)in this paper.The influence of machining parameters of different processing methods on the morphology and size of the surface microstructure were studied.The effect of microstructure size on wettability was studied,and the hydrophobic stability was analyzed.The main research contents and conclusions are as follows.1.The multi-scale microstructures of groove and square array were designed based on the hydrophobic microstructure of biological surface,and the influence law of size parameters on hydrophobic performance was analyzed by using energy method.The results show that the hydrophobic characteristics of the secondary micro-nano structure are very important for the realization of super-hydrophobic surface,and the h value of the primary structure can improve the stability of the water drop when in the contact state of Cassie-Baxter model.Orthogonal test method was adopted to optimize the processing parameters of saw blade milling cutter.The optimal cutting parameters were that the spindle speed n=2000r/min,feeding speed =500mm/min,cutting depth =30?m.2.The change of surface wettability from hydrophilic to hydrophobic was realized through the single-scale microstructure on the surface of aluminum alloy.The contact angle of the groove array was effectively improved from 50° up to 143.27° in the vertical direction,and 110.25° in the parallel direction.The maximum contact angle of the square array was 121.09°.Meanwhile,the water droplets exhibit strong adhesion on the surface of single-scale microstructure.The surface wettability was transformed from hydrophobic to super-hydrophobic by the multi-scale microstructure,and the adhesion of water droplet was reduced on the surface of aluminum alloy.3.Mechanism analysis showed that the increase of surface roughness is the key factor to change the wettability for single-scale microstructure,and super-hydrophobic performance was realized mainly depending on multi-scale structure effect for multi-scale structure.The contact state between water droplets and micron grade crater structure is Wenzel model,and the contact state of nano-scale structure is Cassie-Baxter model.The contact state of the primary structure is in a transitional state from the Cassie-Baxter wetting model to Wenzel wetting model.4.The stability test results show that the surface of aluminum alloy after composite processing has good environmental adaptability and certain mechanical stability.