Effect of Punch Surface Grooves on Microformability of AA6063 Backward Microextrusion

Abstract

In order to apply conventional forming processes at the micro scale, the size effects caused by material properties and frictional effects must be taken into account. In this research, the effects of tool surface properties such as punch surface grooves on microextrudability, assessed using extrusion force, shape of the extrusion, and Vickers hardness, were investigated using an AA6063 billet. Microscale grooves of 5 to 10 µm were fabricated on the punch surface. The extrusion force increased rapidly as the stroke progressed for all the grooves. Comparing the product geometries showed that, the smaller the groove size, the lower the adhesion and the longer the backward extrusion length. The results of material analysis using EBSD showed that a 5 µm groove depth punch improved the material flowability and uniformly introduced more strain. On the other hand, material flowability was reduced and strain was applied nonuniformly when a mirror-finish tool was used. Therefore, the tribology between the tool and the material was controlled by changing the surface properties of the punch to improve formability.

Effect of Punch Surface Microtexture on the Microextrudability of AA6063 Micro Backward Extrusion

“…A schematic of the die and punch used for this study is shown in Figure 2 [21]. The die was divided at the center to remove the billet after extrusion.…”

“…The punch was selected for backward extrusion, and the diameter of the formed part was ϕ 1.47 mm, indicating that a bottomed microtube with a product diameter of ϕ 1.71 mm and wall thickness of 120 µm can be fabricated. A schematic of the die and punch used for this study is shown in Figure 2 [21]. The die was divided at the center to remove the billet after extrusion.…”

“…Figure 3c shows a 10 µ m-textured punch with 10 µ m grooves in Figure 3a formed using abrasive paper with a grain size of 140. Figure 3d shows a 10 µ m-textured punch with several micro-sized grooves of approximately 10 µ m A schematic of the die and punch used for this study is shown in Figure 2 [21]. The die was divided at the center to remove the billet after extrusion.…”

“…The backward extrusion of microscale parts was performed to realize microforming. When the punch surface is provided with an arbitrary surface roughness using abrasive paper, the tool contact area reduces, and material flow improves [21]. However, considerable uncertainty exists regarding the effect of the punch surface texture size on micro backward extrusion processing; therefore, the effect of the texture size from millimeter-scale to nanoscale for optimal tool surface design in microforming should be investigated.…”

Current Trends in Micro and Nano Manufacturing

“…The surface properties of the punch and die tool played an important role in the micro extrusion process due to size effects and frictional effects. On a billet AA6063, the effects of tool surface properties such as punch surface grooves on micro extrudability, assessed using extrusion force, and the shape of the extrusion and Vickers hardness were investigated [5]. The tribology between the tool and the material was controlled by introducing 5 µm deep grooves distributed by about 10 grooves per mm.…”