Investigation on the mechanism of micro-milling CoCrFeNiAlX high entropy alloys with end milling cutters

Abstract

This paper aims to explore the influence mechanism of different Al contents on the mechanism of CoCrFeNiAlX high entropy alloy micro-milling by studying CoCrFeNi (Al0), CoCrFeNiAl0.6 (Al0.6) and CoCrFeNiAl (Al1). The law of changes in the temperature field, cutting force, residual stress, and surface roughness of Al0, Al0.6 and Al1 is investigated by the simulation method. The research results showed that the chips produced during the milling of three workpieces with different Al contents are different in the milling process. In particular, those produced by Al0 are shaped like long flakes and easy to adhere to the milling part, thus leading to short-duration chip accumulation. This is also the reason why the milling temperature of Al0 is obviously higher than that of Al0.6. The milling temperature of each workpiece gradually increases with the increase in milling speed, reaching the maximum when the milling speed reaches 450 mm/s. At the same milling speed, the milling temperature of each workpiece is sequenced as follows: Al1>Al0>Al0.6. Also, the milling temperature of the three types of workpieces shows an upward trend within a complete milling cycle, with the maximum milling temperature being far lower than that of traditional milling. With the increase in milling speed, the changes in the cutting forces of Y and Z directions are virtually the same for the three types of workpieces with different Al contents. However, the influence of milling speed on X-direction cutting force is relatively complex. The X-direction cutting force of Al1 and Al0 changes little, almost forming a horizontal line, while that of Al0.6 tends to increase first and then decrease. With the increase in milling speed, all the three-way cutting forces of three types of workpieces increase. With the increase in the feed rate, for each workpiece with three different Al contents, the X-direction cutting force first rises and then falls; the Z-direction cutting force tends to decrease gradually and the Y-direction cutting force almost forms a horizontal line. Also, the cutting force of Al0.6 is the smallest among the three under the same parameter and its peak value in the X direction is 68% of that of Al1 and 93% of that of Al0. With the increase in milling speed and milling depth, the changes of the residual stress for the workpieces with three different Al contents tend to be “spoon” shaped and the peak value of the residual stress for each workpiece is sequenced as follows: Al1>Al0.6>Al0. Among them, the peak value of residual stress for Al0.6 is 57% of that of Al0. The machined surface roughness of Al0.6 is the smallest after the whole micro-milling process is completed for the three types of workpieces with different Al contents.