Enhancing surface integrity by high-speed extrusion machining

Abstract

High-speed machining (HSM) is an advanced machining technology to form components. However, the poor surface integrity tends to appear due to chip flow instability in HSM. It is found that the surface integrity results from the competition of shear deformation instability between in primary shear zone (PSZ) and in separating shear zone (SSZ). To improve the surface integrity of machined components, the systematic high-speed extrusion machining (HSEM) experiments of magnesium alloy AZ31B with different constraint extrusion factors (CEFs) were carried out. The instability of shear deformation in PSZ is suppressed, and the microwaves on machined surface disappear when CEF is equal to or larger than a certain value. The measurements of the machined surface show that an improvement of surface integrity is achieved if CEF exceeds a certain value. The theoretical model for HSEM was established to elucidate the critical CEF. The underlying physics of surface integrity in HSEM is further revealed. The experimental results verify the validity of the theoretical model.