Observation of Cutting Deformation Zone of Directionally Solidified Ag-Cu Eutectic Alloy

Abstract

This paper describes the cutting mechanism of directionally solidified Ag-Cu eutectic alloy. The eutectic alloy has two prefered orientations, i.e. (113)[1\bar10] and (111)[1\bar10]. {113} and {111} planes are parallel with the side plane of the workpiece and a ⟨110⟩ axis is parallel with the direction of solidification. The experiment is conducted under orthogonal cutting. The inside of chip and the shear zone which are considered approximataly to be the plane-strain condition are observed by optical microscope and SEM, and also the relation between the texture and the cutting mechanism is investigated.
The main results obtained are as follows.
(1) In applying the tool rake angle of 40 deg., the cutting process is stable and a continuous ribon-like chip is formed. However, the shear angle shows the periodic change slightly. Consequently the streamline makes chevron-type markings and the free surface of chip is uneven.
(2) In applying the tool rake angle of 30 deg., chevrons of streamlines become acute. In this case the cutting mechanism transforms from the shear plane to the shear zone model. Reducing the tool rake angle to 20 or 10 deg., shear deformation becomes discontinuous and the cutting mechanism tends to become the shear type model.
(3) In cutting the workpiece having the texture with the rake angle of 40 deg., the cutting process is stable, and there is good agreement between the observed shear angle and the estimated one based on the assumption that shear deformation occurs in the slip system {111}⟨110⟩.