Influence of microstructure on surface integrity in turning—part I: the influence of the size of the soft phase in a microstructure on surface-roughness formation

Abstract

The paper deals with influences of fine-turning conditions on the state of a surface and a surface layer from the viewpoint of the size of the soft phase in the microstructure of aluminium-silicon alloys. In the selection of the alloy, a criterion of microstructure was taken into account, which included the aluminium-base soft phase and the brittle phase represented by silicon. A reference surface was prepared prior to fine turning by the electrochemical removal. In spite of very similar mechanical properties, the aluminium alloys chosen show very different behaviour when it comes to the formation of a new surface in the cutting zone. The surface quality after fine turning is described by measurement of roughness. With the criterion of microstructure, average intercept lengths measured at the aluminium-base soft phase were taken into account. The results of measurements of the mean intercept length of the soft phase and of the surface roughness after fine turning were analysed using the theory of specimen recognition. The method chosen confirmed the direct relationship between the size of the soft phase and the roughness of the surface formed after fine turning.