Surface integrity in wire-EDM tangential turning of in situ hybrid metal matrix composite A359/B4C/Al2O3

Abstract

In this work, wire electric discharge turning, a novel and unconventional technique, was used for the turning operation of a newly developed hybrid metal matrix composite of aluminum (A359/B4C/Al2O3) fabricated in-house by electromagnetic stir casting. The objective of the work was to examine the effect of rotational speed on the elements of surface integrity. It involved the measurement of various parameters such as the roughness (Ra, Rq, Rz), morphology of the recast layers, microhardness variation, and the formation of residual stresses on the machined surface and in the subsurface during the operation. The quality of the turned surface was examined by 3D surface visualization images and surface topographical details obtained by an Olympus LEXT OLS 3100 laser confocal microscope. Further, surface study at the microscopic level was done by field-effect scanning electron microscopy (FE-SEM) images to examine the surface defects. The measurement results revealed a successful turning operation, which showed a dull, textured surface without any specific texture or pattern on the machined surface. The surface had many peaks and valleys with small-scale of defects such as surface porosity. However, these defects were negligible and resulted in a smooth surface finish at high rotational speeds.

Keywords

• hybrid mmc
• microhardness
• residual stresses
• surface integrity
• wire electric discharge turning