Surface integrity investigation and VIKOR optimisation during the milling of aluminium–lithium alloy using uncoated and PVD-coated carbide tools

Abstract

ABSTRACT In this study, the effect of face milling on the surface integrity of an aluminium–lithium alloy is investigated through an L27 Taguchi design of experiments. Uncoated and PVD-coated carbide inserts are used to investigate the material surface characteristics such as roughness, microhardness, microstructure and residual stresses. Both inserts showed their ability in achieving a better surface finish (Ra ∼ 0.04 µm) than the raw material (Ra ∼ 0.52 µm). Hardness improvement of up to 216.7 HV (uncoated) and 229.3 HV (PVD-coated) from the raw material (180.7 HV) surface is observed. Both inserts showed their ability to generate compressive residual stresses with uncoated inserts producing stresses on the surface. Microstructural changes from milling using both inserts are observed to be minimal. ANOVA showed the effect of process parameters on the surface roughness and microhardness. Furthermore, VIKOR statistical analysis technique is used to identify the optimal conditions for good roughness and microhardness of the alloy.