Influence of Grain Refinement, Modification and Turning Inserts on Machinability and Surface Characteristics of Hypoeutectic Al-Si Cast Alloys

摘要

The microstructures, cutting force and surface characteristics of hypoeutectic Al-Si cast alloys were studied after various melt treatments like grain refinement and modification. Results indicate that combined grain refined and modified Al-7Si-2.5Cu cast alloys have microstructures consisting of uniformly distributed α-Al grains, eutectic Al-silicon and fine CuAl{sub}2 particles in the interdendritic region. These alloys exhibited better machinability and surface characteristics in the cast condition compared with the same alloy subjected to only grain refinement or modification. Performances of the turning inserts (Un-coated, PVD and Polished CVD diamond-coated) were evaluated in machining hypoeutectic Al-Si cast alloys under dry environment using a lathe. The Polished CVD diamond-coated insert outperformed the Un-coated or PVD-coated cutting inserts which suffered from sizeable edge buildup leading to higher cutting force and poor surface finish. The Polished CVD diamond-coated insert shows a very small steady wear without flaking of the diamond film during cutting. This paper attempts to investigate the influence of melt treatments on the microstrutural changes in the hypoeutectic Al-Si cast alloys and their cutting force and surface finish when different turning inserts used.