Heat treatment and its effect on machining induced surface roughness of cast and additive manufactured AlSi10Mg

The study investigates the post-printing machinability of AlSi10Mg aluminum alloy, with a primary focus on evaluating T6 heat treatment influence on the cutting force and surface quality of additive manufactured material while comparing the outcomes with the cast alloy. Milling experiments were performed on untreated and heat-treated specimens using a range of cutting speeds and feed rates. Results revealed that the surface roughness of as-cast AlSi10Mg alloy was 50.5-532.3% higher than that of the as-printed material. This was attributed to the coarser microstructure and lower microhardness (73.04 HV) of the as-cast alloy, which led to increased plastic deformation during machining, leading to increased surface roughness, especially at lower feed rates. In contrast, the fine cellular microstructure of the as-printed alloy enhanced the microhardness (140.3 HV) and deformation resistance, producing better surface quality. T6 heat treatment significantly affected the surface roughness of the cast and AM aluminum alloy. While heat treatment enhanced the surface finish of cast alloy, it reduced the surface roughness in the printed alloy. T6 heat treatment refined the microstructure of cast and printed alloys, increasing microhardness (126.1 HV) and reducing plastic deformation in cast alloy while reducing the microhardness (78.7 HV) and increasing the ductility of the printed alloy, potentially increasing the surface roughness. Despite the treatment, surface roughness of heat-treated cast alloy remained 19.3-38.2% higher than that of the heat-treated printed material. Cutting force analysis showed that additively manufactured (AM) specimens experienced a 49.5-178.1% increase in cutting force compared to as-cast specimens. However, when heat-treated, the AM specimens exhibited a 16.9-67.1% reduction in cutting force relative to untreated AM parts. In contrast, heat-treated as-cast specimens showed a moderate increase in cutting force, ranging from 17.1 to 56.3%, compared to their untreated counterparts. The findings emphasize the significant influence of material manufacturing route and heat treatment on the machining outcomes. The results show that the section on milling process variables depends on the material fabrication route and heat treatment applied during the post-processing stage.