Influence of Aluminum Casting Alloy Metallurgical Factors on Machinability

Machinability of Al-(7-11%)Si casting alloys :

“…Jorstad, 3 ' 4 reported that heavy elements, such as iron, manganese, and nickel have a negligible effect on microhardness and on the tool-edge build-up in 380 die casting alloys.…”

“…These phases are dominant in slowly-cooled castings, whereas the metastable phases AlgFe (orthorhombic) and cc-Al2oFe5Si2 (cubic) only occur in rapidly quenched material. 35 ' 39 The a phase is reported as having a hexagonal structure with the parameters a=12.3 Â, c=26.3 Â, a density of 3.58 g/cm 3 , and it appears in the form Chinese-script particles. The a-AlFeSi phase presents certain characteristics and may be described as showing irregular curved crystal growth conforming to the complicated shape of the interdendritic spaces during solidification.…”

“…9 Chips, with their length and curl, as well as the ease or difficulty associated with their removal and handling influence the surface finish. 3 The importance of the type of chip depends on several variables such as the drilling speed, the feed rate, and the mechanical and thermo-physical properties of the workpiece itself.…”

“…7 The most common types of machining are traditional machining such as turning, milling, and drilling, as well as nontraditional machining such as chemical machining, electrical discharge machining (EDM), and electrochemical machining (ECM). With regard to the machinability of aluminum alloys and castings, it is necessary to take into account several factors which govern the condition of the work material and are determined by: 3 • alloy chemistry, microstructure, and properties;…”

“…The a-Fe phase is reported as having a hexagonal structure with the parameters a=12.3 Â, c=26.3 Â, and a density of 3.58 g/cm 3 . The platelet-like /?-Fe phase was not in evidence because of the higher Mn/Fe ratio in the G2 alloy of -1.04; this ratio promotes the formation of the a-Fe phase at the expense of the /?-Fe phase.…”