Abstract
This study was undertaken to emphasize the influence of Sn and Bi addition on the machinability of Sr-modified, grain-refined, and heat-treated Al–Si B319 and 396 alloys. Drilling and tapping tests were conducted to examine the cutting forces, tool life, tool wear, built-up edge evolution, and chip shape. Microstructures were examined using optical and electron microscopy. Drilling test results show that the B319.2 alloy with 0.15%Sn yields the longest drill life, i.e., twice that of the B319.2 alloy containing 0.5%Bi, and one-and-a-half times that of the B319.2 alloy containing 0.15%Sn + 0.5%Bi. The presence of 0.5%Bi in the B319.2 alloy causes a deterioration of drill life (cf., 1101 holes with 2100 holes drilled in the B319.2 alloy containing 0.15%Sn). The α-Fe phase in the 396 alloy produces the highest number of holes drilled compared with alloys containing sludge or β-Fe. The presence of sludge decreases the drill life by 50%. Built-up edge (BUE) measurements and optical photographs show little change in the BUE width for different numbers of holes except for the B319.2 alloy containing 0.5%Bi, which shows a slightly lower width (0.166 mm) compared with that containing 0.15% Sn (0.184 mm) or 0.15%Sn + 0.5%Bi (0.170 mm).
Highlights
Considering machinability as a system property allows us to define machinability as an interaction phenomenon between the workpiece, cutting tool, and cutting medium for different removal sequences such as turning, drilling, tapping, milling, and sawing under different cutting conditions, e.g., cutting speed, feed rate, and depth of cut [1–5]
The current study addresses this point by investigating the influence of individual and combined additions of Sn and Bi on the machinability of Sr-modified, grain-refined, and heat-treated Al-(7–11)%Si alloys, where the machinability criteria relate to tool life, tool wear, evolution of the built-up edge (BUE), cutting forces, and moment analysis
The following conclusions may be formulated from experiments conducted to study the influence of Sn and Bi additions on the machinability characteristics of Sr-modified, grain-refined, and heat-treated 396 and B319.2 alloys
Summary
Considering machinability as a system property allows us to define machinability as an interaction phenomenon between the workpiece (with different alloying elements such as Fe, Cu, Mg, and Mn), cutting tool (tool material and geometry), and cutting medium (wet or dry cutting) for different removal sequences such as turning, drilling, tapping, milling, and sawing under different cutting conditions, e.g., cutting speed, feed rate, and depth of cut [1–5]. Free-cutting constituents are formed in the presence of alloying elements with the following properties: (a) insolubility in both liquid and solid Al; (b) a low melting point with regard to Al; (c) not forming intermetallic compounds with Al or other alloying elements; and (d) having lower hardness values compared with the Al matrix. These conditions may be fulfilled by using lead (Pb), bismuth (Bi), tin (Sn), cadmium (Cd), indium (In), antimony (Sb), or a number of other elements that are, unusable from the practical point of view. The current study addresses this point by investigating the influence of individual and combined additions of Sn and Bi on the machinability of Sr-modified, grain-refined, and heat-treated Al-(7–11)%Si alloys, where the machinability criteria relate to tool life, tool wear, evolution of the BUE, cutting forces, and moment analysis
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