TESTING 1-2-3
Investigating the Machinability of Aluminum-Silicon Cast Alloys
A series of drilling tests highlights how microstructural differences can affect machinability and tool wear. A MODERN CASTING STAFF REPORT
microstructural properties to better understand their effects on machin- ability. Tese alloys can have radically different machining characteristics as a result of microstructural differences, which in turn generate variations in composition and/or in manufacture. A team of researchers investigated
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the impact of microstructure and tool material on the machinabil- ity of aluminum-silicon alloys. Te results appear in the paper, “Effects
ADDING IT ALL UP Breaking down the latest research is as easy as 1-2-3.
“Effects of Alloying Elements and Cutting Tool Materials on the Machin- ability of Aluminum-Silicon Cast Alloys” Guillermo Garza-Elizondo, Ehab Samuel, Agnes Samuel and Fawzy-Hosny Samuel, Université du Québec à Chicoutimi, Chicoutimi, Québec, Canada; Adel M.A. Mohamed, Qatar Univer- sity, Doha, Qatar; Saleh Alkahtani, Salman Bin Abdulaziz University, Al Kharj, Saudi Arabia
Background—The machining characteristics of aluminum-silicon alloys can vary radically because of microstructural differences, which in turn generate variations in composition and/or in manufacture. The research team examined differences in machinability and drilling force and the impact of tool material on tool wear and life. Procedure—Test blocks of two 396 alloy variants and a B319.2 alloy were machined with four different drills. The four tools were used on the three alloys in fatigue testing, with the goal number of holes being 2,016. Results and Conclusions—The 396 alloys’ higher silicon content (10.8%) compared to the B319.2 alloy (7.5%) required greater cutting force and torque but did not affect tool life. The high precision solid carbide drill was best for the 396 alloys, requiring the lowest drilling force and torque, while the cobalt drill was best for the B319.2 alloy.
he increased use of aluminum-silicon alloys, particularly in the auto- motive and aerospace industries, has led to additional research into
of Alloying Elements and Cutting Tool Materials on the Machinability of Al-Si Cast Alloys,” by Guillermo Garza-Elizondo, Ehab Samuel, Agnes Samuel and Fawzy-Hosny Samuel, Université du Québec à Chicoutimi, Chicoutimi, Québec, Canada; Adel M.A. Mohamed, Qatar University, Doha, Qatar; and Saleh Alkahtani, Salman Bin Abdulaziz University, Al Kharj, Saudi Arabia. Drilling is one of the most common
machining processes in the automotive and aerospace industries. In response to market pressures, drilling cycle times must be decreased with met- alcasters still meeting tight tolerances. Aluminum-silicon alloys, which have
a relatively high abrasive action, are machined primarily using solid carbide drills. Te research team designed a series of tests using four different drills on three alloys to examine the effects of ferrous intermetallics and free-cutting elements on the machinability, drilling force and torque, and how tool material affected tool wear and life.
Question What effects do microstructural
changes in aluminum-silicon alloys and drilling tool material have on overall machinability?
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Background In an alloy, the percent-
age of silicon and the shape and distribution of the particles play an important
role in determining machinability. An aluminum matrix containing eutectic silicon comprises the microstructure of an aluminum-silicon alloy. Tis silicon can appear as needle-like crystals and plates or a refined fibrous structure, depending on the level of chemical modification and the casting’s cooling rate. Te machining characteristics of aluminum-silicon alloys depend on microstructural features such as shape, size and morphology of the eutectic silicon particles, the dendrite morphology of α-aluminum, and the morphology and amount of other intermetallics. Measuring thrust force (i.e., the
force component in the cutting direc- tion) and torque (i.e., the moment of force about the tool’s axis of rotation) is a common technique for moni- toring tool wear. Previously, using a microcomputer-based feedback
January 2014 MODERN CASTING | 47
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