چكيده به لاتين
Today, with enhance in the need of using materials with new properties such as strength, weight, hardness and so forth, position and value of metal matrix composites have become cleared. Using ceramics and hard particles as composite reinforcements categorized these materials as difficult-to-cut. Then, obtaining a proper machining condition is very remarkable. In this thesis, machinability of AZ91 composites reinforced by SiC particles, as one of lightest metal matrix composites, are considered. To this end, machining of composites with two volume fractions of 2.5 and 5% are evaluated. Due to the abrasiveness nature of the work-pieces, the hardest coated cemented carbide with grade TH1000 is used to machine the composite materials. To assess the tool wear, effects of the most important machining parameters such as cutting speed and feed rate are studied. Additionally, am empirical-experimental model is developed to predict the flank wear. Moreover, effects of cutting speed, feed rate and depth of cut on the surface quality, machining force and chip morphology are evaluated. Regarding the results, feed rate is the most significant parameter in the carbide tool wear when machining of AZ91/SiC composites. The developed model predicts tool wear accurately. Due to the abrasiveness of SiC particles, the tools are won out in a short time and detached tungsten carbide from the tool surface could reduce the finished surface. The pits, broken SiC reinforcements, tungsten carbide pieces adhered to the work piece surface, micro cracks, pulled out particles are the main defects decreasing the surface quality. With increase in the composites volume fraction, the surface defects increases in return. Also, chips in machining of Mg-based composites tend to become semi continues and serrated and their tendency to gets smaller size increases with increase in the volume fraction.
