Effect of operating parameters on the drilling behavior of Zr 57.5 Cu 11.2 Ni 13.8 Al 17.5 bulk metallic glass
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Ghulam Muhammad Department of Mechanical Engineering, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad, Pakistan
Hasan Bin Awais Department of Metallurgy and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad, Pakistan (Received 22 July 2013; accepted 17 October 2013)
Zr-based bulk metallic glasses (BMGs) exhibit superior physical and chemical properties in comparison to their crystalline counterparts. In the present work, drilling behavior of Zr57.5Cu11.2Ni13.8Al17.5 BMG was investigated at various operating conditions. Drilling was performed using high-speed steel (HSS) and carbide bits. Chip morphology, chip light emission, and burr formation at various drilling parameters were studied to achieve a feasible operating condition for drilling hole without light emission, chip clogging, and debris accumulation. Short spiral chip morphology which is considered ideal in the drilling process was observed at relatively low feed rate (1.5 mm/min) and medium spindle speed (1500 rpm). This also resulted in a small amount of molten debris around the entry hole. It was observed that at the same feed rate, the gradual increase in the speed of the HSS drill bit results in more light emission from the machining surface, whereas no light emission was observed in the case of the carbide drill bit at all drilling parameters.
I. INTRODUCTION
Bulk metallic glasses (BMGs), during the past few decades have emerged with eye catching properties. BMG has no long-range atomic order.1,2 Lacking in longrange atomic arrangement, they are free from defects present in the crystalline structure. They possess high strength and high elastic strain, but their structural applications are limited because of their low plasticity.3 In comparison to other crystalline alloys of identical composition, these materials excel in mechanical, magnetic, and corrosion properties.4–6 Machining is one of the important manufacturing techniques used to generate parts with complicated shapes and high dimensional accuracy. To enhance the applications of BMGs, establishment of suitable machining techniques with effectiveness and precision is imperative. Since BMG is a relatively new class of materials, most of the research was dedicated to the investigation of its structural and thermal characteristics. So, the deformation behavior and the mechanism of chip formation in BMG cutting processes are poorly understood, to date. So far, limited work has been
carried out on the machining (cutting, drilling, grinding, etc.) of BMGs.7–10 Among various machining techniques, drilling is an important process for hole making. Drilling is relatively more complicated than the turning process in reference to tool geometry and work piece deformation. Deformation characteristics of the drilling process for BMG are not well understood yet. To our knowledge, very limited literature is available on the drilling behavior of BMGs.9,10 In this study, an attempt has been made to understand the drilling behavior of a Z
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