IJIRST –International Journal for Innovative Research in Science & Technology| Volume 3 | Issue 01 | June 2016 ISSN (online): 2349-6010
Tribological Investigations on Al-Al3Ti In-situ Metal Matrix Composite Veeresha G Assistant Professor Department of Mechanical Engineering New Horizon College of Engineering, Bangalore-560103, Karnataka, India
Abstract In the present study, an attempt has been made to prepare and characterize Al-Al3Ti metal matrix composites with varying percentage of in-situ Al3Ti (3, 5 and 7%). The composites were prepared by the reaction commercial purity aluminum 99.7% and K2TiF6 salt at a reaction temperature of 800 °C. The prepared samples were characterized by optical microscopy. The wear tests were conducted on all the prepared samples by varying parameters like wt. % of Al3Ti particles, normal pressures, sliding speeds. Mechanical properties were assessed using computerized universal testing machine, Brinell hardness tester, Surface roughness tester and micro hardness tester. The worn surfaces were examined by optical microscopy after wear test.Al-3Ti, Al5Ti and Al-7Ti alloys were prepared and effect of Ti content on hardness, tensile strength, volumetric wear rate and surface roughness were examined. Experimental alloys were fabricated by salt route method. Volumetric wear rate of the reinforced Al3Ti, Al-5Ti and Al-7Ti alloys at room temperature were measured. The present results suggest that the wear resistance of AlAl3Ti composites increases with increase in percentage of Al3Ti particles compared to pure aluminum. In addition, the improvement in mechanical properties of the composite was observed in Al-5Ti composite when compared to Al-3Ti and Al-7Ti and to the pure Al. Better tribological properties of these alloys can be achieved at Al-5Ti. Keywords: Al-Al3Ti, Intermetallic compounds, Hardness, Tensile strength, Volumetric wear rate, sliding speed, Surface roughness, frictional force _______________________________________________________________________________________________________ I.
INTRODUCTION
For structural application of moving components, the tribological properties (friction and wear) are considered to be one of the major factors controlling the performance. In recent years, lightweight metal matrix composites (MMC) have received wider attention for their technological application, such as automotive parts etc. This paper reports the tribological behavior of Al based composites reinforced with in situ TixAly and Al2O3 particles. The wear experiments were performed on a newly designed fretting tribometer to evaluate the role of intermetallic particulates on the wear performance of in situ composites against bearing steel under the ambient conditions of temperature (22–25 °C) and humidity (50–55% RH). Based on the topographical observation of the worn surfaces the plausible wear mechanisms are discussed. An important result is that Al-based composites with 20 vol% reinforcement exhibit an extremely low coefficient of friction of 0.2 under unlubricated conditions. Also, around five times lower wear volume is measured with 20 vol% composites when compared to unreinforced Al. During past two decades, requirements for specific property material for advanced aerospace and automobile application have escalated since conventional alloy systems are not suitable there. Attempts to enhance the performance characteristics of monolithic materials by reinforcement with high strength/ high stiffness second phase are therefore required. By selecting the appropriate reinforced constituents of a material that is volume fraction, shape and size. It is possible to design alloys with enhanced strength and stiffness. Polymers, ceramics or metals such as aluminum, magnesium, titanium, copper and nickel alloys serve as matrix materials with whiskers (SiC), monofilaments (SiC, B, W), fiber (SiC, Al 2O3, graphite) and particulate (SiC, Al2O3, Al3Ti) acting as reinforcement. These reinforcements normally strengthen the matrix as they are stronger than the matrix alloys. Due to the presence of hard particles these metal matrix composites (MMCs) are currently being considered as promising tribological materials with applications in the aerospace, aircrafts and in a particular automotive industries. The high strength to weight ratio and wear resistance of aluminum MMCs makes the substitution of steel engine parts such as pistons, liners, clutches, pulleys rockers and pivots by MMCs parts in automobiles. This results in improved engine efficiency a reduction in noise and friction. Aluminum based particulate reinforced metal matrix composites have emerged as an important class of high performance materials for use in aerospace, automobile, chemical and transportation industries because of their improved strength, high elastic modulus and increased wear resistance over conventional base alloys. Recently, in situ techniques have been developed to fabricate aluminum-based metal matrix composites [1-4], which can lead to better adhesion at the interface and hence better mechanical properties. Owing to low density, low melting point, high specific strength and thermal conductivity of aluminum, a wide variety of ceramic particulates such as SiC, B4C, Al2O3, TiC and graphite have been reinforced into it. Among these particulates, Al3Ti has emerged as an outstanding reinforcement. This is due to the fact that Al 3Ti is stiff, hard and more importantly, does not react with aluminum to form any reaction product at the interface between the reinforcement and
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