Fabrication and Study of the Mechanical Properties of AA2024 Alloy Reinforced with B4C Nano-particles using Ultrasonic cavitation method

Govind Nandipati
2013 IOSR Journal of Mechanical and Civil Engineering  
Metal matrix nanocomposites (MMNCs) with the addition of nano-sized ceramic particles can be of significance for automobile, aerospace and numerous other applications. The physical and mechanical characteristics of the light refractory carbides such as SiC, TiC and B 4 C make them suitable for being used as reinforcement in aluminium base metal matrix composites This paper presents a technique for an inexpensive fabrication of bulk lightweight MMNCs with reproducible microstructures and
more » ... properties by use of ultrasonic nonlinear effects, namely transient cavitation and acoustic streaming; to achieve uniform dispersion of nano-sized B 4 C particles in molten aluminum alloy. Nano-sized B 4 C p enhanced properties of aluminium matrix composites, with 1.5%wt of B 4 C. As compared to the base metal alloy, the mechanical properties including tensile strength and yield strength of the nanocomposites were improved significantly, while the ductility of base metal alloy matrix castings was retained. Micro structural study was carried out with an optical microscope and SEM which validates a good dispersion of nano-sized B 4 C p in metal matrix. Mechanical properties of the as-cast MMNCs have been improved significantly even with a low weight fraction of nanosized B 4 C. Fabrication and Study of the Mechanical Properties of AA2024 Alloy Reinforced with NanoB 4 C p www.iosrjournals.org 2 | Page magnesium. Due to the addition of nano SiC p , the grain size of magnesium was refined. SiC nanoparticles bonded well with Mg matrix without forming an intermediate phase. The mechanical properties of the Mg/SiC nanocomposites, the yield and tensile strengths, were improved significantly, while the ductility of pure magnesium was retained [4]. The yield strength and ultimate tensile strength of Mg/ 2%SiC, Mg-4Zn/1.5%SiC and Mg-(2, 4)Al-1Si/2%SiC nanocomposites were improved significantly as compared to those of unreinforced pure magnesium, Mg-4Zn and Mg-(2, 4)Al-1Si matrices. The good ductility of the matrices was twice that of pure Mg-4Zn [5]. Yong Yang, Xiaochun Li[6] have fabricated Bulk Al-based nanocomposites that enhanced the mechanical properties with nanosized SiC p by an ultrasonic based nanomanufacturing process. The microstructural study reveals that high-power ultrasonic cavitation is an effective method to disperse nano SiC p particles in aluminum A356 alloy which enhances the wettability between the particles and Al matrix.. Magnesium alloys--one third lighter than an equal volume of aluminum alloys--are one of the lightest metallic structural materials and are very attractive for applications in automotive and aerospace systems. The need for complex structural components of high performance magnesium materials is expected to continuously increase as automotive and aerospace industries are forced to improve the energy efficiency of their products. Nanoparticle reinforcements can increase the matrix mechanical strength by more effectively promoting particle hardening mechanisms than micron size particles. A fine and uniform dispersion of nanoparticles provides a good balance between the strengthener (non deforming particles) and inter-particle spacing effects to maximize the yield strength and creep resistance (by mechanisms such as dislocation bowing around the particles and pinning down dislocations at the particles by rapid diffusional stress relaxation at elevated temperatures) while retaining the good matrix ductility [7]. S. M.Zebarjad et al. [8] concentrated their study on the role of particle size of silicon carbide (SiC) on dimensional stability of aluminium. Al/SiC composites were reinforced with different sizes of SiC particles (25μm, 50μm, and 70 nm).The results showed that for all materials, there was an increase in length as temperature increased and the temperature sensitivity of aluminum decreased in the presence of both micro-and nanosized silicon carbide and dimensional stability of Al/SiC nanocomposite was better than the conventional Al/SiC composites. Different volume fractions of nano-alumina(Al 2 O 3 )particles were dispersed into the A356 aluminum alloy by a mechanical stirrer to avoid agglomeration and for segregation of particles. The microstructural characterization of the composite samples showed uniform distribution of reinforcement, grain refinement of aluminium matrix and presence of the minimal porosity. Due to the presence of nano-Al 2 O 3 , significant improvement in hardness, 0.2% yield strength, UTS and ductility were observed [9].Due to the unique tailorability, aluminium composite materials have wide applications in aerospace and automotive industries. Earlier, fine particles of SiC p are to be reinforced in aluminium 6061 alloy which improve mechanical properties slightly. Due to the presence of cavities and agglomerates there is less significant improvement in the properties [10]. In recent years, Lan et al. and Yang and Li [11,12] developed a new nanomanufacturing method that combines solidification processes with ultrasonic cavitation based dispersion of nanoparticles in metal melts. Ultrasonic waves can produce transient cavitations of the order of nanoseconds, "micro-hot-spots" that can have temperatures of about 5000°C, pressures above 1000 atm. that distribute and disperse nano particles uniformly. C.F.Deng et. al [13], reinforced Carbon nano tubes(CNT) in the aluminum alloy matrix with iso-static pressing followed by hot extrusion techniques. The mechanical properties are affected by carbon nano tubes content. At 1.0%wt of CNTs the mechanical properties increased and decrease at higher %weight. The more percentage of Si constrains the reaction between the SiC and Al in the matrix. It is observed that viscosity of the molten metal increased due to the addition of the nano SiC particles [14]. In this paper, B 4 C/AA2024 composites are fabricated by casting using high-intensity ultrasonic wave technique. The microstructure and microhardness of these composites are investigated. 157 160 155 Hv-after rolling 142 145 149 153 156 158 162 157 TENSILE TESTS: The tensile specimens are prepared with gauge length 28mm and cross sectional area as 5x6mm 2 .The tests are conducted on 2Ton extensometer. The ultimate tensile strength and yield strength of the base metal Fabrication and Study of the Mechanical Properties of AA2024 Alloy Reinforced with NanoB 4 C p www.iosrjournals.org 4 | Page AA2024 are found to be 420MPa and 276MPa respectively. Also the tensile tests are conducted on metal matrix nano composites and after rolling and the results presented in tables below. With only 1.5% by weight of nano B 4 C particles the ultimate tensile strength has been increased by 6% and reads 442MPa.The higher dislocation density in the MMNC is responsible for strengthening mechanism. This dislocation phenomenon is due to the difference in thermal expansion coefficients between matrix and uniformly dispersed nano B 4 C particulate, which act as barriers for dislocation movements. The coefficient of thermal expansion mismatch the strain between the aluminum alloy metal matrix and the reinforcing nano B 4 C particulate. The plastic deformation of the ductile aluminum alloy metal matrix in the presence of discontinuous B 4 C reinforcements, is non uniform. This is due to the hard, brittle and refractory particles resisting the plastic flow of the soft, ductile and plastically deforming aluminium alloy metal matrix. The Ultimate tensile strength and Yield strength of the MMNC is increased for various wt% of nano particlesupto1.5wt% and decreased at 2wt%.This decrease is due to the formation of agglomerates and voids in the matrix. Abstract: The Aluminium Industries Ltd was one of the leading switchgear manufacturers in India. It flourished in late 1960's. The company then faced severe financial stringency and doomed in 1985. This paper is based on an industrial training carried out at the company. The performance analysis and problem identification were carried out as part of the study and is summarised through this paper. The real problems at the company could be identified and suitable corrective measures could solve the problem and upheld the company in future.
doi:10.9790/1684-0740107 fatcat:fur4jegzvngx5j7jbzowan4d6a