Workability Studies on Al6061 Alloy and Al6061 Metal Matrix Composites Reinforced with Silicon Carbide Particles Under Cold Backward Extrusion: Fid-Bau Portal

Workability Studies on Al6061 Alloy and Al6061 Metal Matrix Composites Reinforced with Silicon Carbide Particles Under Cold Backward Extrusion

Venkatesh, R. / Niranjan, C. A. / Srinivas, S. / Raghavendra, T.

Abstract

In the present work, the effect of cold backward extrusion on non-annealed and annealed Al6061 alloy and Al6061 metal matrix composites (MMCs) reinforced with SiC particles is analysed. The specimens were machined to prescribed size and subjected to cold backward extrusion. Brinell hardness and Ultimate Tensile Strength (UTS) were determined before and after annealing. Microstructure was examined using optical microscope. Scanning electron microscope was used to analyse specimen fracture surface. Al6061-MMCs containing 10% SiC particulates demonstrated better hardness of 62 BHN (without annealing) and 108 BHN (with annealing) compared to base Al6061 alloy. Improved hardness was observed in base alloy as well as composites after cold forging. Microstructure features revealed distribution of large and small grains in Al6061 alloys and comparatively smaller grain distribution in Al6061-MMCs, Zinc stearate lubricant was applied to work piece to minimize the friction between punch and work piece. Fracture of both Al6061 alloy and MMC was observed during backward extrusion due to brittleness of material and induced stresses during casting and machining (without annealing). Some of the common defects such as centre burst and surface cracking were also observed in both as-cast alloy and composites (without annealing). Annealed base alloy and MMC demonstrated good quality of extrusion without surface defects under cold forging conditions. Overall it can be concluded that cold backward extrusion is not advisable for Al6061 alloy and composite without annealing.