IMPACT OF PLASTIC DEFORMATION ON THE PROPERTIES OF A SELECTED ALUMINIUM ALLOY

This paper reports on an experiment to assess the influence of plastic deformation on the microstructure and properties of EN AW 6012 (AlMgSiPb) aluminium alloy in two states. The first was the initial state with heat treatment T3, and the second was the state after intensive plastic deformation by ECAP (Equal Channel Angular Pressing) technology. The ECAP process was carried out repeatedly at room temperature. In the initial state of the alloy, the process redistributed eutectic Si-particles and increased the strength of the alloy. The mechanical properties and the hardness increased due to intensive plastic deformation (the yield strength increased by 15%, the tensile strength by 6%, and the hardness by 23%). The fracture cracks initiated and propagated mainly along eutectic particles. The fracture area of the ECAPed specimen displayed a typical ductile cavity characteristic.

CHARACTERISTICS OF AA7075-T6 AND AA6061-T6 FRICTION WELDED JOINTS

In this experimental study dissimilar materials of AA6061-T6 and AA7075-T6 having distinctive difference in physical and thermal properties were welded using continuous direct drive friction welding. High strength was achieved by high friction, upset pressure, low burn off length and medium rotational speed. Mechanical characterization and Micro structural behavior of the joint were given the paramount importance in this experimental analysis. The macro structure indicates that change in the direction of flow of grains perpendicular to the initial grain direction of the parent metal. Also the micro structural analysis at the interface zone showed the presence of eutectic particles that are formed as fragmented agglomerates.

The Effect of Magnesium on the Modifying Efficiency of Strontium in A356 Alloy

This study was undertaken to investigate the effect of different concentrations of magnesium (0.2%, 0.3%, and 0.4%) on the modifying efficiency of Sr in aluminium alloy A356. Both sand casting and gravity die castings were taken for the same composition. Modifying efficiency was studied quantitatively by measuring the size and shape of Si eutectic particles by using ImageJ image analyser and giving a Modification Rating (MR), developed by American Foundrymen’s Society (AFS), for each microstructure ranging from 1 to 6, 1 being unmodified and 6 being completely modified very fine structures. Characterisation was done with optical microscope and SEM equipped with EDS and XRD. Mechanical testing involved hardness test in both as cast and standard T6 condition.

Experimental Investigation of Mechanical and Chemical Properties of Aluminium Reinforced with MWCNT

Carbon Nanotubes (CNT’s) have recently been found to possess extraordinary mechanical, thermal and electrical properties. Extensive studies on the properties of CNT’s as a re-inforcing agent in Metal Matrix Composites are being investigated. In this study, powder metallurgy technique has been employed for the matrix material being Aluminium 6063 with CNT in varying concentrations as reinforcing agent. The powders are mixed thoroughly using ball milling and are compacted in a compacting die made of D-2 Steel to make green compact. It is then sintered at 350°C to 550°C at a rate of increase of 50°C per hour. Chemical, Microscopic examination, Compression and Hardness tests were performed on the specimens and were compared with pure aluminium specimens to show the effects of varying concentrations of CNT. The study indicated that there was no improvement in hardness of the composite on addition of CNT while there was an increase in compressive strength. The microstructure of pure aluminium and Al-CNT composite had fine grains of pure aluminium particles and Al-Si eutectic particles throughout the matrix phase.