INFLUENCE OF NANOFILLERS ON MECHANICAL AND MICROSTRUCTURAL ANALYSIS OF FRICTION STIR WELDED DISSIMILAR ALUMINIUM ALLOYS

Abstract

n this investigation, friction stir welding has been conducted on dissimilar aluminium alloys Al 2024- T351 and Al 6061- 1651 by keeping alloy Al 6061- T651 on the retreating side. Two different type of fillers namely silicon carbide (SiC) and alumina (A1203) were incorporated at the mating line of two plates with three different volume fractions of 0.72, 1.44 and 3.53 prior to welding. Rotational speed and traverse speed used during this study was 635 rpm and 19 mm/min respectively. Furthermore, microstructure, mechanical properties, fracture surface analysis, XRD analysis and thermal analysis of all the samples were carried out. Then an approach has been made to study the effects of adding these fillers on the microstructural, mechanical as well as thermal behavior of the dissimilar butt joint. Micrographs obtained from all the specimens with different volume percentage of particles showed a uniform distributions of particles at the weld center though there were few particles seen to be agglomerated along the interface of weld and base materials towards the retreating side. Electron back scattered diffraction (EBSD) analysis showed a relatively lower percentage of recrystallization after the addition of SiC particles at the centerline. Average Vickers hardneess of nugget zone was - increased upto 117.78 HV and 120.85 HV after addition of 3.53 vol.% of SiC and Al2O3 respectively. While the simple dissimilar weld has a average Vickers hardness of 103.71 HV. Transverse tensile specimes showed no distinct differences in strength though little more elongation was achived as compared to simple FSW joint, on those samples where particles were incoporated and two passes of FSW was carried out. Longitudinal tensile testing of samples showed a improved UTS value after the addition of 1.44 vol.% of SiC and Al2O3. UTS value increased upto 416.02 MPa for 1.44 vol.% addition of SiC, while the simple one with no particles failed at a lower UTS of 353.5 MPa.