Effects of post heat treatment on crack growth behaviour of MIG welded butt joints of dissimilar Aluminum alloys
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Date
2021-02
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Aluminium 7075 and 606I-T6 is one of the widely used materials for various applications in industry, aerospace, utensils, etc. In the present investigation, fatigue crack growth experiments were performed on MIG welded butt joint using filler ER 4043 and Silicon Carbide (SiC) nanomaterial reinforced 7075 filler material. The dissimilar material welded by these filler materials were subjected to three post heat treatment conditions such as artificially aged at 150°C for 16 h (HT1), cyclic solution heat treated at 400°C to 480°C for 2 h (HT2) and combination of both HT3 for 16 h and HT2 for 2 h is (HT3). The precracking was done at Pmax = 2kN and R=0.1. The constant amplitude cracks growth tests were conducted using CT specimen at a maximum load of 5 kN and stress ratio R= 0.1. The test frequency was kept 6 Hz. The results obtained from the crack growth tests were analysed intense of a-N curve, da/dN vs (AK) and Paris growth parameters were determined. The effect of post heat treatment as well as different filler materials on the crack growth were discussed. The fatigue life for MIG welded CT specimen using filler ER 4043 and Silicon Carbide (SiC) reinforced 7075 filler rods at as-weld and three heat treatment conditions HT1, HT2 and HT3 was found to be 27500, 24000, 22500, 21500 and 25500, 23500, 21500,20500 cycles respectively. Scanning electron microscope study of fracture surface at different locations was carried out to investigate modes of fracture due to heat treatments and filler compositions. The results reveal that presence of shiny surface along with tiny holes over the fracture surface leading to partial ductile.