Estimation of deformation behaviour at different weld zones of FSWed 2014 aluminium alloy through impression creep technique

Impression creep (IC) tests of the best-welded specimen at three dissimilar weld zones of friction stir welded (FSWed) 2014 grade aluminium alloy welded with optimized process parameters were carried out at a temperature of 310, 330 and 350 °C and stress regimes of 21, 24 and 27 MPa. The creep deformation properties of the localized zones viz: nugget zone (NZ), thermo-mechanical affected zone (TMAZ) and heat-affected zone (HAZ) of the FSWed material including the base material (BM) were revealed using the power law creep equation and correlated with the variation in microstructural properties. The steady-state creep rate of the individual zones along with the BM was analyzed. The other creep parameters such as stress exponents (n) and apparent activation energy for the IC deformation procedure (Qic) were calculated henceforth. From the calculated n and Qic value, the creep deformation process in the BM as well as in TMAZ and HAZ of the welded material was estimated to be through dislocation glide. Whereas the NZ deforms by grain boundary sliding and this may be due to the heterogeneity in the microstructure. The micro-hardness after IC test was increased for each sample. The outcomes are concluded with the microstructural study of the creep tested sample through optical and field emission scanning electron microscope. The particles agglomeration and dislocation structures at NZ were confirmed by transmission electron microscope (TEM). To observe the composition influence of the precipitated second phase particles on creep behaviour, an energy dispersive x-ray study was also carried out.