Experiments and Modeling of Fatigue Behavior of Friction Stir Welded Aluminum Lithium Alloy

Abstract

An extensive experimental and computational investigation of the fatigue behavior of friction stir welding (FSW) of aluminum–lithium alloy (AA2099) is presented. In this study, friction stir butt welds were created by joining AA2099 using two different welding parameter sets. After FSW, microstructure characterization was carried out using microhardness testing, scanning electron microscopy, and transmission electron microscopy techniques. In particular, the metastable strengthening precipitates T1 (Al2CuLi) and δ’(Al3Li) seen in the base metal were observed to coarsen and dissolve due to the FSW process. In order to evaluate the static and fatigue behavior of the FSW of the AA2099, monotonic tensile and fully-reversed strain-controlled fatigue testing were performed. Mechanical testing of the FSW specimens found a decrease in the ultimate tensile strength and fatigue life compared to the base metal. While the process parameters had an effect on the monotonic properties, no significant difference was observed in the number of cycles to failure between the FSW parameters explored in this study. Furthermore, post-mortem fractography analysis of the FSW specimens displayed crack deflection, transgranular fracture, and delamination failure features commonly observed in other parent Al–Li alloys. Lastly, a microstructurally-sensitive fatigue model was used to elucidate the influence of the FSW process on fatigue life based on variations in grain size, microhardness, and particle size in the AA2099 FSW.

Research on the Properties and Low Cycle Fatigue of Sc-Modified AA2519-T62 FSW Joint

“…The obtained value of the cyclic strength coefficient (504.37 MPa) is almost three times lower than for the base material (1518.1 MPa) [ 52 ]. Although, the decrease of cyclic strength coefficient is expected for welded joints, in this case, the reported drop is significant and the obtained value is similar to the values reported by research [ 31 , 36 , 55 , 56 , 57 ]. In the next step, the parameters of the stabilized loops were used for establishing the plots of elastic and plastic strain amplitudes vs. number of reversals, presented in Figure 15 .…”

Mechanical and microstructural properties of friction stir welded AA5083 and AA5754 aluminium alloys TOLUN, F.

“…Reducing the feed rates led to increasing heat input to the welding zone. Moderate amounts of heat inputs are suitable for the plastic deformation, stirring, and material flow in FSW [24,37,38].…”

Effect of traverse speed on microstructure and mechanical properties of friction-stir-welded third-generation Al–Li alloy

“…AA2××× alloy when welded using conventional methods generates various defects including oxide layer, distortion, solidification cracking, porosity, etc. [11][12][13][14]. However, voids, tunnel, pinhole, wormhole, kissing bond, lack of penetration and joint-line remnant types of the defects are found in FSW joints due to improper material flow, insufficient consolidation of plasticized material and selection of inadequacy process parameter in FSW [15][16][17][18][19].…”