Microstructure and mechanical properties of autobody steel joined by friction stir spot welding

Abstract

This work investigates the microstructural features and mechanical properties of joints of lowcarbon steel friction stir spot welded by changing tool rotational speed and dwell time. Microstructural evaluation, peeling, tension-shear and micro-hardness tests were employed to characterize the properties of the welded joints. The results show that an increase in the tool rotational speed promotes the formation of more weld flash, and it equally changes the flash morphology from ring flash to a combination of ring and serrated flashes. A fine immediate tool contact region is formed in the stir zone (SZ) and the width of the ITCR increases with the tool rotational speed and tensile-shear failure load. Besides the ITCR, the SZ uniquely consists of the shoulder undersurface region (SZ I) and vortex region (SZ II) with average grain sizes of about 10.9 and 16.66 lm, respectively. An increase in tool rotational speed improves the micro-hardness, and the average diameter of the weld nugget (from 4.5 to 5.5 mm). Base metal-nugget interface failure (650 rpm) and base metal neckinginduced failure (1250 rpm) are the two forms of weld failure obtained in the welded samples.

The effect of hydrogen on the fracture toughness of friction‐stir welded API 5L X70 pipeline steels

“…The failure in the BM (Figure 5) with necking implies that the weld region resists failure under axial loading conditions. These results follow the results reported by other authors 66–68 . Furthermore, the tensile properties of the FSW for both yield strength (YS) and ultimate tensile strength (UTS) exceed the base metal 69–75 .…”

“…These results follow the results reported by other authors. [66][67][68] Furthermore, the tensile properties of the FSW for both yield strength (YS) and ultimate tensile strength (UTS) exceed the base metal. [69][70][71][72][73][74][75] Therefore due to these higher values, the failure occurs in the BM under axial loading.…”

Modeling and optimization of friction stir stitching of AISI 201 stainless steel via Box-Behnken design methodology

“…6a and b. A direct relationship exists between the tool rotational speed and inherent heat input during friction stir-based processing (Ojo, 2019) (Heydari et al 2019). This indicates that the induced heat input (deformation and friction) is significant in improving the load-bearing attribute of the repaired or friction stir stitched joints at a high level of tool rotational speed.…”

Comparison of mechanical performance between friction-stir spot welded and adhesive bonded joints

“…It is the region where the grains are submitted to large plastic deformation and the highest temperature is reached during the welding process, due to the frictional energy coming from the contact of the tool with the joint material. Consequently, the grains recrystallize but do not have time to grow, obtaining a refined and equiaxial T structure [39]. The plastic deformation promoted by the tool in the TMAZ, zone which is also affected by the thermal gradients generated, induces the grain elongation, see Figure 5d.…”