EBSD Results of Material Flow and Microstructural Changes Around Tool Pin for the Dissimilar Friction Stir Welded AA6082
- PDF / 5,022,502 Bytes
- 10 Pages / 595.276 x 790.866 pts Page_size
- 100 Downloads / 205 Views
REVIEW
EBSD Results of Material Flow and Microstructural Changes Around Tool Pin for the Dissimilar Friction Stir Welded AA6082T6 and AA7075-T651 K. T. Thilagham1 • S. Muthukumaran1
Received: 26 February 2020 / Accepted: 7 August 2020 Ó The Indian Institute of Metals - IIM 2020
Abstract Frictional stir welding (FSW) generally experiences the forces Mode I axial metal flow and Mode II shear deformation around the rotating pin, along the welding direction to produce high-efficiency joints. The dissimilar FSW of AA6082/7075 joint was fabricated utilizing the process parameters such as rotational speed (R) of 900 rpm, travel speed (S) 90 mm/min, tilt angle (T) 2° and plunge depth (t) 0.9 mm. Subsequently, the zone-wise EBSD and metal flow analyses were carried out and compared with the results of the microstructure and the microhardness. Distinct variations of Mode I and Mode II metal flow and fine grain formation in weld nugget have been shown here. Keywords EBSD maps Flow arm Tool pin Microstructure Microhardness
1 Introduction Compared to structural-based AA6082 alloy, the aerospace-based AA7075 alloy is high in strength. These alloys can be dissimilarly joined using pulsed gas tungsten arc welding (GTAW) with ER5356 filler material, high-energy (laser/electron) beam welding and/or hybridization processes, which are associated with various solidification defects [1–3]. However, the defectless, high-strength joint can be established by means of friction stir welding. Most FSW researchers reported the high weld nugget (WN) & K. T. Thilagham [email protected] 1
National Institute of Technology, Tiruchirappalli, Tamilnadu 620 015, India
strength and the lower heat affected zone (HAZ) hardness [4–8]. Hence, it is significant to know how the material moves in weld nugget. Some of the metal flow research results are highlighted here. Ying Li et al. [9] clarify the microstructural variations of superplastic flow, grain formation and dislocations in the workpiece. While welding the material, it extrudes around the retracting side (RS) and rises in the weld as it moves around the pin. First, the metal flows from the front of the advancing side (AS) to the retracting side. Second, the material from the retracting side fills onto the advancing side. The mechanical properties of the welding therefore depend on the shearing surfaces of these two processes [10, 11]. Muthukumaran et al. investigated the two modes of flow as the axial force as well as the shear force around the pin on the FSW 6061. This has been illustrated in this research here [12]. Figure 1a shows the material movement in the weld nugget as (i) Mode I material movement by axial force through shoulder on the upper surface of the weld and (ii) Mode II material shearing in the stir zone, generating excessive frictional heat by rotation of the pin in the welding direction. The grain size, shape and orientation relationships that control the properties and performance of the crystalline material can be microstructurally characterized and analyzed using
Data Loading...
