Analysis of Structure and Shear/Peel Strength of Refill Friction Stir Spot Welded 7075-T6 Aluminium Alloy Joints

Abstract

The article presents an analysis of the macrostructure and mechanical properties of spot welds of joints made by Refill Friction Spot Stir Welding (RFSSW) method. RFSSW is a relatively new technology that is gaining wider use, not only in the automotive and aviation industries because it is a less energy intensive method than resistance spot welding. The primary focus of the article is the effect of welding time on the quality of the welded joints of sheet metal using the aforementioned method. The research was conducted on a joint between two pieces of sheet metal of various thicknesses (1.6 mm and 0.8 mm) made of a common aviation grade aluminium alloy 7075-T6 Alclad. Metallographic sections of select variants were made in order to analyze the structure of the joint. Strength tests with a static load were conducted in different loading configurations. A traditional tensile strength test was conducted on the lap joint, which revealed a complex stress state within the joint and an analogous test was conducted with the use of a stiffening holder that ensured a pure shear state in the joint. Peel tests were also performed on the lap joints with using a special holder.

A Numerical Study on the Effect of Tool Speeds on Temperatures and Material Flow Behaviour in Refill Friction Stir Spot Welding of Thin AA7075-T6 Sheets

“…Additionally, material flow was aided by the material's softening as a result of the increasing temperatures in the SZ with the increase in RS. Increased temperatures allow proper phase change and enhance metallurgical bonding between weldments [33,57]. According to the experimental results, the PR parameter had the least influence on joint strength [31].…”

“…PR/welding time (WT) is the parameter with the least influence on joint strength [18,22,24,31]. In most of the earlier work, it was observed that joint strength is enhanced with an increase in the WT/decrease in PR [8,10,27,32,33]. The increased WT allows a rise in temperature for proper phase change of the material and improves material flowability and mixing.…”

Analytical Approach for Forecasting the Load Capacity of the EN AW-7075-T6 Aluminum Alloy Joints Created Using RFSSW Technology

“…Materials from one batch were used for testing. The selection of the parameter range was carried out on the basis of preliminary tests [19]. On their basis, it was found that the welding time in the range of 1-1.5 s does not significantly affect the LC of the obtained joints.…”

“…In order to more fully analyze the effect of tool depth on weld properties, the plan was extended by one level of the input factor x2 (Figure 3). The selection of the parameter range was carried out on the basis of preliminary tests [19]. On their basis, it was found that the welding time in the range of 1-1.5 s does not significantly affect the LC of the obtained joints.…”