Effects of different backing plates and tool design on the flash defect developed during friction stir welding of AA6061 aluminium alloy

Abstract

The growing need for lightweight and higher strength materials, like aluminium alloys, in aircraft, ship construction, and railways has influenced manufacturers to adopt friction stir welding (FSW) due to the excellent mechanical properties of FSW joints as compared to other conventional welding processes. Friction stir welding (FSW) is defined by diverse interactions of thermal, mechanical, and tool geometry effects. The backing plate material is crucial for effective temperature control during the FSW process. Inappropriate FSW process parameters can result in flash defects. Due to extreme heat input, flash may be generated in FSW welds. This investigation aims to determine appropriate process parameters (backing plate thermal diffusivity, welding speed, and tool rotational speed) along with proper tool design to achieve flash defect-free joints. Visual observations indicate that the aluminium backing plate results in flash defect-free joints as compared to other backing plates.