Mechanical properties of aluminum tailor welded blanks at superplastic temperatures

Abstract

This paper describes an investigation of the mechanical properties of weld material in aluminum tailor welded blanks (TWBs) at superplastic temperatures and discusses the potential application of TWBs in superplastic forming operations. Aluminum TWBs consist of multiple sheet materials of different thicknesses or alloys that are butt-welded together into a single, variable thickness blank. To evaluate the performance of the weld material in TWBs, a series of tensile tests were conducted at superplastic temperatures with specimens that contained weld material in the gage area. The sheet material used in the study was SKY 5083 aluminum alloy, which was joined to produce the TWBs by gas tungsten arc welding using an AA5356 filler wire. The experimental results show that, in the temperature range of 500–550 °C and at strain rates ranging from 10 −4 to 10 −2 s −1, the weld material has a higher flow stress and lower ductility than the monolithic sheet material. The weld material exhibited elongations of 40–60% under these conditions, whereas the monolithic sheet achieved 220–360% elongation. At the same temperatures and strain rates, the weld material exhibited flow stresses 1.3–4 times greater than the flow stress in the monolithic sheet. However, the weld material did show a substantial increase in the strain rate sensitivity when compared to the same material formed at room temperature.