3.2.1. AA5754 structural automotive sheet
Due to its good forming ability, AA5754 aluminium sheet normally
is supplied as structural inner panel. In this study, AA5754
in 2.0mm gauge was used throughout the project. As mentioned
earlier, the cleaning process determines the level of oxide
film/disrupted layer remaining at the sheet surface. In order to
examine the effect of disrupted surface layer on RSW process, two
batches of AA5754 were studied. One batch had full electrolytic
cleaning, pretreatment PT2 and solid wax lubricant ALO70; whilst
the other had been given a reduced cleaning process, but received
the same specification of pretreatment and lubricant. Both batches
of AA5754 fulfil the present requirements for self-piercing riveting
(SPR) and adhesive bonding. Tests were also carried out on the
AA5754 sheet with the wax lubricant removed to assess the combined
effect between pretreatment and wax on the feasibility and
quality of the process. The composition and mechanical properties
of the AA5754 are shown in Table 1; whilst Table 2 lists the surface
conditions tested for the AA5754 sheet.