Influences of Iron Content and Solidification Rate on Mechanical Properties of 6022 Base Aluminium Alloys

Abstract

The influences of iron content (0.2-1.0wt%) and solidification rate (3-1200K/s) on mechanical properties of 6022 base aluminum alloys were investigated. Molten alloys were cast into about 3 mm thick plate by a vertical-type high speed twin roll caster (HSTRC). Conventional book-type mold casting with thickness of 5 mm and 50 mm were also fabricated for the purpose of comparison. The castings were rolled into 1mm-thick sheets and then heat-treated. Iron content had a small effect on tensile strength of the sheet for both T4 temper and after baking-treated conditions. Meanwhile, elongation decreased with increasing iron content. Silicon content was considered to be sufficient to maintain age-hardenability of 6022 alloy with a high iron content. Solidification rate also had a small effect on the strength, with HSTRC sheet exhibiting a slightly higher strength. This is considered to be due to higher solute content in the Al matrix of the rapidly solidified HSTRC product. Bendability was also deteriorated with the increase of iron content. The deterioration was remarkable for the sheet produced from the 50 mm-thick plate with the low solidification rate. Improved bendability of the sheets fabricated from high solidification rate products was considered to be mainly due to the finer second phase particles.