Abstract
Aluminum alloys offer high specific strength than advanced high strength steels, making them preferred candidates for automotive light weighting. Among them, AA7075 aluminum alloy offers significantly higher strength than 5xxx and 6xxx alloys and is considered an attractive candidate by automotive OEMs for structural applications such as door intrusion beams, B pillars etc. There are several challenges in implementing AA7075, such as long artificial aging time to reach peak strength, joining method and corrosion resistance. In this study, an artificial aging practice that significantly reduces aging time was explored and its influence on mechanical properties of AA7075 was investigated in comparison with conventional peak age practice. In addition, this practice offers a potential solution for joining through self-piercing riveting. Moreover, the effect of artificial aging on corrosion, specifically intergranular corrosion (IGC) and stress corrosion cracking (SCC) was evaluated. The results are discussed with in depth analysis and correlation with microstructure.
Highlights
Today, automotive OEMs are constantly pursuing ways to improve vehicle fuel economy to bring more value to customers and reduce carbon footprint to combat global warming and meet more stringent government regulations
The focus of this paper is to provide a comprehensive solution to implement Novelis AdvanzTM s701 (AA7075) alloy for complex automotive components through hot stamping process
Starting with an as cold rolled F temper, the material was solutionised at 480qC for 5 minutes followed by quenching in temperature controlled water bath to simulate quench rate > 350qC/sec similar during hot stamping process [13]
Summary
Automotive OEMs are constantly pursuing ways to improve vehicle fuel economy to bring more value to customers and reduce carbon footprint to combat global warming and meet more stringent government regulations. In order to fully utilize its high strength, 7xxx alloys need to be artificially aged to peak aged condition (T6 temper). The difference being 7xxx series aluminum starts in F temper, is solutionized in a furnace, subsequencially formed and quenched rapidly in a water cooled stamping die. It requires a post forming artifical aging cycle to achieve high strength. In order to achieve full hardened T6 temper, AA7075 alloy requires long artificial aging time (i.e. 24 hours). Such a long practicemakes implemention of AA7075 difficult and can result in higher cost especially for high volume production. Corrosion performance of the alloy, IGC and SCC in the proposed temper was investigated
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