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Warm Forming of Fully-Strengthened Aluminum Alloys for High Strength Automotive Applications

IP.com Disclosure Number: IPCOM000201791D
Publication Date: 2010-Nov-23
Document File: 1 page(s) / 138K

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Warm Forming of Fully-Strengthened Aluminum Alloys for High Strength Automotive Applications

Traditional Approach

The current trend in achieving high strength aluminum panels in the automotive industry is the use of heat-treatable alloys such as the AA6xxx series. These alloys are typically received by the stamping facility in the T4 condition (naturally aged). After forming, the panels are exposed to elevated temperatures during the paint bake cycle which results in an increase in strength (yield and ultimate stress).  This strategy of strengthening the alloy post-forming allows for the panel to be stamped in the softer state thus helping formability and reducing quality issues such as springback.  The required gauge of strength-limited panels is dictated by the final, in-service yield stress of the panel after painting. While this approach has several benefits, the paint bake cycle is insufficient to fully strengthen these alloys.  Additionally, there appears to be a trend in automotive painting technology to move to lower temperatures and shorter times.  This would result in lower final yield stresses and hence the need to use thicker gauge material.

New Approach

One method of capitalizing on the ability of these alloys to gain more strength than what is possible with the current paint bake processes is to fully strengthen (or harden) the alloy prior to forming.  Strengthening of heat treatable alloys can be accomplished with a combination of work hardening and artificial aging (i.e. heat treatment).  The former can be accomplished either during the rolling process where strain is imparted on...