How do I increase uniform elongation without losing yield strength in 5754-O?
How do I increase uniform elongation without losing yield strength in 5754-O?
(OP)
I'm trying to get 1.5 mm AA5754-O sheet to 19% minimum uniform elongation (consistently) while maintaining 105 MPa yield minimum. I can easily get one without the other, of course. I can get both, on occasion, but it's not consistent from sample to sample. At the very best, the yield strength is always borderline on the low side and the uniform elongation is borderline as well. Discontinuous yielding complicates the matter by adding to the variability of the uniform elongation results. I'd like to be "safely" within the specification. I've tried chemistry changes and rolling practice changes, and I've experimented with final anneal temperatures (within the limits of a batch furnace), but so far nothing has worked. I'm sure there are many things to consider, and I know I'm probably not giving enough info for specific answers at this stage, but I need to get some guidance and suggestions on which direction to take. Unfortunately, I don't have an R&D department or an extensive list of in-house technical resources on-hand, so I'm hoping there are some knowledgeable folks out there who can help! I'm certain someone out there is very familiar with this issue.





RE: How do I increase uniform elongation without losing yield strength in 5754-O?
RE: How do I increase uniform elongation without losing yield strength in 5754-O?
RE: How do I increase uniform elongation without losing yield strength in 5754-O?
Maui
www.EngineeringMetallurgy.com
RE: How do I increase uniform elongation without losing yield strength in 5754-O?
As for thermal treatments, my anneal practices are limited to batch process (continuous annealing would be ideal, I believe), but perhaps there is more I can do there. I've thought about raising the anneal temperatures, but will it help? Isn't there an increased risk of grain growth at higher temperatures (say above 650F)? Would there be a benefit?
RE: How do I increase uniform elongation without losing yield strength in 5754-O?
In addition to the above recommendation regarding reducing grain size, the technical paper below may be of interest to you especially if you are making your own heats of AA 5754, and can optimize your alloying to achieve desired results;
http://iranscholars.org/wiki/images/8/87/RezaRoumi...
RE: How do I increase uniform elongation without losing yield strength in 5754-O?
1. Increase the amount of cold reduction prior to annealing. The increased dislocation density due to cold working will improve the recrystallization behavior. You already noted the problem of splitting the cold reduction over two passes with an intermediate anneal.
2. Recrystallization is also affected by the size, distribution, and volume fraction of dispersoid particles that are present in the hot-rolled coil. I'm assuming that you are using direct chill cast ingots (Aleris Lewisport, KY?) rather than strip cast product. What are you doing for homogenization prior to hot rolling? Have you evaluated the microstructure at this stage? Non-uniformity of the dispersoids will create excessive microstructural variation.
3. What are the composition levels of Mg, Cr, Mn, Sc, and Zr? All of these exert an influence either on dispersoid formation or solid solution strengthening, and hence final formability. I couldn't open metengr's link, but I am assuming it addresses some or all of these elements.