Dual-plex Grain Structure (A286 parts)

Hello, Group. Here's the micro-structure photograph of the A286 special locknut we manufacture. You can see that the grain sizes are
all over the place; what could be the cause? Contaminants inthe material? Improper heat treating? These parts were solution treated and then aged per customer specs. The material came from Carpenter Technology. TIA, Dave Griffith Monterey Machine Products For micro-structure photo please go to:
http://i34.photobucket.com/albums/d146/rattmanndoo/DSCN5052.jpg
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monterey machine wrote:

I give Carpenter a call
cheers Bob
let us know the outcome
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I'm not familiar with this alloy but here's a guess. Looks like the grain size is finer in the thread area. Is it possble this area get cold worked more before heat treat and when heat treating happens and grain structure recrystallizes into finer gains? The area in the center looks coarser - could it be a delayed transformation area due to the time it takes to remove hear from that area.
Mark

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How were the threads cut and the other side cut ? - was it kept cool really cool or did it heat up and zonal migrate or zonal structurize ?
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member http://lufkinced.com /
BobK207 wrote:

-
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Martin H. Eastburn wrote:

The parts were machined from aged bar stock (we had it aged, we didn't buy it in aged condition). The threads were single-point cut. The part is a nut so the threaded part is the inner part of the bar. The grain structure on this inner part looks fine but there's duplex grain structures on the outside. See photo at:
http://i34.photobucket.com/albums/d146/rattmanndoo/DSCN5052.jpg
Dave MontereyMachine Products
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