Why Do Metals Like Fe-C Show Upper and Lower Yield Points?

[aero&astro]

Why do Fe-C and other metals exhibit upper and lower yield points?

And also can you get substitutional solid solution in any Fe-C metals, like ferrite, austenite etc?

 

[Mapes]

Why do Fe-C and other metals exhibit upper and lower yield points?

Answered https://www.physicsforums.com/showpost.php?p=2605350&postcount=8".

And also can you get substitutional solid solution in any Fe-C metals, like ferrite, austenite etc?

Sure, I can't see why not.