Internal/Compressive stress in a material

Hello everyone,

I have a question about internal stress generation in Comsol.

My model consists of two different materials on top of each other. One of the materials (the most outside material in the figure I included) is undergoing an internal compressive force (say it's isotropic) because of oxidation due to oxygen absorption. I am not concerned with the diffusion at this point. The other material (the inner material in the figure I included) is not undergoing the same stresses because it is not oxidizing. The outermost boundary of the outer-layer is considered "free," and is not constrained. I would like to see the stress of the top layer due to the internal stress generation. How would I do this?

Thanks for your help on this very beginner-like question,
John