Maybe what I suggested above is not what you want. In what state do the two materials have zero stress?
Here is a thermal example. Let's say you heat up a flat sheet of glass to a high temperature, then a silver metal coating is plasma deposited on the surface to make a mirror. Let's assume that the coating of sliver has zero stress as it solidifies, and the glass also has zero stress at that high temperature.
Now let the silver coated glass sheet cool down. As the temperature is reduced, stress develops at the interface between the glass and the silver due to the difference in the thermal expansion coefficient. ANSYS can model this by setting the environmental temperature to that high value, then apply a thermal condition of room temperature. The materials will develop a coating stress during the simulation in one step. The solver knows how to apply temperature, so this thermal model is easy to do.
Not pushing on something is hard to simulate. There is something called Inverse Solving that may be what you want. That is where you take a model such as your block with 6 GPa on it, and request a solution that shows the shape of the part when 0 GPa is applied.
Read the ANSYS Help, Mechanical APDL, Structural Analysis Guide, Chapter 8.7 on Inverse Solving.
That starts with the deformed shape with a known load and solves for what the shape of the part is with no load.

Open ANSYS Help and copy the URL below, then paste that into the address of the browser running ANSYS Help.