Heat transfer in three blocks

Hello.

I have side-by-side three blocks of three difference materials. I want to explore the heat transfer in these blocks when applying a temperature on the surface between the first and second walls. I encounter the following problem.
Heat transfers through the first and second blocks, but it doesn't penetrate into the third block, because it's material is different. When I make the material of the first and third blocks the same, it works fine.
What can I do in this case?

Thanks is advance.