You are confusing the reason for tempering metal. Tempering relieves the internal crystal stresses in the metal, not between parts. When heat treating steel for example the crystal formation switches from cubic centered to face centered, during the process many of the carbon atom gets squeezed part way through and many crystals are stressed, this creates a hard but very brittle steel. Tempering allows the atoms to fully align and relieves the atomic level stresses. There are no stresses between parts which heat cycling relieves.