Thermal stress relaxation behavior in thin films under transient laser-pulse heating

Transient laser pulse has been used to generate nonsynchronous change of temperature rise and thermal expansion in thin films. The transient process of thermal expansion is recorded by a photoelectric high-speed acquisition system. By comparison of the calculated temperature rise and thermal expansion, thermal stress relaxation processes in Al films of 20–50 μm thickness is obtained. This result shows that, for transient heating, thermal stress exists even in the case of uniform temperature distribution and free expansion. And also there is a transient high stress in thin films under high-speed heating.