Macrocrack propagation with grain growth on transient heat loaded tungsten

The propagation of microcrack and grain growth in tungsten occurred at condition of transient heat loads was investigated experimentally, observing the effect on macrocrack development induced by stress intensification in time order. The temperature variation in short time, with frequency 30 Hz, heat flux 0.1 GWm⁻², duration 2 ms at base temperature 1150 °C, induces fatigue fracture on the surface of tungsten, resulting in the formation of microcrack. Since the effective spatial temperature variation is limited to a few micron, microcrack is also occurred at the comparable depth. Following the initiation of microcrack, the grain growth propagation depth over time is measured and calculated based on the grain growth model with measuring the associated constants of the model. Within the grain growth layer, the degraded material properties at the microcrack tip lead to stress intensification which ultimately develop into macrocrack with order of millimeters. The study investigates that the subsurface microstructural changes in tungsten, caused by transient heat loads, have the potential to develop into macrocrack that extend into the deeper bulk area.