Dynamic fracture toughness of a Ti-45Al-1.6Mn alloy at high temperature

Dynamic fracture toughness of a reactive sintered gamma -base TiAl alloy is studied in the temperature range from 298 to 1073 K, The stop block method is employed in order to observe the crack paths and microcrack distributio n ahead of a main crack tip under dynamic loading conditions at high temper ature. Fracture surface, crack path, and microcrack observations are carrie d out using a scanning electron microscope (SEM). Microcrack initiation cri teria and crack-tip stress shielding effect caused by crack deflection are discussed. The experimental results demonstrate that the dynamic fracture t oughness, J(Id). increases with increasing temperature, and after attaining the maximum value at 873 K, the toughness decreases. Crack path morphology varies with temperature. The stress shielding effect at the crack tip caus ed by main crack deflection was found to affect the difference in crack ext ension energy for each temperature. The number of microcracks ahead of a ma in crack varies with temperature. The stress shielding effect at the crack tip caused by microcracking was found to contribute to toughening around 87 3 K.