Dynamic fracture toughness of a reactive sintered y-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 distribution ahead of a main crack tip under dynamic loading conditions at high temperature. Fracture surface, crack path, and microcrack observations are carried out using a scanning electron microscope (SEM). Microcrack initiation criteria and crack-tip stress shielding effect caused by crack deflection are discussed. The experimental results demonstrate that the dynamic fracture toughness, JId, 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 caused by main crack deflection was found to affect the difference in crack extension energy for each temperature. The number of microcracks ahead of a main crack varies with temperature. The stress shielding effect at the crack tip caused by microcracking was found to contribute to toughening around 873 K.
|ジャーナル||Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science|
|出版ステータス||出版済み - 1 1 2000|
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