HIGH-TEMPERATURE FATIGUE CRACK GROWTH RESISTANCE OF THERMO-MECHANICALLY AND HEAT TREATED CAST Ti-Si-Al-Zr COMPOSITES

摘要

Fatigue crack growth resistance of Ti-4Si-4Al-5Zr composites have been investigated at room and elevated (500 °C, 700 °C and 800 °C) temperatures. Various modifications were manufactured with electron-arc smelting, the thermo-mechanical deformation (of 41 % and 90 %) and heat treatment (quenching). It was found that the high-temperature effect on the crack growth in the materials tested is negligible in threshold (ΔK_(th)) and critical (ΔK_(fc)) regions of the da/dN-ΔK diagram and the maximum acceleration of the crack growth occurs in the middle ΔK region. The satisfactory fatigue crack growth resistance at temperatures of 500 °C and 700 °C has been observed in thermodeformed modifications but thermo-mechanical treatment causes the increase in fatigue crack growth resistance at high ΔK level and its decrease at low ΔK level. Microstructure and failure micromechanisms have been analysed in accordance with crack growth resistance of the composites.