Effect of extreme environmental temperature on the fracture resistance, and fatigue behavior of dual phase Ti-6Al-4V alloy
The behavior of materials subjected to extreme environments is a challenging and diverse topic of interest to many researchers. Typically, structural materials in advanced energy systems are subjected to extreme heat, pressure, and radiation fluxes that may promote accelerated degradation. Titanium-based alloys are considered as favorable structural materials for diverse applications in such extreme environments, particularly in nuclear reactors, aerospace, and high temperature applications. In this work, the effect of extreme environmental temperature on the mechanical, fracture resistance, and fatigue behavior of dual phase Ti-6Al-4V alloy was investigated. Rectangular tensile specimens and single edge notched specimens of 75×12.7×0.81 mm were cut along the rolling direction and were exposed to environmental temperatures of 650 °C, and 900 °C for two hours to simulate the extreme environmental conditions. The mechanical and fracture behavior of the materials exposed to these elevated temperatures were evaluated and the result revealed that the tensile strength and fracture toughness of the alloy was dropped significantly by 25%, and 40%, respectively after the exposure to 900 °C from the ambient values. The fracture surface morphology of this alloy displayed strong ductile behavior with dimple features at room temperature, but some voids formed at 900 °C along the grain boundaries with significant ductility loss due to the formation of Ti3Al phase. Microstructural analysis showed that as the temperature increased, the density of retained β grains also reduced in α matrix. The fatigue test showed substantial loss of fatigue life and higher crack growth rate at higher temperatures.