The effect of temperature over the range of ambient to 704 °C and strain rate from 10⁻⁴ to 10⁻² s⁻¹ on the tensile properties and fracture behavior of ATI 718Plus was investigated. The results showed that with increase in temperature at a strain rate 10⁻⁴ s⁻¹, there is a small reduction in the yield strength, but a large drop in ductility at 704 °C. This reduction was accompanied by a change in fracture mode from ductile transgranular to brittle intergranular cracking. Detailed analysis of the microstructure and microchemistry of the areas around the crack using electron microscopy showed that the driving mechanism behind the failure at elevated temperatures and slow strain rates is oxygen-induced intergranular cracking, a dynamic embrittlement mechanism. In addition, the results suggest that the δ precipitates on the grain boundaries tend to oxidize and may facilitate the oxygen-induced intergranular cracking. Finally, an increase in strain rate at 704 °C caused a small increase in the yield strength and a huge increase in ductility. This increase in ductility was accompanied by a change in fracture mode from brittle-to-ductile failure. Possible mechanisms for the deformation, failure mechanisms, and strain rate dependence are discussed.

研究了温度在环境温度至 704°C 范围内和应变速率从 10 ^-4到 10 ^-2 s ^-1对 ATI 718Plus 的拉伸性能和断裂行为的影响。结果表明，随着温度的升高，应变速率为 10 ^-4 s ^-1, 屈服强度略有下降，但在 704 °C 时延展性下降很大。这种减少伴随着断裂模式从韧性穿晶开裂到脆性晶间开裂的变化。使用电子显微镜对裂纹周围区域的微观结构和微观化学进行详细分析表明，在高温和低应变速率下失效的驱动机制是氧诱导的晶间裂纹，这是一种动态脆化机制。此外，结果表明晶界上的 δ 析出物倾向于氧化并可能促进氧诱导的晶间开裂。最后，在 704 °C 时应变速率的增加导致屈服强度的小幅增加和延展性的巨大增加。这种延展性的增加伴随着从脆性破坏到延性破坏的断裂模式的变化。讨论了变形的可能机制、失效机制和应变率相关性。