Application of a Composite Model in the Analysis of Creep Deformation at Low and Intermediate Temperatures
The creep behaviors of TA2 and R60702 at low and intermediate temperature were presented and discussed in this paper. Experimental results indicated that an apparent threshold stress exhibited in the creep deformation of R60702. Meanwhile, the primary creep phase was found as the main pattern in the room temperature creep behavior of TA2. Compared with exponential law, the power law has been proved to be a proper constitutive model in the description of primary creep phase. It also showed that θ projection method had its significant advantage in the evaluation of accelerated creep stage. Thus, a composite model which combined power law with θ projection method was applied in the creep curves evaluation at low and intermediate temperature. Based on the multiaxial creep deformation results, the model was modified and discussed. A linear relationship existed between composite model parameters and applied load. Finally, the creep life could be accurately predicted and the composite model method is suitable for application in low and intermediate temperature creep life analysis.
Influence of sequential room-temperature compressive creep on flow stress of TA2
This paper studied the sequential room temperature compressive creep and its effects on compressive properties of TA2 with stress-control loading pattern by using cylindrical compressive test specimen. The significant time-dependent deformation under constant load was observed in the TA2 at room temperature, and the deformation was dependent on the loading process under the same loading stress rate. It was also found that the occurrence of room temperature compressive creep obviously enhanced the subsequent yielding strength and flow stress of TA2 due to the increase of network dislocation density. And the effects of room temperature creep on the strain rate-stress behavior could be explained by the local mobile dislocation density model.
Analysis of carbides formed during accelerated aging of 2·25Cr–1Mo steel
Abstract Power-generating plants require materials that can withstand service conditions up to 100 000 h. It is well established that creep properties are controlled by the microstructure and that the microstructure changes during creep service. Accelerated aging was used to obtain a series of simulated microstructures similar to those observed in specimens after long-time service. Electron microscopy was used to monitor the microstructural changes in the specimens. Energy-dispersive X-ray analysis was performed on carbon extraction replicas in a transmission electron microscope. The analysis was combined with an in situ electron diffraction identification of the crystal structure of the carbides present. The authors concluded that accelerated thermal aging can produce simulated service microstructures and that it is possible to distinguish between the cubic carbide M6C and M23C6 using the X-rays generated in these crystals by the electron beam. Thus a comprehensive study of carbide formation and composit...