Microstructure analysis of high-temperature tensile strength of C276 alloy

C276 alloy exhibits an excellent high-temperature tensile strength at 500-650°C. Optical microscope, scanning electron microscope and X-ray diffraction were used to investigate strengthening mechanisms of C276 alloy. The results show that the yield strength of the specimens does not always decrease with the increasing grain size, which does not match Hall-Petch relation of the grain size strengthening. In addition, some deformation twins and very few precipitated phases are observed in the grains. It can be concluded that good high-temperature tensile strength of C276 arises from co-effects of main solid solution-strengthening and possible deformation twin-strengthening, but not fine grain strengthening and precipitation-strengthening.