Effect of temperature on tensile behavior, fracture morphology, and deformation mechanisms of Nickel-based additive manufacturing 939 superalloy

In the current work, uniaxial tensile tests, including interrupted tests at room temperature, intermediate temperatures (650 degrees C and 700 degrees C), and high temperatures (850 degrees C and 950 degrees C), were conducted on the additive manufacturing 939 superalloy to investigate the mechanical properties, fracture behaviors, and deformation mechanisms. According to the experimental results, the tensile mechanical properties exhibit a significant temperature sensitivity, as the yield, tensile strength, and elongation decrease with the increase in temperature. The fracture surfaces show that the material exhibits obvious plastic fracture characteristics at room temperature. Moreover, many multi-slip system steps can be observed when the temperature rises. Furthermore, according to the result of the transmission electron microscopy, the deformation mechanism at room temperature is primarily controlled by the single slip system. As temperature rises to the intermediate temperature region, more slip systems are activated by thermal energy, which promotes the movement of dislocations. The deformation mechanism is mainly dominated by dislocation shearing gamma'. When the temperature reaches the high temperature region, the deformation mechanism firstly demonstrates large-scale stacking faults, and then transforms into the dislocation by-passing and climbing mechanism. Finally, the relationship between temperature and the deformation mechanism is discussed and deduced.

Automated summary

In this study, uniaxial tensile tests were conducted on additive manufacturing 939 superalloy at various temperatures to investigate its mechanical properties, fracture behaviors, and deformation mechanisms. The experimental results showed a significant decrease in yield, tensile strength, and elongation with increasing temperature. The fracture surfaces exhibited plastic fracture characteristics at room temperature and multiple slip systems were observed at higher temperatures. The deformation mechanism was primarily controlled by single slip system at room temperature, while thermal energy activated more slip systems and promoted dislocation movement at intermediate temperatures, and large-scale stacking faults and dislocation by-passing and climbing mechanisms were observed at high temperatures.