Temperature dependence of plastic flow, anisotropy and ductile fracture

As one of the most common extrinsic features, temperature has an essential impact on the mechanical properties as well as the controlling mechanisms of materials. Therefore, it is aimed in this study to investigate the effect of temperature on the mechanical properties of several steels in an extensive temperature range from -150 °C to 300 °C. Three basic and essential mechanical properties are considered, the plastic flow behavior, anisotropy, and ductile fracture behavior. The temperature influence on plastic flow behavior has been well studied in the literature. With this broad temperature range in the current study, we intend to create a large database to characterize the material behavior as well as to reveal the deformation mechanism change from low to high temperatures. Except for the typical dislocation slipping, the other possible involved mechanisms are twinning and dynamic strain aging. In addition to this, we are particularly focusing on the temperature effect on anisotropy, which has been not covered yet by the existing literature. Based on the experimental results for two pipeline steels, it is shown that the temperature effect on anisotropy could be negligible or significant, depending on the materials. There have been also many investigations of the effect of strain rates on the ductile fracture; however, the temperature effect has not received obvious attention yet. In this study, we set the scope to quasi-static loading condition but vary the loading temperature from -50 °C to 300 °C. The stress-state influence under these temperatures is also considered by employing various sample geometries. Two automotive steel sheets are employed for this study and the results show that a strong temperature effect on the ductile fracture exists for the elevated temperature mainly due to the dynamic strain aging effect, while the less pronounced but non-negligible effect of the temperature is revealed for the lowered temperatures.