Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : December 22, 2018 - December 24, 2018
High entropy alloys(HEAs), including a large amount of solid solution elements, have not only high capability of solid solution strength but great strength-ductility balance and high fracture resistance. Although mechanical properties of HEAs except for fatigue are reported, there are few reports on fatigue properties. Because fatigue fracture accounts for about 80% of accidents in structural materials, understanding of the fatigue properties of HEAs is the most important task for practical use. In this research, fatigue crack growth characteristics of an Fe20Cr20Ni20Mn20Co (at.%) high entropy alloy were investigated by ΔK increasing compact tension testing in comparison with a SUS316L. Fatigue crack growth rate of the HEA was lower than that of the SUS316L, irrespective of ΔK. The main crack growth path of both alloys was grain interior and a difference between two alloys was found to be in the roughness of the crack growth path. The roughness of the fatigue crack growth path of the HEA was larger than that of the SUS316L. This fact indicates that the HEA has larger roughness-induced crack closure effect than the SUS316L, which causes low fatigue crack growth rate of HEA. Another key is a non-crystallographic transgranular crack growth mechanism. The main crack path of the SUS316L was straight so the SUS316L shows crack growth via crack blunting/re-sharpening, while the HEA shows transgranular crack growth associated with dislocation substructure alignment, resulting in the relatively rough.
