Analysis of the fatigue crack growth mechanisms in equimolar body centered cubic HfNbTaTiZr high-entropy alloy: Discussions on its singularities and consequences on the crack propagation rate properties

• Published in: Intermetallics 2019-07, Vol.110, p.106459, Article 106459
• Main Authors: Guennec, B., Kentheswaran, V., Perrière, L., Ueno, A., Guillot, I., Couzinié, J-Ph, Dirras, G.
• Format: Article
• Language: English
• Subjects: Crack propagation; Crystallography; Electron backscatter diffraction; Fatigue failure; Fatigue resistance and crack growth; Fracture mechanics; Fracture surfaces; Grain boundary; High entropy alloys; High-entropy alloy; Lower bounds; Mechanical properties; Modulus of elasticity; Planes; Propagation; Singularities; Slip planes; Slip system; Stress ratio; Striations
• ISSN: 0966-9795; 1879-0216
• DOI: 10.1016/j.intermet.2019.04.002

In the present work, the fatigue crack propagation mechanisms of the body centered cubic (BCC) equimolar HfNbTaTiZr HEA are investigated in air and at room temperature. A fatigue threshold ΔKth of 2.5 MPa m1/2 coupled with a slope parameter of the Paris regime m of 2.2 at a stress ratio of 0.1 are reported. The fatigue threshold over elastic modulus ratio ΔKth/E corresponds approximately to the lower bound of the usual range reported for this value among the metallic materials. The fracture surfaces outlined crystallographic fatigue crack propagation mechanism, where the formation of striation patterns having spacing identical to crack propagation rate is noted. The crack path analysis emphasized a crack spreading along both {011} and {112} slip planes. This profusion of planes implies singularities of the crack propagation in comparison with other metallic materials prone to crystallographic crack propagation. [Display omitted] •Fatigue crack growth features of BCC HfNbTaTiZr HEA are investigated.•A Paris regime is detected with a slope parameter of 2.2 from ΔK = 5 MPa m1/2.•Striation pattern on the fracture surfaces are correlated to crack growth velocity.•Crack path is conveyed on both {011} and {112} planes.•The fatigue threshold ΔKth = 2.5 MPa m1/2 induces a ratio ΔKth/E in the usual range.