Compressive vs. tensile yield and fracture toughness behavior of a body-centered cubic refractory high-entropy superalloy Al0.5Nb1.25Ta1.25TiZr at temperatures from ambient to 1200°C. (15th February 2023)

• Record Type: Journal Article
• Authors: Kumar, Punit; Kim, Sang Jun; Yu, Qin; Ell, Jon; Zhang, Mingwei; Yang, Yang; Kim, Ji Young; Park, Hyung-Ki; Minor, Andrew M.; Park, Eun Soo; Ritchie, Robert O.
• Is Part Of: Acta materialia. Volume 245(2023)
• Publication Date: 2023-02-15
• Subjects: Multiple principal element alloys -- Superalloys -- Refractory alloys -- High-temperature deformation -- Tensile behavior -- Intergranular fracture; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2022.118620
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: The microstructure of high-entropy alloys with refractory elements and Al as constituents can be considered to be analogous to superalloys. These so-termed refractory high-entropy superalloys (RHSAs) can show remarkable compressive strength up to temperatures exceeding 1200 °C. Here, we examine the microstructure and properties - compressive, tensile, and fracture toughness - of a precipitation-hardened, body-centered cubic, RHSA, Al0.5 Nb1.25 Ta1.25 TiZr, at ambient temperature (RT) to 1200 °C. Two dual-phase microstructures comprising ordered B2 (brittle) and disordered A2 (ductile) phases were produced in this alloy - one with B2 as the matrix, the other with A2 - for evaluation of the mechanical properties. Under compression, both microstructures display RT compressive strengths above 1.5 GPa and considerable ductility exceeding 40% at elevated temperatures; the alloy with the A2 matrix has ∼15% compressive ductility even at RT. However, properties are very different under tensile loading; at all temperatures, both microstructures fail predominately in an intergranular mode in the elastic regime at a fracture stress less than 200 MPa and ductility below 0.15%. The microstructure with the A2 matrix has a K Ic fracture toughness of ∼15 MPa√m at RT, although at all temperatures above 800 °C, measured K Ic values for both dual-phase microstructures are less than 5 MPa√m. In this study, we investigate the microstructural origin of these mechanical properties, and emphasize the importance of evaluating these alloys in tension. Graphical abstract: Image, graphical abstract