Effect of boron addition on the microstructure and mechanical properties of refractory Al0.1CrNbVMo high-entropy alloy. (November 2021)

• Record Type: Journal Article
• Authors: Kang, Byungchul; Kong, Taeyeong; Dan, Nguyen Huy; Phuong, Doan Dinh; Ryu, Ho Jin; Hong, Soon Hyung
• Is Part Of: International journal of refractory metals & hard materials. Volume 100(2021)
• Publication Date: 2021-11
• Subjects: High-entropy alloy -- Refractory high-entropy alloy -- Powder metallurgy -- Boron -- Grain boundary segregation; Heat resistant alloys -- Periodicals; Refractory materials -- Periodicals; Metallography -- Periodicals; Alliages réfractaires -- Périodiques; Matériaux réfractaires -- Périodiques; Métallographie -- Périodiques; Heat resistant alloys; Metallography; Refractory materials; Periodicals; Electronic journals; 669.73
• DOI: 10.1016/j.ijrmhm.2021.105636
• Languages: English
• ISSNs: 0263-4368

Abstract

Abstract: The effect of boron (B) addition on the microstructure and mechanical properties of a refractory high-entropy alloy (RHEA) was investigated. The Al0.1 CrNbVMo RHEA was doped with 0.015 at.% of B by the powder metallurgical process, and its mechanical properties were compared with undoped RHEA. The microstructures of the undoped and doped RHEAs consisted of a single body-centered cubic matrix phase with homogeneously distributed Al2 O3 inclusions. The doped B atoms segregated along grain boundaries and did not form any boride phases. Boron segregation at the grain boundaries was characterized by atom-probe tomography. Compared with the undoped RHEA, the B-doped RHEA showed improved yield strength of 2933 MPa (15% improvement) and ductility of 25.9% (26% improvement). Adding B transformed the fracture surface from intergranular to transgranular due to enhanced grain boundary cohesion induced by B segregation, which resulted in improved ductility. Quantitative analysis was conducted on the undoped and doped alloys to investigate the effect of B on yield strength. The improved yield strength resulting from B doping was attributed to the combined effects of Orowan, dislocation, and B interstitial strengthening. This work demonstrates that B doping of RHEAs is a promising way to overcome their limited room temperature ductility, while maintaining excellent strength. Highlights: Effect of boron doping to BCC-based RHEA was firstly confirmed. Segregation of boron along grain boundaries was clearly observed by APT. The boron doping enhanced both strength and ductility of Al0.1 CrNbVMo RHEA. The boron-doped alloy exhibited an exceptional strength–ductility combination. Comprehensive analysis on the strengthening mechanism was conducted.