Impact characteristic and crack propagation mechanisms of large-size molybdenum alloy single crystal and polycrystal. (September 2022)

• Record Type: Journal Article
• Authors: Jiao, Benqi; Zhao, Qinyang; Zhao, Yongqing; Zhang, Wen; Li, Yanchao; Hu, Zhongwu; Gao, Xuanqiao; Cui, Changxing; Xin, Tian
• Is Part Of: International journal of refractory metals & hard materials. Volume 107(2022)
• Publication Date: 2022-09
• Subjects: Large-size single crystal -- Molybdenum alloy -- Impact toughness -- Crack propagation -- Cross-slip; 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.2022.105871
• Languages: English
• ISSNs: 0263-4368

Abstract

Abstract: The impact characteristic and crack propagation mechanism for large-size Mo3Nb single crystal with a diameter of about 30 mm have been investigated and disclosed comprehensively by Charpy impact test. The fracture analysis shows that the single crystal crack propagates radially, resulting in a multi-step distribution on the fracture surface. The fracture of Mo3Nb polycrystal is composed of cleavage and quasi-cleavage, exhibiting a trans-granular fracture feature. The impact toughness of single crystal shows orientation dependence, which is attributed to the crack propagation path. Compared with the straight path, the waved path can delay the crack propagation and absorb higher impact energy. The impact toughness of Mo3Nb single crystals is lower than that of Mo3Nb polycrystal at room temperature because the single crystal lacks the coordinated deformation of grain boundary. The analysis of dislocation arrangement for Mo3Nb single crystal shows the different crack propagation paths is caused by the mobility of screw segments, which are controlled by the double cross-slip multiplication mechanism. However, the waved fracture morphology of Mo3Nb polycrystal is caused by the effect of grain boundaries instead of the cross-slip of screw dislocation. Graphical abstract: Unlabelled Image Highlights: The impact toughness of molybdenum alloy single crystal shows orientation dependence The single crystal crack propagates radially and exhibits a multi-step distribution feature. Different crack propagation paths are caused by the mobility of screw segments