A study of stress-induced phase transformation and micromechanical behavior of CuZr-based alloy by in-situ neutron diffraction

Abstract

The stress-induced phase transformation and micromechanical behavior of CuZr-based alloy were investigated by in-situ neutron diffraction. The pseudoelastic behavior with a pronounced strain-hardening effect is observed. The retained martensite nuclei and the residual stress obtained from the 1 st cycle reduce the stress threshold for the martensitic transformation. A © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ critical stress level is required for the reverse martensitic transformation from martensite to B2phase. An increase of intensity for the B2 (110) plane in the 1 st cycle is caused by the twinning along the {112}<111> twinning system. The convoluted stress partitioning influenced by the elastic and transformation anisotropy along with the newly formed martensite determines the microstress partitioning of the studied CuZr-based alloy. The reversible martensitic transformation is responsible for the pseudoelasticity. The macro mechanical behavior of the pure B2 phase can be divided into 3 stages, which are mediated by the evolvement of the martensitic transformation.The poor plasticity of conventional Bulk Metallic Glasses (BMGs) due to the highly localized shear bands has limited their engineering applications [1][2][3][4][5][6], although BMGs are one of the potential candidates for engineering structural materials due to their high strength, high hardness, and high wear resistance etc [7][8][9][10][11][12]. Recent efforts showed the poor plasticity could be adjusted 3 by introducing crystalline phases into the glass matrix, i.e. Bulk Metallic Glass Composites (BMGCs). The composites can possess the plastic deformability up to about the total 22% compressive strain [19]. However, to accommodate plastic strain, a series of ZrTi-based and Tibased composites show the obvious work softening after yielding, which restrict their practical engineering applications [16,[20][21]. In contrast, excellent work hardening has been achieved in the CuZr-based BMGCs [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41]. As a result, the CuZr-based BMGCs containing B2 crystallites have garnered much interest owing to their outstanding work hardening ability.Recently, efforts have been taken to explain the mechanical behavior of the B2 crystalline in the CuZr-based BMGCs by ex-situ characterization methods, including X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), etc. For example, for the nano-sized B2 CuZr crystals, the precipitation [6,22,24,28,33] as well as the twinning of these nanocrystals [6] provides an effective way to counteract the strain softening. For the microsized B2 CuZr crystals, Pauly and Eckert [30][31] believe the compatibility of the elastic properties of the B2 phase and the amorphous matrix promotes the slip to transfer from the amorphous matrix to the B2 phase. Moreover, the B2 phase in BMGCs upon loading can also undergo martensiti...

Event-based processing of neutron scattering data at the Spallation Neutron Source

“…Combining this chopping with the stroboscopic methodology, VULCAN provides the capability for fast real-time operando testing. Users have benefited from these scientific capabilities and conducted a broad range of new research in materials science and engineering, including stress-induced twin reorientation (Pramanick et al, 2011), phase transformation in shapememory alloys (Yang et al, 2017;Wang et al, 2017) and bulk metallic glass composites (Wu et al, 2017), transformationinduced plasticity in alloys (Yu et al, 2014;Huang et al, 2017), twinning/detwinning behaviors in metals (Wu et al, 2013(Wu et al, , 2014(Wu et al, , 2015Xie et al, 2017;Wu & An, 2016), residual stress relaxation in engineering structures (Aba-Perea et al, 2016), domain switching in oxides (Aman et al, 2014), non-equilibrium phase transformation during rapid heating (Yu et al, 2012), cycling and degradation of realistic-format batteries Wang et al, 2012;Liu et al, 2013Liu et al, , 2016, and in situ materials processing and synthesis (Cai, Liu et al, 2013;Chen et al, , 2014Steiner et al, 2016). Specific examples of the use of event data acquisition are chosen from battery charge-discharge, rapid heating of a dual-phase steel and cyclic fatigue-induced martensitic phase transformation.…”