Correlation between the microstructures and the deformation mechanisms of CuZr-based bulk metallic glass composites

Abstract

The variation of the transformation-mediated deformation behavior with microstructural changes in CuZr-based bulk metallic glass composites is investigated. With increasing crystalline volume fraction, the deformation mechanism gradually changes from a shear-banding dominated process as evidenced by a chaotic serrated flow behavior, to being governed by a martensitic transformation with a pronounced elastic-plastic stage, resulting in different plastic deformations evolving into a self-organized critical state characterized by the power-law distribution of shear avalanches. This is reflected in the stress-strain curves by a single-to-“double”-to-“triple”-double yielding transition and by different mechanical properties with different serrated flow characteristics, which are interpreted based on the microstructural evolutions and a fundamental energy theorem. Our results can assist in understanding deformation behaviors for high-performance metastable alloys

Deformation-Induced Martensitic Transformation in Cu-Zr-Zn Bulk Metallic Glass Composites

“…For the samples with low Zn contents of 0, 1.5, and 2.5 at. %, the dominating phase is CuZr martensite, being similar to previous reports [19][20][21][22][23][24][25][26][27]. Additionally, a small quantity of B2 CuZr phase being accompanied with minor Cu10Zr7 crystals can be observed in the matrix.…”

“…Until now, CuZr-and TiNiCu-based alloy systems with different compositions have been fabricated into BMG composites [19][20][21][22][23][24][25][26][27][28]. For example, CuZr-based BMG composites with different sample sizes containing minor element additions such as Al, Ti, Ag, Ni, Co, Y, Er, V, W, or Ta have been successfully fabricated [20][21][22][23][24][25][29][30][31][32][33][34][35][36][37].…”

“…Recently, it has been found that, by introducing a shape memory ductile phase into the glassy matrix, the fabricated BMG composites show not only a pronounced tensile ductility but also a macroscopic work-hardening capability during deformation at room temperature [19][20][21][22][23][24][25][26][27]. Upon loading, besides the formation of multiple shear bands in the glassy matrix, ductile shape memory crystals experience the martensitic transformation (MT) from a cubic phase to monoclinic phases [19][20][21][22][23][24][25][26][27], which can provide the pronounced work hardening.…”

“…Upon loading, besides the formation of multiple shear bands in the glassy matrix, ductile shape memory crystals experience the martensitic transformation (MT) from a cubic phase to monoclinic phases [19][20][21][22][23][24][25][26][27], which can provide the pronounced work hardening. Hence, the weakness of the work-softening effect during deformation of BMG composites can be effectively overcome.…”

“…For example, CuZr-based BMG composites with different sample sizes containing minor element additions such as Al, Ti, Ag, Ni, Co, Y, Er, V, W, or Ta have been successfully fabricated [20][21][22][23][24][25][29][30][31][32][33][34][35][36][37]. Two key requirements should be satisfied for the fabrication of CuZr-based BMG composites: (1) maintaining sufficiently high glass-forming ability (GFA) in order to fabricate large-sized BMG composites [20][21][22][23][24][25][29][30][31][32][33][34][35][36][37]; and (2) stabilization of metastable B2 CuZr phase in order to suppress its decomposition into equilibrium phases (EPs) [29][30][31][32][33][34]. Previous results [22,38] demonstrated that minor Co addition to CuZr alloys can dramatically enhance the thermal stability of the B2 CuZr phase but gravely deteriorate the GFA of CuZr-based alloys.…”