Effect of work hardening discrepancy on strengthening of laminated Cu/CuZn alloys

doi:10.1016/j.jmst.2021.06.043

Abstract

Abstract:

To clarify the work hardening discrepancy effect on the strengthening of laminated metals, we designed two laminated Cu/Cu4Zn and Cu/Cu32Zn samples with different layer thicknesses. Cu/Cu4Zn has larger work hardening discrepancy between two constituent layers relative to Cu/Cu32Zn, but the yield strengths of two CuZn constituents are comparable. Uniaxial tensile results suggest Cu/Cu4Zn with larger work hardening discrepancy exhibits a significant strengthening at early deformation stage while Cu/Cu32Zn possesses a better ductility. The underlying mechanisms for the strengthening effect are attributed to more geometrically necessary dislocations accumulated at interfaces and severer strain localization due to the larger work hardening discrepancy.

Key words: Laminated Cu/Cu alloys, Work hardening, Strengthening, Interfacial affected zone, Strain localization

Zheng Cao, Zhao Cheng, Wei Xu, Lei Lu. Effect of work hardening discrepancy on strengthening of laminated Cu/CuZn alloys[J]. J. Mater. Sci. Technol., 2022, 103: 67-72.

Figures/Tables 6

Fig. 1. Low magnification SEM images of Cu/Cu4Zn (a) and Cu/Cu32Zn (c) with layer thickness of 19 μm. High magnified SEM images of Cu/Cu4Zn (b) and Cu/Cu32Zn (d) as indicated by white boxes in (a) and (b). RD, ND and TD are rolling, normal and transverse directions, respectively.

Table 1 The average grain size, yield strength, uniform elongation and ultimate strength of laminated Cu/Cu4Zn, Cu/Cu32Zn with layer thickness of 19 μm compared to their freestanding constituents Cu, Cu4Zn and Cu32Zn.

Sample	Grain size (μm)	Yield strength (MPa)	Uniform elongation (%)	Ultimate strength (MPa)
Cu	7 ± 0.2	119 ± 6	30 ± 0.6	243 ± 3
Cu4Zn	0.32 ± 0.01	352 ± 1	1.5 ± 0.2	360 ± 2
Cu32Zn	1.7 ± 0.1	341 ± 7	28.8 ± 1.5	448 ± 1
Cu/Cu4Zn(19 μm)	7.5 ± 0.2 (Cu)0.34 ± 0.01 (Cu4Zn)	264 ± 6	13.7 ± 2.5	308 ± 2
Cu/Cu32Zn(19 μm)	4.7 ± 0.2 (Cu)1.2 ± 0.1 (Cu32Zn)	225 ± 2	29.6 ± 0.7	345 ± 2

Fig. 2. Tensile engineering stress-strain curves of freestanding Cu, Cu4Zn, Cu32Zn samples (a), and laminated Cu/Cu4Zn, Cu/Cu32Zn with different layer thicknesses (b). The inset of (a) shows work-hardening rate vs. true strain of freestanding Cu, Cu4Zn, Cu32Zn. (c) The variation of yield strengths of two laminated metals with different layer thicknesses.

Fig. 3. Inverse pole figure mapping colored by transverse-direction (TD) of the Cu/Cu4Zn (a-c) and Cu/Cu32Zn (d-f) samples under different tensile strains of 0% (a, d), 1% (b, e) and 9% (c, f).

Fig. 4. GND density mapping from EBSD measurement of laminated Cu/Cu4Zn (a-c) and Cu/Cu32Zn (d-f) with layer thickness of 19 μm at ε = 0%, 1% and 9%, as indicated. Averaged GND density distributions in Cu layer at different strains of Cu/Cu4Zn (g) and Cu/Cu32Zn (h). TA, tensile axis.

Fig. 5. Distribution of strain along tensile axis, εxx, of Cu/Cu4Zn (a,b) and Cu/Cu32Zn (d,e) with layer thickness of 19 μm at ε = 1% and ε = 3% as indicated. The deformation morphologies on lateral surface of Cu/Cu4Zn (c) and Cu/Cu32Zn (f) deformed at ε= 9%. Shear bands and slip bands are indicated by blue and red arrows, respectively.

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