Effect of layer hardness ratio on strength and toughness of Cu-Be/Cu layered composite materials with heterostructure

The Cu-Be/Cu layered heterogeneous composite materials with different layer hardness ratios (R_Cu-Be/Cu=3.0, 5.0, 7.0) were prepared by vacuum hot pressing bonding, cold rolling and subsequent heat treatments. The effects of R_Cu-Be/Cu with different interlayer hardness ratio on the balance of strength and ductility and the strain hardening rate of the composites were investigated. Furthermore, the effect of heterogeneous deformation induced (HDI) hardening on the strain hardening behavior of composites with different R_Cu-Be/Cu was also studied. The results show that the ultimate tensile strength increases and the uniform elongation decreases with the increase of the interlayer hardness ratio. However, the ultimate tensile strength of the composites is higher than the value calculated by the rule of mixture (ROM). Moreover, the uniform elongation is also higher than that of the corresponding Cu-Be component, among which the composites with R_Cu-Be/Cu of 5.0 possess the best balance of strength and ductility. The extra strain hardening effect in the layered composite materials with heterostructure can be caused by HDI hardening. The effect of HDI hardening on strain hardening is relatively weak in the composites with R_Cu-Be/Cu of 3.0, while the HDI hardening in the composites with R_Cu-Be/Cu of 7.0 reaches saturation at the initial stage of plastic deformation and then decreases rapidly. The HDI hardening in the composites with R_Cu-Be/Cu of 5.0 plays a dominant role during the strain hardening process and provides the extra strain hardening effect for the composites within a large strain range.