Strain rate sensitivity and deformation mechanism of nano-lamellar γ-Ni/Ni_5Zr eutectic at room temperature

摘要

The strain rate sensitivity (m) of (Ni_(0.92)Zr_(0.08)_(100-x)Al_x, (0≤x≤4 at.%) eutectic with varying average lamellae thickness (λ_w) in the range of 39-275 nm has been investigated in the strain rate range of 8×10~(-5)and 8 × 10~(-3) s~(-1) at room temperature. The microstructure of the nano-/ultrafine eutectic composites (NECs) is comprised of alternate lamellae of fcc γ-Ni and Ni_5Zr along with 20-31 vol% γ-Ni dendritic phase. The m value of all the investigated NECs lies between 0.0080 and 0.0102, whereas the activation volume (V*) has been estimated to be between 29.7b~3 and 49.8b~3. High-resolution transmission electron microscopy studies confirm the dislocation-mediated plastic flow including dislocation-lamellae interaction, and their pile-up at the interface, which result in the narrow variation of m for a wide range of λ_w due to its interlocked lamellar microstructure. A mathematical model has been developed to correlate the m with λ_w for the experimented NECs with wide microstructure length scale and solute content.