Modeling the Effect of Diffusion Layer and Interface on the Flow Stress for a Ni/Al Laminate Prepared by Vacuum Hot Pressing

During the forming-reaction integrated process of NiAl alloy thin-walled components, Ni/Al laminates exhibit a complicated deformation behavior. In the present study, a physical-based constitutive model for the preparation of an Ni/Al laminate by vacuum hot-pressing was developed, with consideration of the load-bearing effect and microcracks in the diffusion layers, interface strengthening, and back stress strengthening. The load-bearing effect of the diffusion layer and interface strengthening increased the overall flow stress of the Ni/Al laminate, but did not affect the strain hardening rate. Multiple microcracks in the diffusion layer result into a gradual increase in the strain-softening effect. Unlike in other metal laminates, back stress only exists in the Al layers of an Ni/Al laminate. A gradually increasing back stress can significantly increase the flow stress and strain hardening rate at a strain of less than 0.085, and a gradually decreasing back stress leads to a reduction in the strain hardening rate. Ni/Al laminates with diffusion layers of various thicknesses was used to further verify the robustness of the constitutive model.