Microplasticity behavior of porous nickel

We have used a physical and structural approach to study the mechanical behavior of monoporous (Theta = 5-45%) and biporous (Theta = 45-70%) nickel powder at room temperature within the strain range 10(-5) to 5.10(-3). We have shown that for both low porosity and high porosity materials, the true microyield curves depend on the hardening provided by grain boundaries or interparticle boundaries. We found effects connected with the geometrical structure of the materials under investigation. The increase in the deforming stresses in the base metal material when the porosity is greater than 25% can be explained by the peculiarities of the stress states in the interparticle connections. The softening effect, which depends mainly on the porosity of the powder subsystem, is related to initiation of cracks in the initial phases of microyield.