Microplasticity behavior of porous nickel

We have used a physical and structural approach to study the mechanical beh avior of monoporous (Theta = 5-45%) and biporous (Theta = 45-70%) nickel po wder at room temperature within the strain range 10(-5) to 5.10(-3). We hav e shown that for both low porosity and high porosity materials, the true mi croyield curves depend on the hardening provided by grain boundaries or int erparticle boundaries. We found effects connected with the geometrical stru cture of the materials under investigation. The increase in the deforming s tresses in the base metal material when the porosity is greater than 25% ca n be explained by the peculiarities of the stress states in the interpartic le 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.