Anisotropic Compressive Behavior of Zn-22Al Superplastic Alloy Foams Manufactured Powder Metallurgy Process

Closed-cell Zn-22Al alloy foams are produced through powder metallurgy process. Zn-22Al alloy powders and titanium hydride powders were mixed to prepare a precursor. The precursor was manufactured using uniaxial hot pressing. Macro- scopic porosity is as large as 70% in the condition of heating temperature at 873 K for 20 min. Average pore aspect ratio is 0.48 and the pores extended in the direction of perpendicular to hot pressing were observed. Compressive tests were carried out in the different loading axes and crosshead speeds. Plateau stress in the direction of hot pressing was lower than the direction of perpendicular to hot pressing. Anisotropic deformation behavior is due to the anisotropic cell morphology which was induced during the uniaxial hot pressing. In contrast, difference of strain rate sensitivity exponent (m value) in the compressive directions was not observed. This is because the m value does not depend on cell morphology but on cell wall material.