Deformation Behavior of Cold Upset Forming of Sintered Al-Fe Composite Preforms

Abstract

Cold upsetting experiments were carried out on sintered Al–Fe preforms in order to evaluate their deformation characteristics. The effects of iron content and initial fractional density of the preforms on deformation behavior have been investigated thoroughly by using graphite as a lubricant. Cylindrical preforms with different initial theoretical density and aspect ratio (0.75) were prepared using a suitable die, a punch and a die bottom insert on a 1.0 MN capacity Universal testing machine. The preforms were well covered with dry fine silica sand and sintered in an electric muffle furnace at 550±10°C for a period of 1 h and then furnace cooled. Cold deformation experiments were carried out in several steps. Dimensions such as height, contact, and bulged diameters and densities were measured for each test. In general, each compact was subjected to an incremental compressive loading in steps of 0.005 MN until fine cracks appeared on its free surface. Analysis of the experimental data has shown that the power law relationship between fractional theoretical density ρf/ρth and eεz−εθ has been established. This remained valid for 0–8% iron content and all initial preform densities. Further it was found that the preforms of higher iron content shows higher values of deformation properties like the axial stress and the Poisson’s ratio than less/without iron preforms provided that the initial fractional density taken is kept constant.