Application of systematic scanning and variance analysis method to evaluation of pores arrangement in sintered steel

Abstract

The porosity characteristics of sintered specimens, made of the Distaloy AB powder, subjected to various deformation modes have been examined within the work. The sintering technological parameters were adjusted to obtain 15% volume fraction of pores. The sintered specimens were plastically deformed by conventional uniaxial compression, compression with the cyclic torsion (3°, 0.5 Hz and 6°, 1 Hz), compression with the cyclic transverse motion of the punch and finally compression with the cyclic torsion and superimposed cyclic transverse motion of the punch. The systematic scanning and two-way ANOVA analysis were carried out to describe the spatial arrangement of the porosity in the microstructure before and after deformation. The mean values of pores area fractions were also analysed. Based on the investigation, it was identified that all specimens after plastic deformation are characterized by significantly smaller porosity fraction in comparison with the initial state (as-sintered). The lowest mean area fraction of the pores equal to 4.18% was obtained in the specimen after compression with the cyclic torsion (3°, 0.5 Hz) and with the cyclic transverse motion of the punch. However, in this case, the arrangement of pores in the sample was inhomogeneous. On the contrary, the compression with only cyclic torsion led to the homogenous arrangement of pores. A similar situation was in the case study of compression with only cyclic transverse motion of the punch. However, it was pointed out that the most advantageous, from porosity level reduction and arrangement homogeneity point of view, is the plastic deformation by compression with the cyclic transverse motion of the punch, and without cyclic torsion.