Mechanics of single pass equal channel angular extrusion of powder in tubes

In the current study powder in tubes (PITs) are processed through single pass equal channel angular extrusion (ECAE), for two different powders by using three different tube materials. Studies were conducted for the first time to understand the processing mechanism of ECAE of PITs. In the case of hard brittle intermetallic magnesium boride (MgB₂) powder, the process was found to primarily involve compaction and shear-sliding of the powder, and localized-deformation of the tube. Reasons for localized-deformation occurring during ECAE were discussed in detail. Compaction efficiency was understood to depend not only on the material of the tube but also on the homogeneity of stress and strain in the composite PIT. Various frictional stresses and mechanisms of localized-deformation were found to be the reasons for stress-strain inhomogeneity. In the case of copper powder, even though localized-deformation occurred, higher inter-particle friction and low yield strength of the powder helped in the complete densification of the powders. PACS 81.20.Ev; 83.50.-V; 07.10.Pz; 62.20.Fe; 74.25.Ld