Investigation on microhardness distribution of HPT-consolidated pure aluminum powder disks and study on the reason of their high thermal stability

The high pressure torsion (HPT) is a good and effective method for consolidation of different powders by combination of high imposed pressure during torsional straining. In the presentinvestigation, commercial pure aluminum powder were consolidated to dense disks by means of HPT process under 600 kN applied force and 1, 2 and 4 number of turns. For comparison, a few samples were also produced by simple uniaxial pressing -HPT-consolidated samples were annealed under argon atmosphere at 350,450 and 550 C for 1 hour. The microhardness test wascarried out on the cross section of disks on the distance of 0.3 mm along the diameter and thickness for as-fabricated and annealed disks. The data of microhardness were plotted in colorcodedcontour maps of microhardness for each sample. The results showed that by increasing number of turns and distance from the center of disks, the value of microhardness increases. The microhardness distribution for simple compacted disks was uniform the trend of microhardness distribution was unchanged up to 450 for sample processed with 4 number of turns that implies to the high thermal stability of HPT-consolidated disks. By increasing annealing temperature up to 550 C, the microhardness values decreases and the maps transformed to uniform distribution

Keywords:

Severe plastic deformation (SPD) , high pressure torsion (HPT) , color-coded contour maps , microhardness distribution , high thermal stability , powder metallurgy