Showing papers by "S. Sankaran published in 2016"
TL;DR: In this article, X-ray tomography was employed to characterize the geometric structure of cells and found that cell structure with high degree of uniformity evolved in 5TiB 2 composite foams compared with 10 TiB 2 composites for a given holding time.
23 citations
TL;DR: In this paper, a power law creep mechanism involving dislocations is found to be observed in all the compacts sintered at all pressures, which is evident from the TEM micrographs as well.
Abstract: The Al-4.5 wt.% Cu powder was compacted by spark plasma sintering at three compaction pressures namely 30, 40, and 50 MPa maintaining temperature constant at 500°C. Porosity seems to be closed in all the 3 cases. Relative density of S-50 is decreased due to increase in electrical erosion holes. Transmission electron microscopy studies reveal the presence of dislocations in all the compacts and shear bands observed only in the compact sintered at 50 MPa. A power law creep mechanism involving dislocations is found to be observed in all the compacts sintered at all pressures, which is evident from the TEM micrographs as well. The dissolution of Al2Cu precipitates in the aluminum matrix, and the increase in electric erosion holes were noticed with increase in pressure from 30 to 50 MPa. The decrease in the volume fraction of Al2Cu phase and the increase in the formation of electric erosion holes resulted in reduced hardness and compression strengths of the compacts.
7 citations
TL;DR: In this paper, the relationship between cyclic deformation, slip-mode and dislocation structures was investigated in 316LN stainless steel (with 0.07-0.22% Nitrogen) subjected to low cycle fatigue at temperatures in the range 300-873 K and at a 0.6% strain amplitude.
Abstract: The relationship between cyclic deformation, slip-mode and dislocation structures is investigated in 316LN stainless steel (with 0.07–0.22 wt% Nitrogen) subjected to low cycle fatigue at temperatures in the range 300–873 K and at a 0.6 % strain amplitude. Irrespective of the nitrogen content, cyclic softening/saturation occupied a large fraction of fatigue life at temperatures <773 K. The end-of-life dislocation structures (e.g. dislocation cells, planar slip-bands) characterizing the cyclic softening/saturation belong to wavy/mixed/planar slip-modes of deformation. On the other hand at temperatures ≥773 K, similar dislocation structures are noticed to be associated with significant cyclic strengthening with limited softening. The differences in the above deformation behavior is found to be controlled not by the nature of slip-mode but by the consequences of dynamic strain aging occurrence (e.g. significant cyclic strengthening and pronounced serrations) which are noticed to vary in the temperature range 573–873 K. Maximum fatigue life is observed at 0.11–0.14 wt% N that induced mixed mode of deformation.
6 citations