Showing papers by "Bhagwati Prasad Kashyap published in 2009"
TL;DR: In this article, the effect of two-pass overlap friction stir processing on microstructural refinement of Al-30Si alloy was demonstrated, which delineates significant reduction in size and aspect ratio of silicon particles from average 200 to 2µm and 4.93 to 1.75 ǫm respectively.
56 citations
TL;DR: In this paper, the hot deformation behavior of spray formed HIPed Al-Li (UL40) alloy was studied using processing map technique, where the map has been interpreted in terms of the microstructural processes occurring in situ with deformation, based on the values of a dimensionless parameter η which is an efficiency index of energy dissipation through micro structural processes.
54 citations
15 Sep 2009-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the yield strengths of Ti-Al-Nb alloys were found to obey the Hall-Petch relationship with grain size, and the overall friction stress ( σ i o c ) was observed to decrease with increase in Nb content while it remained more or less unchanged with an increase in Al content in these alloys.
Abstract: The yield strengths of Ti–Al–Nb alloys, which undergo stress-induced martensitic transformation, prior to the onset of plastic deformation during tensile testing, were found to obey the Hall–Petch relationship with grain size. The overall friction stress ( σ i o c ) was observed to decrease with increase in Nb content while it remained more or less unchanged with increase in Al content in these alloys. On the other hand, the overall k y o c , the unpinning constant, which is an index of the efficiency of boundaries as obstacle to dislocation motion, was found to increase with increase in Nb and decrease with increase in Al content in these alloys.
29 citations
TL;DR: In this paper, an AA6082 alloy was subjected to eight passes of equal channel angular pressing at 100°C, resulting in an ultrafine grain size of 0.2 to 0.4μm.
Abstract: An AA6082 alloy was subjected to eight passes of equal channel angular pressing at 100 °C, resulting in an ultrafine grain size of 0.2 to 0.4 μm. The tensile deformation behavior of the material was studied over the temperature range of 100 °C to 350 °C and strain rate range of 10−4 to 10−1 s−1. The evolution of microstructure under tensile deformation was investigated by analyzing both the deformation relief on the specimen surface and the dislocation structure. While extensive microshear banding was found at the lower temperatures of 100 °C to 150 °C, deformation at higher temperatures was characterized by cooperative grain boundary sliding and the development of a bimodal microstructure. Dislocation glide was identified as the main deformation mechanism within coarse grains, whereas no dislocation activity was apparent in the ultrafine grains.
23 citations
TL;DR: In this paper, the effect of alloy composition on the fracture toughness of Ti-Al-Nb alloys, which undergo stress-induced martensitic transformation (SIMT), was investigated for a given volume fraction of primary α ≥ 2.
Abstract: The effect of alloy composition on the fracture toughness of Ti-Al-Nb alloys, which undergo stress-induced martensitic transformation (SIMT), was investigated for a given volume fraction of primary α
2. Both Ti-18Al-8Nb and Ti-15Al-12Nb alloys exhibited lower fracture toughness values as compared to Ti-15Al-8Nb alloy, which indicated that higher Al or Nb was detrimental to fracture toughness in these alloys in the presence of primary α
2. The results were explained on the basis of the effect of composition on fracture toughness contributions due to SIMT as well as ductile fracture.
5 citations