Showing papers by "Sushanta Kumar Panigrahi published in 2008"

A study on the mechanical properties of cryorolled Al–Mg–Si alloy

Abstract: The mechanical properties of a precipitation hardenable Al–Mg–Si alloy subjected to cryorolling and ageing treatments are reported in this present work. The severe strain induced during cryorolling of Al–Mg–Si alloys in the solid solutionised state produces ultrafine microstructures with improved mechanical properties such as strength and hardness. The improved strength and hardness of cryorolled alloys are due to the grain size effect and higher dislocation density. The ageing treatment of cryorolled Al–Mg–Si alloys has improved its strength and ductility significantly due to the precipitation hardening and grain coarsening mechanisms, respectively. The reduction in dimple size of cryorolled Al–Mg–Si alloy upon failure confirms the grain refinement and strain hardening mechanism operating in the severely deformed samples.

Effect of rolling temperature on microstructure and mechanical properties of 6063 Al alloy

Abstract: Aluminium alloy (6063) was severely rolled upto 92% thickness reduction at liquid nitrogen temperature and room temperature to study the effect of rolling temperature on its mechanical properties and microstructural characteristics by using tensile tests and SEM/electron back scattered diffraction (EBSD), transmission electron microscope (TEM), DSC, X-ray diffraction (XRD) as compared to room temperature rolled (RTR) material with the same deformation strain. An improved strength (257 MPa) of cryorolled 6063 Al alloy was observed as compared to the room temperature rolled alloy (232 MPa). The improved strength of cryorolled alloy is due to the accumulation of higher dislocation density than the room temperature rolled material. The tensile properties of cryorolled alloy and the alloy subjected to different annealing treatments were measured. The cryorolled alloy subjected to annealing treatment at 300 °C for 5 min exhibits an ultrafine-grained (UFG) microstructure with improved tensile strength and ductility.

A Comparative Study on Mechanical Properties of Al 7075 Alloy Processed by Rolling at Cryogenic Temperature and Room Temperature

Abstract: The mechanical properties and microstructural characteristics of a precipitation hardenable Al 7075 alloy subjected to rolling at liquid nitrogen temperature and room temperature are reported in this present work. The Al 7075 alloy was severely rolled at cryogenic temperature and room temperature and its mechanical properties were studied by using tensile tests and hardness. The microstructural characterization of Al 7075 alloy were made using SEM/EBSD, TEM and DSC. The cryorolled Al 7075 alloys have shown improved mechanical properties as compared to the room temperature rolled Al alloy. The cryorolled Al alloy after 90% thickness reduction exhibits ultrafine grain structure as observed from its TEM micrographs. It is observed that the strength and hardness of the cryorolled materials (CR) at different percentage of thickness reductions are higher as compared to the room temperature rolled (RTR) materials at the same strain due to suppression of dynamic recovery and accumulation of higher dislocations density in the CR materials.

Effect of Cryorolling Strain on Precipitation Kinetics of Al 7075 Alloy

Abstract: The effect of rolling strain on precipitation kinetics of Al 7075 alloy processed at liquid nitrogen temperature has been investigated in the present work. The Al 7075 alloy plates were solutionized and cryorolled with thickness reduction of 35% and 90%. The microstructural characterizations of the bulk and cryorolled Al alloy samples were carried out by electron backscatter diffraction analysis (EBSD) and transmission electron microscopy (TEM), respectively. The cryorolled Al alloys upon 90% thickness reduction exhibit ultrafine grained microstructure. The DSC results of cryorolled Al 7075 alloys obtained at different heating rates are used to calculate activation energies for the evolution of precipitates. The influence of different reduction rates on activation energy of precipitate formation in the cryorolled Al 7075 alloys was analyzed. The present study has shown that an ultrafine-grained Al 7075 alloy exhibits a higher driving force for the precipitation formation when compared to that of its bulk Al alloys.

A comparative study on mechanical properties of ultrafine-grained Al 6061 and Al 6063 alloys processed by cryorolling

Abstract: The present work has been focused to investigate the mechanical behavior and microstructural characteristics of cryorolled Al 6063 and Al 6061 alloys. Hardness and tensile tests of the cryorolled Al alloys were carried out to understand its deformation behavior. SEM/EBSD was used to characterise the microstructures of cryorolled Al alloys and observed the formation of ultrafine-grained microstructures in the materials due to severe plastic strain induced during cryorolling. XRD was used to analyse the formation of different phases during cryorolling of the Al alloys. It is evident from the present study that UFG Al alloys exhibit higher hardness and strength when compared to the bulk Al alloys due to the grain size, higher dislocation density and precipitation hardening effect. The cryorolled Al 6061 alloys exhibit higher tensile strength (346 MPa) and hardness (120 Hv) as compared to Al 6063 alloys (Tensile strength: 240MPa and Hardness: 96.5 Hv) in the present investigation. The deformation mechanisms of UFG Al alloys contributing to their enhanced strength are discussed.