Sushanta Kumar Panigrahi

A Comparative study on Mechanical Properties of Al 7075 alloy processed by rolling at cryogenic temperature and room temperature

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 annealing and aging treatment on mechanical properties of ultrafine grained Al 6061 alloy

Abstract A comparative study of aging and a combined treatment of short annealing and aging on mechanical properties and microstructure of cryorolled (CR) Al 6061 alloy is investigated in the present work by using tensile tests, hardness tests, electron backscattered diffraction and transmission electron microscope. The pre-CR solid solution treatment combined with post-CR short annealing (200°C, 5 min) followed by aging treatment (100°C, 57 h) of the Al 6061 alloy showed an improved ductility and well defined ultrafine grain structure as compared to the samples subjected to pre-CR solid solution treatment followed by post-CR aging treatment (100°C, 60 h).

Effect of Cryorolling Strain on Precipitation Kinetics of Al 7075 Alloy

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.

Effect of Ageing on Strength and Ductility of Ultrafine Grained Al 6061 Alloy

An effect of ageing on mechanical properties of ultrafine grained Al 6061 alloys has been investigated in the present work. The solution treated bulk Al 6061 alloy was subjected to cryorolling to produce ultrafine grain structures and subsequently ageing treatment to improve its both strength and ductility. The hardness and tensile properties of solution treated, cryorolled, cryorolled and aged Al alloys were measured and explained by using their corresponding microstructural morphologies. The pre-cryorolled solid solution treatment combined with post-CR ageing treatment (1300C-30h) has been found to be the optimum processing condition to obtain the ultrafine grained microstructure with improved tensile strength (362MPa) and good tensile ductility (10.7%) in the Al 6061 alloy. The combined effect of precipitation hardening and recovery are responsible for the simultaneous improvement of both strength and ductility observed in the present work.

Modeling Structure of Al-Sn Alloy

In metallic alloys, the formation of macrostructure involves different length and time scales. The macrostructure strongly influences the mechanical properties of the materials. Modeling of macrostructure provides valuable insights for tailoring of the macrostructure. In the present study simulation of macrostructure in Al-22Sn has been carried out. Expression for nucleation rate and growth rate were tuned to get a match with the experimentally observed macrostructure. The study incorporates the motion of grains due to Brownian motion. Incorporation of Brownian motion resulted in more uniform distribution locally, which has been experimentally observed. Both simulation and macrograph showed few columnar grains and absence of sharp columnar to equiaxed transition.