TJ436 : Experimental study of severe plastic deformation of zirconium niobium alloy using equal channel angular pressing
Thesis > Central Library of Shahrood University > Mechanical Engineering > MSc > 2016
Authors:
Abstarct: The severe plastic deformation methods have been developed in largely different industries. Use this method high level of strains can be applied to the material. Equal channel angular pressing (ECAP) is one of these methods. In which, the sample can be pressed for many times since the cross section of it does not change. The aim of the process is achieving ultra-fine grained structure and increase the strength and hardness by increasing the density of dislocations. It is the aim of this thesis to study the severe plastic deformation of zirconium niobium alloy using ECAP. Therefore first the ECAP die was disigned and analyzed. Analysis of stresses applied to the die components was performed in two steps using finite element method in Abaqus software. In first step analyzed residual stresses that are caused by press shrink fitting the die in a pressure ring calculated. It was founded that use this pressing created hoop stress of σθ=800MPa in die. In the second step ECAP process is simulated and it is identified the hoop stress of
σθ=280 MPa is induced on the wall of the vertical channel of die. This induced stress is lower than the fracture strength of die. The strain applied at each stage, depends on the angle between the two channels. In die design this angle should have the lowest possible amount so that the greatest amount of strain is applied to sample in each pass and also die does not fail. For this reason, the angle between the two channels was selected to φ=90°. ECAP was carried out at a tempeture of 200°C via route BC in which the sample was rotated 90° in the same sense in each pass. The zirconium niobium alloy was succssesfully ecaped up to 8 passes. Determined micro-hardness and mechanical properties of the sample. The results of fracture shows that dimples size and elongation is reduced. The results of micro hardening and yield stress shows rise 50% after five passes of ECAP.
Keywords:
#Equal channel angular pressing (ECAP) #Ultra-fine grained material #Severe plastic deformation #ECAP die design Link
Keeping place: Central Library of Shahrood University
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Keeping place: Central Library of Shahrood University
Visitor: