MECHANICAL BEHAVIOR OF ULTRAFINE GRAINED ALUMINIUM 2014 ALLOY

Abstract

In recent years, much attention has been paid to develop ultrafine grained materials as the structural materials due to their superior mechanical properties and having a combination of high strength and low weight. An Al-alloy belongs to the same category. To obtain high strength, the most efficient way is to produce fine grain size because the grain size is generally regarded as a principal structural factor affecting the mechanical response of metals and alloys. To obtain the fine grained structure, rolling the material at cryogenic temperature is one of the best options because it produces ultrafine structure. It is known that when a material undergoes severe deformation, the yield strength and fracture strength increases. But this increase in yield strength is followed by the loss of ductility. Aluminium alloys have been used continuously from many years because of their good properties such as low weight, formability, ductility and well established methods to work with them. All these properties favor the demand of current structural applications. Aluminium is being used in automobile and aerospace industry mainly due to its added advantage of low weight, so that the components made from it can reduce the overall weight and hence, the overall reduction of operating cost of the vehicle. In addition to low weight, the demand of high strength should also be met. The present work has been performed to investigate the mechanical properties of ultrafine grained Al 2014 alloy with a thickness reduction of 90% and 70% produced by cryorolling. The properties of UFG are compared with that of the bulk material. To study the effect of cryorolling, the sample cut from the bulk material were given the required solution treatment, subjected to rolling at cryogenic temperature using liquid nitrogen and then tensile & hardness test were performed after getting the desired thickness reduction.. The fatigue behavior of this cryorolled alloy has been determined experimentally. Also a consideration is given to determine its resistance against crack propagation. For this purpose, fracture toughness testing has been done. In order to get an idea about the improvement in properties, the results obtained for this cryorolled alloy have been compared with the results of solution treated alloy. From this experimental study, it is found that the strength and hardness increases but percentage elongation decreases as the thickness of the material is reduced by rolling at liquid nitrogen temperature.