Influence of equal-channel angular extrusion on impact toughness of aluminum and brass at room and low temperatures

Jyhwen Wang,Angie Hill Price,K Vadiraja Sudhakar,Huanlin Zhu

doi:10.1186/s40712-014-0019-2

Abstract

Abstract Background Equal-channel angular extrusion is a severe plastic deformation process that can be used for grain refinement to improve material properties of bulk metals. In this paper, the effect of equal-channel angular extrusion on the impact toughness of aluminum 1100 and brass C26000 was investigated. Methods Brass and aluminum materials were extruded in two and four passes using two equal-channel angular extrusion processing routes. Specimens were tested for hardness and Charpy impact toughness. Microstructure and fractography were examined. Results The results showed the hardness remained almost constant after two passes for both brass and aluminum. Impact energy of brass after two passes decreased due to increase in dislocation density whereas for aluminum it remained almost constant after four passes due to the formation of ultrafine grains in addition to deformation/dislocation structures. Impact energies of specimens tested at room temperature and low temperature (−70°C) were almost the same due to their face-centered crystal structure. It was also found that the impact toughness of a specimen with a non-distorted notch surface is higher than that of a specimen with a distorted notch surface. Conclusions It is evident from the present study that the number of passes determines the extent of ultrafine grain structure that is known to increase impact toughness of equal-channel angular extrusion processed materials. All of these observed characteristics can influence material and process selections in practical design applications.

Highlights

Equal-channel angular extrusion is a severe plastic deformation process that can be used for grain refinement to improve material properties of bulk metals
Equal-channel angular extrusion (ECAE), twist extrusion, high pressure torsion, and friction stir processing are all severe plastic deformation (SPD) processes that can result in ultrafine grain (UFG) microstructures in metals
The middle sections were used for hardness measurement and microstructure evaluation of the materials before and after ECAE

Summary

Introduction

Equal-channel angular extrusion is a severe plastic deformation process that can be used for grain refinement to improve material properties of bulk metals. Equal-channel angular extrusion (ECAE), twist extrusion, high pressure torsion, and friction stir processing are all severe plastic deformation (SPD) processes that can result in ultrafine grain (UFG) microstructures in metals. As UFG materials are known to exhibit enhanced mechanical properties, SPD processes have been extensively studied (Valiev and Langdon 2006). In ECAE, the workpiece/billet is pressed through a die with intersecting channels having the same cross section. As the billet can be extruded repeatedly in successive passes, ECAE has the advantage of producing large cumulative strain without changing the cross section of the workpiece (Rebhi et al 2009). The workpiece possesses fine grains with enhanced properties that can have various design applications

Methods

Results

Conclusion