TY - JOUR

T1 - Flow stress anisotropy and Bauschinger effect in ultrafine grained copper

AU - Haouaoui, M.

AU - Karaman, I.

AU - Maier, H. J.

N1 - Funding Information: This research was supported by National Science Foundation contract no. CMS 01-34554, Solid Mechanics and Materials Engineering Program, Directorate of Engineering, Arlington. HJM acknowledges financial support from Deutsche Forschungsgemeinschaft with the Research Unit program ‘Mechanische Eigenschaften und Grenzflächen ultrafeinkörniger Werkstoffe’.

PY - 2006/12

Y1 - 2006/12

N2 - The effect of strain path and magnitude on the flow stress anisotropy and Bauschinger effect (BE) in ultrafine grained (UFG) copper was investigated. The material billets were deformed via multipass equal channel angular extrusion (ECAE) following several deformation routes. The monotonic stress-strain responses under tension and compression and forward compression/reverse tension response along three perpendicular directions were determined in each billet. It was observed that, in certain cases, the strong tension/compression asymmetry was in favor of tension as opposed to what has so far been reported for UFG materials, and an increase in the number of ECAE passes caused a decrease in yield strength along certain sample directions. Finally, the BE was found to be more pronounced for the lower number of passes. It was shown that crystallographic texture and grain size differences cannot be the only factors responsible for these unexpected observations. Grain morphology and grain boundary character are argued to be additional parameters that have to be taken into account. How these factors affect tension/compression asymmetry, flow anisotropy and BE in UFG copper and how they can help elucidating the observations are discussed.

AB - The effect of strain path and magnitude on the flow stress anisotropy and Bauschinger effect (BE) in ultrafine grained (UFG) copper was investigated. The material billets were deformed via multipass equal channel angular extrusion (ECAE) following several deformation routes. The monotonic stress-strain responses under tension and compression and forward compression/reverse tension response along three perpendicular directions were determined in each billet. It was observed that, in certain cases, the strong tension/compression asymmetry was in favor of tension as opposed to what has so far been reported for UFG materials, and an increase in the number of ECAE passes caused a decrease in yield strength along certain sample directions. Finally, the BE was found to be more pronounced for the lower number of passes. It was shown that crystallographic texture and grain size differences cannot be the only factors responsible for these unexpected observations. Grain morphology and grain boundary character are argued to be additional parameters that have to be taken into account. How these factors affect tension/compression asymmetry, flow anisotropy and BE in UFG copper and how they can help elucidating the observations are discussed.

KW - Anisotropy

KW - Bauschinger effect

KW - Equal channel angular extrusion

KW - Tension-compression asymmetry

KW - Ultrafine grained materials

UR - http://www.scopus.com/inward/record.url?scp=33750627979&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2006.07.022

DO - 10.1016/j.actamat.2006.07.022

M3 - Article

AN - SCOPUS:33750627979

VL - 54

SP - 5477

EP - 5488

JO - Acta materialia

JF - Acta materialia

SN - 1359-6454

IS - 20

ER -