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On the Influence of the Misorientation of Grains, Grain Size and Boundary Volume on the Strength and Ductility of Ultrafine Grained Cu

Published online by Cambridge University Press:  15 March 2011

Florian H. Dalla Torre ,
Rimma Lapovok ,
Peter F. Thomson ,
James D. Sandlin ,
Chris H.J. Davies  and
Elena V. Pereloma
Florian H. Dalla Torre
Affiliation:
School of Physics and Materials Engineering, Monash University, VIC, 3800, Australia
Rimma Lapovok
Affiliation:
School of Physics and Materials Engineering, Monash University, VIC, 3800, Australia
Peter F. Thomson
Affiliation:
School of Physics and Materials Engineering, Monash University, VIC, 3800, Australia
James D. Sandlin
Affiliation:
School of Physics and Materials Engineering, Monash University, VIC, 3800, Australia
Chris H.J. Davies
Affiliation:
School of Physics and Materials Engineering, Monash University, VIC, 3800, Australia
Elena V. Pereloma
Affiliation:
School of Physics and Materials Engineering, Monash University, VIC, 3800, Australia
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Abstract

The influence of the microstructure and the misorientation relationship of grains on mechanical properties is investigated in specimens of ultrafine-grained copper processed by equal channel angular extrusion (ECAE) route Bc for 1, 4 and 12 passes. XRD texture analyses have shown that the major texture component is developed during the first pass of ECAE, and remains approximately constant with greater number of passes. EBSD measurements indicate that the majority of grain boundaries are still of low angle (>15°), while after four and twelve passes more than 50 % of all boundaries are high angle ones. TEM analyses have shown that the microstructure evolves from microbands and elongated cells towards a more equiaxed homogenous microstructure. On the microscale observed by TEM the degree of misorientation among subgrains/cells increases and the width of boundaries decreases while the cell/subgrain size remains approximately constant as the number of passes increases. The mechanical properties show a saturation level with a maximum in the yield stress and UTS after 4 passes. The strength of the material decreases between the fourth and the twelfth passes and the uniform elongation increases. It is suggested that the increase in ductility (and decrease in strength) is associated with the decrease in width of boundaries leading to an increase in the mean free path of dislocations.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 821: Symposium P – Nanoscale Materials & Modeling-Relations Among Processing, Microstructure and Mechanical Properties , 2004 , P9.10
Copyright
Copyright © Materials Research Society 2004

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