Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 17: Poster Session
MM 17.58: Poster
Montag, 26. März 2012, 17:00–19:00, Poster B
An approach for quantitative assessment of shear induced mixing in mechanical alloying — •Mohsen Pouryazdan1, Di Wang1, Torsten Scherer1, Robert Averback2, and Horst Hahn1 — 1Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology, D-76021, Karlsruhe, Germany — 2Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green St., Urbana, IL 61801, USA
A critical feature in the processing of nanocomposites is the forced mixing of alloying components. By forced mixing we refer to the atomic mixing of atoms attributed to shear deformation. Presently, this process is only poorly understood. This lack of understanding is partly because nearly all of our information to date has been derived from experiments employing ball milling (BM), for which the mixing conditions: strain rate, total strain, temperature, and stress state are poorly characterized. In contrast to experiments using BM, our experimental approach using high pressure torsion (HPT) allows quantitative assessment of mixing conditions. In the current study, Ag60Cu40 two-phase immiscible alloy was processed by HPT for various levels of strain. The state of intermixing was investigated by XRD, DSC and TEM.
It is observed that the rate of chemical disordering increases with the accumulation of applied strain. A complete chemical homogenization of the original lamellar structure of Ag60Cu40, with periodicity of ~165 nm, is achieved after a shear strain of ~725 at a shear strain rate of ~1.5 1/s. The chemical mixing is accompanied by extensive grain refinement leading to nanocrystalline grains with average size of ~42 nm.