The wear mechanism in disk-on-disk tests of a Cu–Be alloy against AISI D2 steel counterparts changes from metallic to oxidative for increasing loads. At low load the wear debris are made of the Cu–Be alloy, whereas above 50 N the main constituents are copper oxides, with a few residual particles of the copper-base alloy. Despite the lower oxidation state, cuprite (Cu2O) is the main fraction of the high- load debris, whereas tenorite (CuO) is less than 10%. An analysis of the X-ray diffraction line profile, supported by high-resolution trans- mission electron microscopy (TEM), shows that cuprite domains are nanocrystalline, with domain sizes distributed about a mean value of 12 ‚ 13 nm, and contain a high density of dislocations (5 · 1016 m2). The small domain size is considered as a possible stabilization mechanism of cuprite against the higher oxidation state oxide tenorite, whereas the large dislocation content is a consequence of the heavy plastic deformation in the contact area. As a further support to the size-stabilization mechanism, a diffraction measurement repeated on the wear debris after a 6 month aging shows a marked increase in the tenorite fraction. According to line profile analysis, the remaining cuprite fraction is made up of nanocrystalline domains (6 nm) smaller than in the as-produced debris, thus supporting the hypothesis that small cuprite grains are more stable than larger ones, which more easily transform to tenorite.

Microstructure of Cu-Be alloy triboxidative wear debris / Scardi, Paolo; Leoni, Matteo; Straffelini, Giovanni; G. B., De Giudici. - In: ACTA MATERIALIA. - ISSN 1359-6454. - STAMPA. - 55:7(2007), pp. 2531-2538. [10.1016/j.actamat.2006.11.046]

Microstructure of Cu-Be alloy triboxidative wear debris

Scardi, Paolo;Leoni, Matteo;Straffelini, Giovanni;
2007

Abstract

The wear mechanism in disk-on-disk tests of a Cu–Be alloy against AISI D2 steel counterparts changes from metallic to oxidative for increasing loads. At low load the wear debris are made of the Cu–Be alloy, whereas above 50 N the main constituents are copper oxides, with a few residual particles of the copper-base alloy. Despite the lower oxidation state, cuprite (Cu2O) is the main fraction of the high- load debris, whereas tenorite (CuO) is less than 10%. An analysis of the X-ray diffraction line profile, supported by high-resolution trans- mission electron microscopy (TEM), shows that cuprite domains are nanocrystalline, with domain sizes distributed about a mean value of 12 ‚ 13 nm, and contain a high density of dislocations (5 · 1016 m2). The small domain size is considered as a possible stabilization mechanism of cuprite against the higher oxidation state oxide tenorite, whereas the large dislocation content is a consequence of the heavy plastic deformation in the contact area. As a further support to the size-stabilization mechanism, a diffraction measurement repeated on the wear debris after a 6 month aging shows a marked increase in the tenorite fraction. According to line profile analysis, the remaining cuprite fraction is made up of nanocrystalline domains (6 nm) smaller than in the as-produced debris, thus supporting the hypothesis that small cuprite grains are more stable than larger ones, which more easily transform to tenorite.
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Scardi, Paolo; Leoni, Matteo; Straffelini, Giovanni; G. B., De Giudici
Microstructure of Cu-Be alloy triboxidative wear debris / Scardi, Paolo; Leoni, Matteo; Straffelini, Giovanni; G. B., De Giudici. - In: ACTA MATERIALIA. - ISSN 1359-6454. - STAMPA. - 55:7(2007), pp. 2531-2538. [10.1016/j.actamat.2006.11.046]
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