Bauschinger effect on wear of cold-worked Cu and Mg-A study combining molecular dynamics modeling and experimental investigation

Y Tang and A Kumar and DL Chen and DY Li and QY Li and W Li, WEAR, 522, 204726 (2023).

DOI: 10.1016/j.wear.2023.204726

The yield strength of a metal may decrease if it is plastically deformed in an opposite direction prior to the test. This phenomenon is known as the Bauschinger effect, which affects wear of materials under different conditions. For instance, bi-directional sliding could lead to less wear than unidirectional sliding. However, it is unclear how the Bauschinger effect influences wear of strain-hardened metals with different crystal structures which influence the defect generation and annihilation. In this work, we investigated the Bauschinger effect on the wear resis- tance of cold-worked Cu (FCC) and Mg (HCP) combining experiments and molecular dynamics simulations. It was experimentally observed that strain-free Cu had a stronger Bauschinger effect than the cold-worked one, while the situation of undeformed and deformed Mg samples was opposite. The underlying mechanisms were studied via molecular dynamics simulations. It is found that the high-density dislocations in the cold- worked Cu weaken the Bauschinger effect, while the cold-worked Mg with fewer defects has more space for generation and cancellation of defects introduced by wear, leading to a stronger Bauschinger effect. Besides, the Bauschinger effect is also found at the oxide/metal interface, making the oxide scale on worn surfaces less easy to be scratched off during bi-directional sliding, which is beneficial to the wear resistance of metal since the tribo-oxide scale could help withstand the wearing force.

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