Alloy

About: Alloy is a research topic. Over the lifetime, 171884 publications have been published within this topic receiving 1719420 citations. The topic is also known as: alloys.

Effect of Cu Content on Corrosion Behavior of 7xxx Series Aluminum Alloys

Abstract: The corrosion behavior of 7xxx aluminum alloys with various Cu content was investigated using polarization and electrochemical impedance spectroscopy (EIS) techniques. Two breakdown potentials were found in Cu-containing alloys in deaerated chloride solution, and the values increased logarithmically with increasing Cu content. However, in aerated chloride solution, polarization resistance as determined by EIS decreased with increasing Cu content. The first breakdown potential corresponded to transient dissolution associated with attack of the fine hardening particles and the surrounding solid solution in a thin surface layer. The second breakdown potential was associated with combined intergranular and selective grain attack. The correlation between the microstructure, especially Cu content, and corrosion behavior was made by composition analysis of the grain boundary regions including precipitate free zone and grain boundary precipitates as well as the matrix by scanning transmission electron microscopy. The corrosion potential increased with increasing alloy Cu content in aerated chloride solutions because of enhanced rates of oxygen reduction. This degraded the corrosion resistance despite the increase in the breakdown potentials with Cu content.

Microstructural dependence of Fe-high Mn tensile behavior

Abstract: The tensile properties of Fe-high Mn (16 to 36 wt pct Mn) binary alloys were examined in detail at temperatures from 77 to 553 K. The Mn content dependence of the deformation and fracture behavior in this alloy system has been clarified by placing special emphasis on the starting microstructure and its change during deformation. In general, the intrusion of hcp epsilon martensite (e) into austenite (γ) significantly increases the work hardening rate in these alloys by creating strong barriers to further plastic flow. Due to the resulting high work hardening rates, large amounts of e lead to high flow stresses and low ductility. Alloys of 16 to 20 wt pct Mn are of particular interest. While these alloys are thermally stable with respect to bcc α’ martensite formation, 16 to 20 wt pct Mn alloys undergo a deformation induced e →α’ transformation. The martensitic transformation plays two contrasting roles. The stress-induced e→ α’ transformation decreases the initial work hardening rate by reducing locally high internal stress. However, the work hardening rate increases as the accumulated α’ laths become obstacles against succeeding plastic flow. These rather complicated microstructural effects result in a stress-strain curve of anomolous shape. Since both the Ms and Md temperatures for both the e and α’-martensite transformations are strongly dependent on the Mn content, characteristic relationships between the tensile behavior and the Mn content of each alloy are observed.