Precipitation Behavior During Thin Slab Thermomechanical Processing and Isothermal Aging of Copper-bearing Niobium-Microalloyed High Strength Structural Steels: The Effect on Mechanical Properties


We describe here the precipitation behavior of copper and fine-scale carbides during thermo-mechanical processing and isothermal aging of copper-bearing niobium-microalloyed high strength steels. During thermo-mechanical processing, precipitation of ɛ-copper occurs in polygonal ferrite and at the austenite–ferrite interface. In contrast, during isothermal aging, nucleation of ɛ-copper precipitation occurs at dislocations. In the three different chemistries investigated, the increase in strength associated with copper during aging results only in a small decrease in impact toughness, implying that copper precipitates do not seriously impair toughness, and can be considered as a viable strengthening element in microalloyed steels. Precipitation of fine-scale niobium carbides occurs extensively at dislocations and within ferrite matrix together with vanadium carbides. In the presence of titanium, titanium carbides act as a nucleus for niobium carbide formation. Irrespective of the nature of carbides, copper precipitates and carbides are mutually exclusive.


Materials Science and Engineering

Keywords and Phrases

Microalloyed steels; Copper; Mechanical properties

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Document Type

Article - Journal

Document Version


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© 2011 Elsevier, all rights reserved.

Publication Date

01 Jan 2011