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Solid‐State Foaming by Oxide Reduction and Expansion: Tailoring the Foamed Metal Microstructure in the Cu–CuO System with Oxide Content and Annealing Conditions
Author(s) -
Atwater Mark A.,
Darling Kris A.,
Tschopp Mark A.
Publication year - 2016
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201500063
Subject(s) - materials science , annealing (glass) , oxide , microstructure , porosity , grain size , metal , chemical engineering , composite material , metallurgy , engineering
A new method of introducing porosity into solid metals was investigated using mixtures of Cu and CuO. The process involves distributing oxides through the Cu matrix (e.g., mechanical milling, as used here) and then reducing those oxides during annealing. The most distinguishing characteristic of this process is that pores develop within individual powder particles. In this study, we varied the oxide content (0–7 at% O), annealing temperature (400, 600, and 800 °C), and annealing time (up to 3 h) to investigate their effect on the foamed metal microstructure. In general, we find that the amount of porosity within the powder particles (or bulk part) can be controlled by varying of oxide content and annealing parameters. The maximum porosity of 47.4% corresponds to intermediate conditions of both temperature and oxide content (600 °C and ≈3 at% CuO, respectively). The pore size and grain size are small (<5 μm) in comparison with other solid‐state foaming techniques and are not highly sensitive to the annealing parameters used in the present study. The unique mechanisms and opportunities associated with this oxide reduction and expansion process are discussed for the Cu–CuO system as well as extensions to other metal systems.