Abstract
The microstructure evolution and stress corrosion cracking (SCC) behaviors of ultrafine-grained (UFG) Cu-Cr-Zr alloys processed by equal-channel angular pressing (ECAP) and coarse-grain (CG) Cu-Cr-Zr alloys within NaNO2 solution were systematically investigated in the current study. After deformation by eight ECAP passes, the grain size was refined to ~200 nm. The slow strain rate tensile (SSRT) tests showed that the ultimate tensile strength (UTS) of CG samples in solution was slightly lower than that in the air, and the elongation was decreased from 57.3% to 52.6%. In contrast, both the UTS and elongation of UFG samples in air and solution were almost identical. In NaNO2 solution, the CG fracture surface showed an obvious dissolution, microvoids, and minor cracks, while the surface of the UFG fracture was relatively smooth. The resistance of UFG samples to SCC could be significantly enhanced compared with CG samples. The grain boundary volume fraction of UFG alloy was dramatically increased, which reduced the formation of pitting corrosion. In addition, the uniform distribution of Cr particles also improved the corrosion resistance of UFG alloys.
Highlights
Cu-Cr-Zr alloy is a typical precipitation-strengthened alloy with excellent mechanical properties, and is widely used in industrial fields involving high mechanical strength and high electrical conductivity, such as integrated circuit lead frames, continuous casting machine crystallizer lining, and the preparation of electric resistance welding electrodes [1,2,3]
Cu alloys are susceptible to stress corrosion cracking (SCC)
The sensitivity of CG and UFG Cu-Cr-Zr alloys to SCC in air and 1 M NaNO2 solution was
Summary
Cu-Cr-Zr alloy is a typical precipitation-strengthened alloy with excellent mechanical properties, and is widely used in industrial fields involving high mechanical strength and high electrical conductivity, such as integrated circuit lead frames, continuous casting machine crystallizer lining, and the preparation of electric resistance welding electrodes [1,2,3]. Severe plastic deformation (SPD) is an effective method for improving the mechanical properties of materials and refining grains. ECAP (equal-channel angular pressing) is one of the most widely used technologies in SPD, and can produce an ultrafine-grained (UFG) structure in Cu-Cr-Zr alloy with superior mechanical properties [4,5]. The serious corrosion failure problems of Cu alloys greatly limit their engineering applications [6,7]. Cu alloys are susceptible to stress corrosion cracking (SCC). When subjected to the synergy of mechanical stress and corrosion medium. Recent studies have insufficiently focused on the SCC behaviors of UFG Cu alloys [8,9,10]
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