| Compared to coarse grained materials,ultra-fine graine materials have many excellent mechanical properties,but its corrosion resistance needs further discussion and research.In this essay,the samples of ultra-fine grain Cu-Cr-Zr alloy was made by equal channel angular pressing（ECAP）.Microstructure of alloys was observed by metallographic microscope and basic physical properties was measured in the meanwhile.By electrochemical experiment,corrosion behavior of ultra-fine grain Cu-Cr-Zr alloy was studied under various conditions respectively,such as different grain degrees,the way of heat treatment,concentration of Cl-,addition of S2-,temperature conditions and acid base chemistry.Corrosion mechanism under all conditions is analyzed and summarized,and the main findings are as follows:（1）After ECAP,the grain size of samples will constantly decreases with the increase of extrusion times.The grain size of coarse alloy is about 50μm and the grain size of ECAP 8 pass deformed alloy is about 150 nm.（2）The corrosion behavior of ultra-fine grain Cu-Cr-Zr alloy was investigated in 0.5M NaCl solution with different ECAP passes by electrochemical experiments.The results show that the corrosion current density decreases with the increasement of ECAP pass and the decreasement of grain size.The corrosion resistance of alloy will be better as the grain size decreases.The corrosion current density of coarse alloy is 2.26 μA·cm-2.The corrosion current density of 8 passes ECAP deformed alloy is 0.54μA·cm-2 and it reduces the one order of magnitude.After fitting the equivalent circuit,the transfer resistance of diffusion process increases with the pass increasing.It increases to ECAP 8 passes’ 14130Ω from coarse specimen’s 97.46Ω.It indicates that charge transfer between corrosive medium and electrode becomes difficult and the corrosion resistance of alloy improves.（3）The corrosion behavior of Cu-Cr-Zr alloy was investigated in 0.5mol/L NaCl solution with different heat treatment by electrochemical experiments.We can find that in the coarse grain state,the samples in the state of aging treatment have better corrosion resistance and the corrosion current density of aging samples decrease to 2.01μA·cm-2 from 2.26μA·cm-2 of not aging samples.While the ECAP 8 passes deformed samples without aging have better corrosion resistance and the corrosion current density of samples without aging decrease to 0.54μA·cm-2 from 3.97 μA·cm-2 of aging samples.（4）The corrosion behavior of Cu-Cr-Zr alloy was investigated under different concentration of Cl-.The results show that corrosion current density of the specimen increase and the corrosion resistance declines with the increase of concentration of Cl-.Meanwhile the effect of Cl-concentration on corrosion resistance is not obvious in high values.The corrosion behavior of Cu-Cr-Zr alloy was investigated in 0.5 mol/L NaCl solution with the addition of S2-.The results show that ultra-fine specimens have denser products layer and slower corrosion speed compared to coarse specimens and show better corrosion resistance.At the same condition,they show better corrosion resistance than when they do not contain S2-.The corrosion behavior of ultra-fine grain Cu-Cr-Zr alloy was investigated in different temperature of solution.We find that corrosion resistance declines with the temperature increases.（5）The corrosion behavior of Cu-Cr-Zr alloy was investigated under acid base chemistry.We find that,in HCl solution,the corrosion current density of specimens increases with the increasement of solution concentration and corrosion resistance of material becomes worse.It’s opposite in NaOH solution,the corrosion current density of specimens decreases with the increasement of solution concentration and corrosion resistance of material becomes better.And in same solution,the corrosion current density of UFG specimens is smaller than coarse specimens’ and show better corrosion resistance. |
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