Effect of electropulsing treatment on static recrystallization behavior of cold-rolled magnesium alloy ZK60 with different reductions

doi:10.1016/j.jmst.2018.11.008

Abstract

Abstract:

Effect of electropulsing treatment (EPT) on recrystallization behavior of cold-rolled Mg alloy ZK60 strips was investigated. It was found that EPT significantly improved nucleation rate and migration ability of grain boundaries, leading to accelerated recrystallization of the deformed metals at relatively low temperature. After the recrystallization induced by EPT, the average grain size of 20% rolling reduction samples decreased from 113 μm to around 10 μm, meanwhile the typical basal-type texture of the cold-rolled sample was weakened. EPT was normally accompanied with a thermal and an athermal effects. The athermal effect played a dominated role in increasing nucleation rate, while the thermal effect promoted grain growth. A fewer recrystallized grains originated along the grain boundaries in the 10% reduction samples, while most of the recrystallization took place inside the twins in the 20% reduction samples.

Key words: Mg alloys, Recrystallization, Athermal effect, Twins

Huijun Guo, Xun Zeng, Jianfeng Fan, Hua Zhang, Qiang Zhang, Weiguo Li, Hongbiao Dong, Bingshe Xu. Effect of electropulsing treatment on static recrystallization behavior of cold-rolled magnesium alloy ZK60 with different reductions[J]. J. Mater. Sci. Technol., 2019, 35(6): 1113-1120.

Figures/Tables 12

Fig. 1. (a) Schematic view of EPT process and (b) typical electropulsing wave of EPT (I: electropulsing current).

Table 1 Experimental conditions of ZK60 strip under EPT.

Sample No.	Rolling reduction (%)	Duration (μs)	Processing time (s)
1 2 3 4 5 6 7 8 9 10 11 12 13	10 10 15 15 15 15 15 15 15 15 20 20 20	30 30 20 20 25 25 25 30 30 30 30 30 30	600 3600 600 3600 600 1800 3600 600 1800 3600 600 1800 3600

Fig. 2. Optical micrographs of ZK60 alloy: (a) as received; (b) solution treated; (c) 10% reduction; (d) 15% reduction; (e, f) 20% reduction.

Fig. 3. Optical micrographs of 10% reduction samples treated by EPT with duration of 30 μs: (a) sample 1; (b) sample 2.

Fig. 4. Optical micrographs of 15% reduction samples with different EPT parameters: (a) sample 3; (b) sample 4; (c) sample 5; (d) sample 6; (e) sample 7; (f) sample 8; (g) sample 9; (h) sample 10.

Fig. 5. Optical micrographs of 20% reduction samples with different EPT parameters: (a) sample 11; (b) sample 12; (c) sample 13.

Fig. 6. EBSD orientation mapping of samples under 30 μs duration: (a) sample 8; (b) sample 10; (c) sample 13.

Fig. 7. {0002} pole figures of samples under 30 μs duration: (a) sample 8; (b) sample 10; (c) sample 13.

Fig. 8. Misorientation angle distributions of (a) sample 8, (b) sample 10 and (c) sample 13.

Fig. 9. Tensile stress-strain curve of ZK60 samples at RT.

Table 2 Measured temperature of different conditions.

Rolling reduction (%)	Duration τ_p (μs)	Measured temperature (K)
10	30	448.8
15	30	434.4
20	30	414.3
15	20	340.7
15	25	377.1

Fig. 10. Microstructure of 20% reduction sample processed by traditional heat treatment.

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