Current-driving intergranular corrosion performance regeneration below the precipitates solvus temperature in Al-Mg alloy

doi:10.1016/j.jmst.2020.01.071

Abstract

Abstract:

Heat treatment is an effective method to improve the intergranular corrosion resistance of the sensitized Al-Mg alloy due to dissolution of the grain boundary precipitates above the solvus temperature of β-phase. The grain boundary precipitates will grow and coarsening below the solvus temperature. In this study, the in-situ intergranular corrosion performance regeneration of the sensitized Al-Mg alloy can be realized by low-density electro-pulsing treatment below the solvus temperature of β-phase. Our findings show that the dissolution of grain boundary precipitates by electro-pulsing treatment is accelerated at relatively low temperature in comparison to traditional heat treatment. The athermal effect produced by the interaction between atoms and electrons on the dissolution of grain boundary precipitates is the main reason for the improved corrosion resistance below the solvus temperature of β-phase.

Key words: Aluminium alloys, Phase transformation kinetics, Electro-pulsing treatment, Intergranular corrosion

Di Zhang, Zhen Zhang, Yanlin Pan, Yanbin Jiang, Linzhong Zhuang, Jishan Zhang, Xinfang Zhang. Current-driving intergranular corrosion performance regeneration below the precipitates solvus temperature in Al-Mg alloy[J]. J. Mater. Sci. Technol., 2020, 53: 132-139.

Figures/Tables 11

Table 1 Chemical composition of the experimental alloy (wt.%).

Mg	Mn	Cu	Cr	Ti	Zr	Fe	Si	Al
5.6	0.8	0.15	0.03	0.07	0.15	0.15	0.15	Bal.

Table 2 Experimental parameters of EPT.

	f (Hz)	τ_p (μs)	j (A/mm²)	t (h)	T (K)
EPT1	300	200	5.56	3	383
EPT2	350	200	5.56	3	403
EPT3	380	200	5.56	3	433
EPT4	400	200	5.56	3	453
EPT5	450	200	5.56	3	483
EPT6	450	200	6.30	3	503

Fig. 1. Mass loss (a) and hardness (b) of EPT and heat-treated alloys.

Fig. 2. Distribution of GBPs observed by optical microscope (a) and TEM (b).

Fig. 3. Distribution of GBPs observed by optical microscope: (a) EPT1, (b) EPT2, (c) EPT3, (d) EPT4, (e) EPT5, (f) EPT6.

Fig. 4. Distribution of GBPs observed by TEM: (a) EPT1, (b) EPT2, (c) EPT3, (d) EPT4, (e) EPT5, (f) EPT6.

Fig. 5. Distribution of GBPs observed by optical microscope: (a) RHT1, (b) RHT2, (c) RHT3, (d) RHT4, (e) RHT5.

Fig. 6. Distribution of GBPs observed by TEM: (a) RHT1, (b) RHT2, (c) RHT3, (d) RHT4.

Fig. 7. GBPs observed by TEM (a) and EDS line scan of the GBPs: (b) Line A, (c) Line B.

Fig. 8. Frequency of nearest neighbor distance of GBPs.

Fig. 9. Dissolution of β phase after EPT and heat treatment.

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