Influence of Zn Content on Microstructures, Mechanical Properties and Stress Corrosion Behavior of AA5083 Aluminum Alloy

doi:10.1007/s40195-020-01063-7

Abstract

Abstract:

To enhance the stress corrosion cracking (SCC) resistance, Zn was utilized as an alloy element to add in the AA5083 aluminum alloys. The effects of Zn content on the microstructures, mechanical properties and SCC resistance were systematically evaluated. The results demonstrate that in the studied range adding Zn can significantly improve the SCC resistance of the AA5083 alloys. This is related to the relatively low amount of continuous β (Al₃Mg₂) phase along grain boundary and the formation of Zn-containing phase such as Al₅Mg₁₁Zn₄ phase. Based on the results, the optimal Zn content with respect to SCC resistance is approximately 0.50 wt.%. Further increasing Zn content results in coarse precipitates discontinuously distributed along grain boundaries.

Key words: AA5083 aluminum alloy, Slow strain rate test, Precipitation, Stress corrosion cracking

Zhixiong Zhu, Xingxu Jiang, Gang Wei, Xiaogang Fang, Zhihong Zhong, Kuijing Song, Jian Han, Zhengyi Jiang. Influence of Zn Content on Microstructures, Mechanical Properties and Stress Corrosion Behavior of AA5083 Aluminum Alloy[J]. Acta Metallurgica Sinica (English Letters), 2020, 33(10): 1369-1378.

Figures/Tables 12

Table 1 Chemical composition of the studied AA5083 alloys with various Zn contents (wt.%)

Alloy No.	Zn	Mg	Mn	Cr	Si	Fe	Al
1	0.00	4.47	0.70	0.152	< 0.02	< 0.02	Bal.
2	0.25	4.50	0.70	0.152	< 0.02	< 0.02	Bal.
3	0.50	4.48	0.71	0.146	< 0.02	< 0.02	Bal.
4	0.75	4.49	0.68	0.151	< 0.02	< 0.02	Bal.

Fig. 1 Typical microstructure of the AA5083 alloy (0.25% Zn content): a three-dimensional micrograph, b band contrast map imposed on grain boundary map

Fig. 2 SEM micrographs and the corresponding EDS analyses of the AA5083 alloys with various Zn contents: a 0%, b 0.25%, c 0.50%, d 0.75% (in wt.%)

Fig. 3 TEM characterization of typical precipitates in the AA5083 alloys with various Zn contents: a-c 0%, d-g 0.25%, h-j 0.50%, k-m 0.75% (in wt.%)

Table 2 Mechanical properties and tensile properties of the AA5083 alloys with various Zn contents

Zn (wt.%)	Hardness (HV0.1)	Yield strength (MPa)	Tensile strength (MPa)	Elongation (%)
0	88	168	295	23
0.25	88	155	277	25
0.50	84	162	295	23
0.75	87	160	285	18

Fig. 4 SEM images of the fractured surfaces after tensile tests of the AA5083 alloys with various Zn contents: a 0%, b 0.25%, c 0.50%, d 0.75% (in wt.%)

Fig. 5 SSRT load-displacement curves of the studied AA5083 alloys tested in different conditions: a in air, b in 3.5 wt.% NaCl solution

Table 3 UTS, elongation and breaking time of the AA5083 alloys with various Zn contents obtained from SSRT

Zn (wt.%)	Strength (MPa)		Elongation (%)		Breaking time (h)
Zn (wt.%)	In air	In 3.5% NaCl	In air	In 3.5% NaCl	In air	In 3.5% NaCl
0	310	301	35	15	147	81
0.25	307	298	39	19	161	96
0.50	330	323	44	34	156	130
0.75	328	297	47	18	172	88

Fig. 6 Fractured surfaces (SSRT in 3.5 wt.% NaCl aqueous solution) of the AA5083 alloys with various Zn contents: a 0%, b 0.25%, c 0.50%, d 0.75% (in wt.%)

Table 4 Surface potential of the AA5083 alloys with various Zn contents

Zn (wt.%)	Potential (V)
0	0.94
0.25	1.22
0.50	1.26
0.75	1.13

Fig. 7 Conductivity as a function of Zn content in the AA5083 alloys

Table 5 Elongation loss Iδ, the strength loss σδ, the ratio of breaking time t and SCC index ISSRT of the AA5083 alloys with various Zn contents

Zn (wt.%)	I_δ	σ_δ	t	I_SSRT
0	0.57	0.03	0.55	0.17
0.25	0.51	0.03	0.60	0.17
0.50	0.23	0.02	0.83	0.09
0.75	0.62	0.09	0.51	0.27

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