時效制度對Al–Zn?Mg合金組織和抗應力腐蝕性能的影響

葉凌英; 楊汶卿; 唐建國; 劉勝膽; 鄧運來; 張新明

doi:10.13374/j.issn2095-9389.2018.12.28.005

時效制度對Al–Zn?Mg合金組織和抗應力腐蝕性能的影響

doi: 10.13374/j.issn2095-9389.2018.12.28.005

葉凌英^{1, 2, 3},
楊汶卿^{1, 2, 3},
唐建國^{1, 2, 3, ,},
劉勝膽^{1, 2, 3},
鄧運來^{1, 2, 3},
張新明^{1, 2, 3}

1.
中南大學材料科學與工程學院，長沙 410083
2.
中南大學有色金屬材料科學與工程教育部重點實驗室，長沙 410083
3.
中南大學有色金屬先進結構材料與制造協同創新中心，長沙 410083

基金項目: 國家重點基礎研究發展規劃資助項目（2016YFB0300901）

詳細信息

通訊作者:
E-mail：jgtang@csu.edu.cn

中圖分類號: TG146.2
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出版歷程
- 收稿日期: 2018-12-27
- 刊出日期: 2019-12-01

Effect of aging on the microstructure and stress corrosion resistance of Al–Zn?Mg alloy

YE Ling-ying^{1, 2, 3},
YANG Wen-qing^{1, 2, 3},
TANG Jian-guo^{1, 2, 3
, ,},
LIU Sheng-dan^{1, 2, 3},
DENG Yun-lai^{1, 2, 3},
ZHANG Xin-ming^{1, 2, 3}

1.
School of Materials Science and Engineering, Central South University, Changsha 410083, China
2.
Key Laboratory of Nonferrous Metal Materials Science and Engineering (Ministry of Education), Central South University, Changsha 410083, China
3.
Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Center, Central South University, Changsha 410083, China

More Information

Corresponding author: E-mail: jgtang@csu.edu.cn

摘要

摘要: 采用慢應變速率拉伸應力腐蝕、室溫拉伸、透射電鏡等檢測方法，研究傳統T5、T73時效處理，以及新型T5I4、T5I6斷續時效處理對Al–Zn?Mg合金微觀組織、室溫拉伸性能及抗應力腐蝕性能的影響。結果表明：斷續時效T5I4處理后材料抗拉強度為400.0 MPa，明顯高于傳統T5及T73態樣品，但材料抗應力腐蝕性能變差，應力腐蝕敏感系數為5.7%；而經斷續時效T5I6處理后，材料的抗拉強度為408.5 MPa，較T5I4態相比有所提升，與此同時抗應力腐蝕性能也得到明顯改善，應力腐蝕敏感系數為3.2%，該值明顯小于T5I4及T5態；T5I4態晶內析出相平均粒徑為2.0 nm，體積分數為8.8%，均明顯小于其他3種時效制度，其晶界析出相為細小且連續分布的點狀析出相；而經T5I6時效處理后晶內析出相體積分數為24.6%，明顯大于其他3種時效制度，晶內析出相平均粒徑（4.1 nm）較T5I4態有所增大，但依然小于T5、T73態，其晶界處析出相與T5I4態相比更加粗大，呈斷續分布形貌。
- Al–Zn?Mg合金 /
- 斷續時效 /
- 抗應力腐蝕 /
- 微觀組織 /
- 室溫拉伸
Abstract: Controlling the balance between mechanical properties and stress corrosion resistance of Al–Zn?Mg alloys by aging tempers has long been an active focal point of research. Traditional peak-age can improve the mechanical properties, but the continuous precipitate at the grain boundary reduces the stress corrosion resistance of the alloy. While alloys in over-aged (T73) condition show good resistance to stress corrosion, their mechanical properties will drop significantly. In this paper, tensile properties, resistances to stress corrosion, and microstructures of the Al–Zn?Mg alloy, in interrupted aged (T5I4, T5I6) and traditional (T5, T73) tempers, were studied using a tensile test, a slow strain rate tensile test, and transmission electron microscopy. Results reveal that the tensile strength of T5I4 temper is 400.0 MPa, higher than that of T5,T73 tempers, while the stress corrosion resistance is clearly compromised, with index of slow strain rate testing, I_SSRT, of 5.7%, significantly larger than that of the other three aging treatments. The tensile strength of the T5I6 temper increases to 408.5 MPa, and the stress corrosion resistance is also improved, to I_SSRT=3.2%, significantly lower than that of T5 and T5I4 tempers. Volume fraction (8.8%) and average particle diameter (2.0 nm) of intragranular precipitates of T5I4 temper has the minimum value among the four aging treatments, and there are large numbers of fine precipitates distributed continuously at grain boundaries. In the T5I6 temper, the number of intragranular precipitates increase significantly, and the volume fraction of intragranular precipitates is 24.6%, larger than that of the other three aging treatments. In addition, the average particle diameter (4.1 nm) of the intragranular precipitates of the T5I6 temper is larger than that of the T5I4 temper, but is still smaller than that of the T5 and T73 tempers. Precipitates at the grain boundaries of the T5I6 temper are unevenly distributed, and significantly larger than those of the T5I4 temper.
- Al–Zn?Mg alloy /
- interrupted aging /
- stress corrosion resistance /
- microstructure /
- tensile property

HTML全文

圖 1 不同時效態合金晶內析出相透射電鏡圖片及選區電子衍射花樣。（a）T5態；（b）T73態；（c）T5I4態；（d）T5I6態

Figure 1. TEM micrographs and corresponding SAED patterns of intragranular precipitates of the alloy in different ageing conditions:（a）T5；（b）T73；（c）T5I4；（d）T5I6

下載: 全尺寸圖片幻燈片

圖 2 不同時效制度下7020鋁合金晶內析出相粒徑分布圖.(a) T5態；(b) T73態；(c) T5I4態；(d) T5I6態

Figure 2. Diameter distribution of intragranular precipitates of 7020 aluminum alloy under different aging treatments:(a) T5；(b) T73；(c) T5I4；(d) T5I6

下載: 全尺寸圖片幻燈片

圖 3 不同時效制度下7020鋁合金晶界處TEM圖。(a) T5態；(b) T73態；(c) T5I4態；(d) T5I6態

Figure 3. TEM images of grain boundaries of 7020 aluminum alloy under different ageing treatments：(a) T5；(b) T73；(c) T5I4；(d) T5I6

下載: 全尺寸圖片幻燈片

表 1 實驗所用7020鋁合金化學成分（質量分數）

Table 1. Chemical composition of the investigated 7020 aluminum alloy %

Zn	Mg	Mn	Cr	Zr	Cu	Fe	Si	Ti	Al
4.42	1.19	0.29	0.19	0.13	0.12	0.11	0.07	0.05	余量

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表 2 實驗采用時效制度具體參數

Table 2. Specific parameters of aging treatment process of samples

時效制度	具體時效溫度及時長
T5	120 ℃/96 h
T73	90 ℃/12 h+169 ℃/12 h
T5I4	130 ℃/2 h+65 ℃/168 h
T5I6	130 ℃/2 h+65 ℃/168 h+130 ℃/42 h

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表 3 不同時效狀態下合金的室溫拉伸性能

Table 3. Tensile properties of different aged samples

時效狀態	R_m/MPa	R_p0.2/MPa	屈強比/%	延伸率/%
T5	391.6±2.0	343.5±0.5	87.7	12.2±0.5
T73	354.1±4.3	297.1±0.7	83.9	12.7±0.1
T5I4	400.0±3.7	272.1±3.1	68.0	17.1±0.8
T5I6	408.5±1.9	361.4±3.1	88.5	13.0±0.9

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表 4 不同時效狀態下合金慢應變速率拉伸應力腐蝕性能

Table 4. Slow strain rate tensile properties of different aged samples

時效狀態	拉伸介質	斷裂時長/h	抗拉強度/MPa	延伸率/%
T5	硅油	38.3±3.8	370.5±5.4	16.8±0.7
T5	3.5% NaCl	35.1±2.4	363.9±4.1	14.8±0.4
T73	硅油	41.5±2.4	330.3±4.7	15.3±0.5
T73	3.5% NaCl	40.5±0.3	322.9±5.9	14.6±0.2
T5I4	硅油	71.3±3.5	417.2±7.6	23.0±1.9
T5I4	3.5% NaCl	67.5±2.8	401.0±8.6	20.7±0.2
T5I6	硅油	47.7±0.2	401.2±8.4	14.7±0.4
T5I6	3.5% NaCl	43.5±0.9	390.8±7.5	14.0±0.5

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表 5 不同時效態合金應力腐蝕敏感系數表

Table 5. Stress corrosion index of different aged samples

時效狀態	I_SSRT/%
T5	3.5±0.3
T73	2.8±0.5
T5I4	5.7±0.6
T5I6	3.2±0.2

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表 6 不同時效狀態下合金晶內析出相平均粒徑及體積分數

Table 6. Average particle diameters and volume fractions of intragranular precipitates of the alloy in different ageing conditions

時效狀態	晶內析出相平均粒徑/nm	體積分數/%
T5	5.6±0.2	21.9±1.4
T73	6.2±0.4	19.9±0.9
T5I4	2.0±0.1	8.8±1.1
T5I6	4.1±0.4	24.6±2.1

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