State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
Cite this article:
Hui XING, Mingxing GUO, Xiaofeng WANG, Yan ZHANG, Jishan ZHANG, Linzhong ZHUANG. EFFECT OF Fe-RICH PHASE PARTICLES WITH DIFFER-ENT CONCENTRATIONS ON THE BENDABILITYOF Al-Mg-Si-Cu SERIES ALLOYS. Acta Metall Sin, 2016, 52(3): 271-280.
The influence of Fe-rich phase particle with different contents on the bendability of the Al-Mg-Si-Cu alloys was investigated by means of bending and tensile tests, OM, SEM and TEM characterization. The results reveal that, with the increase of Fe-rich phase particle content, the bendability of the alloy sheets in the longitudinal and transverse directions was quite different, and the outer surface of the alloy sheets after bending of 180° along the two directions became much rough, especially along the transverse direction. When the Fe-rich phase concentration increased to the medium level (0.2%Fe), the quality of outer surface after bending was very good. With further increasing Fe-rich phase to the high level (0.5%Fe), micro cracks were produced after bending along the transverse direction. Although increasing Fe-rich phase concentration did not give a great effect on the elongation of the alloys in the two directions, according to the tensile fracture and microstructure in the slid surface of the specimen after bending or tension test, the roughening of outer surface of the alloy sheet without Fe-rich phase was closely related with the formation of shear bands, while for the alloy sheet with high concentration of Fe-rich phases, the formation of micro cracks after bending was mainly related with the size, morphology and distribution of coarse Fe-rich phases. In addition, based on the quantitative relationship between Fe-rich phase concentration and bendability of the alloy sheets, the models of outer surface roughening and micro cracks forming during bendingare proposed.
Fund: Supported by National High Technology Research and Development Program of China (No.2013-AA032403), National Natural Science Foundation of China (Nos.51571023 and 51301016), Fundamental Research Funds for the Central Universities (NoFRF-TP-15-051A3) and Constructed Project for Key Laboratory of Beijing (No FRF-SD-B-005B)
Table 1 Chemical compositions of experimental Al-Mg-Si-Cu alloys (mass fraction / %)
Fig.1 Schematics of cutting way of bending sample(a) and semi-guided bend test (b) (1--clamp, 2--former, t--thickness of test piece, r--radius of the former)
Fig.2 Low (a~c) and high (d~f) magnified SEM images of alloys No.1 (a, d), No.2 (b, e) and No.3 (c, f) in the solution treatment condition and EDS analysis of particle A in Fig.2e (g) and particle B in Fig.2f (h)
Fig.3 TEM images of alloys No.1 (a) and No.3 (b) in the solution treatment condition and SAED pattern of particle A in Fig.3b (c)
Fig.4 Surface morphologies of the pre-aged alloy sheets after 180° bending treatment (0°--bending along the longitudinal direction, 90°--bending along the transverse direction)
Fig.5 OM images of alloys No.1 (a, b), No.2 (c, d) and No.3 (e, f) after bending along the longitudinal (a, c, e) and transverse (b, d, f) directions
Fig.6 SEM images of alloy No.3 after bending along longitudinal (a) and transverse (b) directions, high magnification of rectangular area in Fig.6b (c) and EDS analysis of particle A in Fig.6c (d)
Fig.7 Stress-strain curves of the pre-aged alloys in the different directions
Alloy
Direction
Yield strength / MPa
Ultimate tensile strength / MPa
Elongation / %
n
R
No.1
Longitudinal
113.2
236.6
26.30
0.312
0.725
Transverse
104.7
223.4
24.93
0.323
0.649
No.2
Longitudinal
133.0
269.2
25.73
0.298
0.700
Transverse
124.9
253.4
26.01
0.302
0.661
No.3
Longitudinal
161.8
305.6
25.37
0.288
0.645
Transverse
157.4
298.9
25.84
0.289
0.644
Table 2 Mechanical properties of the pre-aged alloys in the different directions
Fig.8 SEM images of three alloys after tensile fracture in the transverse direction and EDS analysis (1)No.1 alloy (b) No.2 alloy (c) No.3 alloy (2)(d) BE-SEM image of No.3 alloy (e) EDS analysis of particle A in Fig.8d
Fig 9 OM images of alloys No.1 (a, d), No.2 (b, e) and No.3 (c, f) after tensile fracture in longitudinal (a~c) and transverse(d~f) directions
Alloy
Direction
Initial thickness / mm
Final thickness / mm
Ra / mm
rmin
No.1
Longitudinal
0.966
0.620
0.346
0.734
Transverse
0.998
0.700
0.298
1.013
No.2
Longitudinal
1.121
0.680
0.441
0.361
Transverse
1.089
0.710
0.379
0.583
No.3
Longitudinal
1.082
0.780
0.302
0.987
Transverse
1.081
0.880
0.201
1.985
Table 3 Minimum bend radius before cracks (rmin) of three alloys bended in the different directions
Fig 10 Schematics of bending processes for Al-Mg-Si-Cu alloys without Fe-rich particle (a) and with high concentration of Fe-rich particles (b)
[1]
Miller W S, Zhuang L, Bottema J, Wittebrood A J, De Smet P, Haszler A, Vieregge A.Mater Sci Eng, 2000; A280: 37
[2]
Wang D.Shanghai Nonferrous Met, 2013; 34(3): 130
[2]
(王丹. 上海有色金属, 2013; 34(3): 130)
[3]
Wang M J, Huang D Y, Jiang H T.Heat Treatment Met, 2006; (09): 34
[3]
(王孟君, 黄电源, 姜海涛. 金属热处理, 2006; (09): 34)
[4]
Sun J.Tech Educ, 2010; (02): 26
[4]
(孙静. 技术与教育, 2010; (02): 26)
[5]
Liu Y W, Wang S W.Auto Engineer, 2011; (02): 50
[5]
(刘伟燕, 王书伟. 汽车工程师, 2011; (02): 50)
[6]
Zhang Q X, Guo M X, Hu X Q, Cao L Y, Zhuang L Z, Zhang J S.Acta Metall Sin, 2013; 49: 1604
