Effect of thermal shock process in accelerated environment spectrum on the fatigue life of 7B04-T6 aluminum alloy

Abstract

The effect of thermal shock, in an accelerated-corrosion environment spectrum, on the fatigue and corrosion behavior of 7B04-T6 aluminum alloy, was determined. The environment spectrum consists of two modules, namely: salt-spray corrosion and thermal shock. The effect of thermal shock on the mechanical properties was determined via tensile tests; SEM, DCS, and XRD were used to determine the effect of thermal shock on the corrosion products. In addition, the corrosion resistance of the products was ascertained through electrochemical testing. The results show that the mechanical properties and fatigue life of the aluminum alloy will decline with prolonged thermal shock time. The thermal shock process may result in denser surface corrosion products than those formed on the no thermal shock specimens, and transformation of some Al (OH)₃ into AlOOH. AlOOH may have resulted in improved corrosion resistance and hence a lower decrease in the fatigue life after corrosion, compared with that of the no thermal shock specimen. Repeated corrosion/thermal shock may have delayed further decease in the fatigue life. Therefore, selection of an appropriate equivalent thermal shock temperature and time was essential for designing the environmental spectrum.

Keywords

accelerated corrosion environment spectrum / thermal shock / corrosion / fatigue / aluminum alloy

References

[1] Jiang Z G, Tian D S, Zhou Z T. Load/environment Spectrum of Aircraft Structure[M], 2012 Beijing: Electronic Industry Press.

[2] Liu W T, Li Y H. Evaluation Technique for Calendar Life System of Aircraft Structure[M], 2004 Beijing: Aviation Industry Press.

[3] Dan Z, Muto I, Hara Nobuyoshi. Effects of Environmental Factors on Atmospheric Corrosion of Aluminium and Its Alloys under Constant Dew Point Conditions[J]. Corrosion Science, 2012, 57: 22-29.

[4] Zupanca U, Grumb J. Effect of Pitting Corrosion on Fatigue Performance of Shot-peened Aluminium Alloy 7075-T651[J]. Journal of Materials Processing Technology, 2010, 210: 1197-1202.

[5] Barter SA, Molent L. Fatigue Cracking from a Corrosion Pit in An Aircraft Bulkhead[J]. Engineering Failure Analysis, 2014, 39: 155-163.

[6] Bao R, Zhang Xiang. Fatigue Crack Growth Behaviour and Life Prediction for 2324-T39 and 7050-T7451 Aluminium Alloys under Truncated Load Spectra[J]. International Journal of Fatigue, 2010, 32: 1180-1189.

[7] Zheng S, Yu Q, Gao Z, et al. Loading History Effect on Fatigue Crack Growth of Extruded AZ31B Magnesium Alloy[J]. Engineering Fracture Mechanics, 2013, 114: 42-54.

[8] Sunder R. Spectrum Load Fatigue-underlying Mechanisms and Their Significance in Testing and Analysis[J]. International Journal of Fatigue, 2003, 25: 971-981.

[9] Chen S, Chen Kanghua. Effect of Heat Treatment on Strength, Exfoliation Corrosion and Electrochemical Behavior of 7085 Aluminum Alloy [J]. Materials and Design, 2012, 35: 93-98.

[10] Mohammad A, Mehdi M Shirazabadc. Heat Treatment Effect on Thermo-mechanical Fatigue and Low Cycle Fatigue Behaviors of A356.0 Aluminum Alloy[J]. Materials and Design, 2013, 45: 279-285.

[11] Siddiqui RA, Abdul-Wahab SA. Effect of Aging Time and Aging Temperature on Fatigue and Fracture Behavior of 6063 Aluminum Alloy under Seawater Influence[J]. Materials and Design, 2008, 29: 70-79.

[12] Prasanta K R, Ghosh MM, Ghosh KS. Effect of Interrupted Ageing on Stress Corrosion Cracking (SCC) Behaviour of An Al-Zn-Mg-Cu Alloy[J]. Procedia Material Science, 2014, 5: 1214-1223.

[13] Mohammed N D, Pandey PK, Mukhopadhyay AK. Effect of Aging Treatments on the Kinetics of Fatigue Crack Growth in 7010 Aluminum Alloy[J]. Materials Science and Engineering A, 2006 318-326.

[14] Mitsuhiro O, Shoka Go. Precise Analysis of Effects of Aging on Mechanical Properties of Cast ADC12 Aluminum Alloy[J]. Materials Science and Engineering A, 2015, 638: 208-218.

[15] Liu Y, Wang Z, Ke Wei. Study on Influence of Native Oxide and Corrosion Products on Atmospheric Corrosion of Pure Al [J]. Corrosion Science, 2014, 80: 169-176.

[16] Wang X, Wang J, Fu Congwei. Characterization of Pitting Corrosion of 7A60 Aluminum Alloy by EN and EIS Techniques [J]. Transactions of Nonferrous Metals Society of China, 2014, 24: 3907-3916.

[17] Liu Y, Meng GZ, Cheng YF. Electronic Structure and Pitting Behavior of 3003 Aluminum Alloy Passivated under Various Conditions[J]. Electorchimica Acta, 2009, 54: 4155-4160.