Simultaneously improving mechanical properties and corrosion resistance of as-cast AZ91 Mg alloy by ultrasonic surface rolling

Abstract

Mg alloy casting parts commonly suffer from drawbacks of low surface properties, high susceptibility to corrosion, unsatisfactory absolute strength, and poor ductility, which seriously limit their wide application. Here, a surface nanocrystallization technique, i.e., ultrasonic surface rolling (USR), was applied on an as-cast AZ91 Mg alloy sheet to improve its corrosion resistance and mechanical properties. The USR produces double smooth surfaces with Ra 0.036 µm and gradient nanostructured surface layers on the sheet. Due to this special microstructure modification, the USR sheet exhibits 55% and 50% improvements in yield strength and ultimate tensile strength without visibly sacrificed ductility comparable to its untreated counterpart, as well as a 24% improvement in surface hardness. The USR sheet also shows good corrosion resistance in 3.5wt% NaCl aqueous solution. The corrosion current density of the USR sheet reduces by 63% after immersion for 1 h, and 25% after immersion for 24 h compared to that of the untreated counterpart. The enhanced strength and hardness are mainly related to the gradient nanostructure. The improved corrosion resistance is mainly ascribed to the decreased surface roughness, nanostructured surface, and residual compressive stress. The present results state that USR is an effective and attractive method to improve the multiple properties of Mg alloy casting parts, and thus can be used as an additional and last working procedure to achieve high-performance Mg alloy casting parts.

Keywords

Mg alloy / ultrasonic surface rolling / surface nanocrystallization / microstructure / strength / corrosion

References

[1] Song JF, She J, Chen DL, Pan FS. Latest research advances on magnesium and magnesium alloys worldwide. J. Magnes. Alloys, 2020, 8(1): 1.

[2] Zhang Z, Zhang JH, Wang J, Li ZH, Xie JS, Liu SJ, Guan K, Wu RZ. Toward the development of Mg alloys with simultaneously improved strength and ductility by refining grain size via the deformation process. Int. J. Miner. Metall. Mater., 2021, 28(1): 30.

[3] Y.C. Wang, B.Y. Liu, X.A. Zhao, X.H. Zhang, Y.C. Miao, N. Yang, B. Yang, L.Q. Zhang, W.J. Kuang, J. Li, E. Ma, and Z.W. Shan, Turning a native or corroded Mg alloy surface into an anti-corrosion coating in excited CO₂, Nat. Commun., 9(2018), art. No. 4058.

[4] Wu G, Chan KC, Zhu LL, Sun LG, Lu J. Dual-phase nanostructuring as a route to high-strength magnesium alloys. Nature, 2017, 545(7652): 80.

[5] Wu GS, Ibrahim JM, Chu PK. Surface design of biodegradable magnesium alloys—A review. Surf. Coat. Technol., 2013, 233, 2.

[6] Zhang JH, Liu SJ, Wu RZ, Hou LG, Zhang ML. Recent developments in high-strength Mg-RE-based alloys: Focusing on Mg-Gd and Mg-Y systems. J. Magnes. Alloys, 2018, 6(3): 277.

[7] Sun JP, Yang ZQ, Han J, Liu H, Song D, Jiang JH, Ma AB. High strength and ductility AZ91 magnesium alloy with multi-heterogenous microstructures prepared by high-temperature ECAP and short-time aging. Mater. Sci. Eng. A, 2018, 734, 485.

[8] J.P. Sun, B.Q. Xu, Z.Q. Yang, H. Zhou, J. Han, Y.N. Wu, D. Song, Y.C. Yuan, X.R. Zhuo, H. Liu, and A.B. Ma, Achieving excellent ductility in high-strength Mg-10.6Gd-2Ag alloy via equal channel angular pressing, J. Alloys Compd., 817(2020), art. No. 152688.

[9] Zhao X, Yan FF, Zhang ZM, Gao PC, Li SC. Influence of heat treatment on precipitation behavior and mechanical properties of extruded AZ80 magnesium alloy. Acta Metall. Sin., 2021, 34(1): 54.

[10] J.P. Sun, B.Q. Xu, Z.Q. Yang, J. Han, N.N. Liang, Y. Han, J.H. Jiang, A.B. Ma, and G.S. Wu, Mediating the strength, ductility and corrosion resistance of high aluminum containing magnesium alloy by engineering hierarchical precipitates, J. Alloys Compd., 857(2021), art. No. 158277.

[11] Lu K. Gradient nanostructured materials. Acta Metall. Sin., 2015, 51(1): 1.

[12] Chen XH, Lu J, Lu L, Lu K. Tensile properties of a nanocrystalline 316L austenitic stainless steel. Scripta Mater., 2005, 52(10): 1039.

[13] Bahl S, Suwas S, Ungàr T, Chatterjee K. Elucidating microstructural evolution and strengthening mechanisms in nanocrystalline surface induced by surface mechanical attrition treatment of stainless steel. Acta Mater., 2017, 122, 138.

[14] Benafia S, Retraint D, Yapi Brou S, Panicaud B, Grosseau Poussard JL. Influence of surface mechanical attrition treatment on the oxidation behaviour of 316L stainless steel. Corros. Sci., 2018, 136, 188.

[15] Wang PF, Han Z. Friction and wear behaviors of a gradient nano-grained AISI 316L stainless steel under dry and oil-lubricated conditions. J. Mater. Sci. Technol., 2018, 34(10): 1835.

[16] C. Wang, J. Han, J.Y. Zhao, Y.M. Song, J.X. Man, H. Zhu, J.P. Sun, and L. Fang, Enhanced wear resistance of 316 L stainless steel with a nanostructured surface layer prepared by ultrasonic surface rolling, Coatings, 9(2019), No. 4, art. No. 276.

[17] Wang T, Wang DP, Liu G, Gong BM, Song NX. Investigations on the nanocrystallization of 40Cr using ultrasonic surface rolling processing. Appl. Surf. Sci., 2008, 255(5): 1824.

[18] Li L, Kim M, Lee S, Bae M, Lee D. Influence of multiple ultrasonic impact treatments on surface roughness and wear performance of SUS301 steel. Surf. Coat. Technol., 2016, 307, 517.

[19] Wang HB, Song GL, Tang GY. Enhanced surface properties of austenitic stainless steel by electropulsing-assisted ultrasonic surface rolling process. Surf. Coat. Technol., 2015, 282, 149.

[20] Li G, Qu SG, Pan YX, Li XQ. Effects of the different frequencies and loads of ultrasonic surface rolling on surface mechanical properties and fretting wear resistance of HIP Ti-6Al-4V alloy. Appl. Surf. Sci., 2016, 389, 324.

[21] Ghamarian I, Samimi P, Telang A, Vasudevan VK, Collins PC. Characterization of the near-surface nanocrystalline microstructure of ultrasonically treated Ti-6Al-4V using AS-TAR™/precession electron diffraction technique. Mater. Sci. Eng. A, 2017, 688, 524.

[22] Liang Y, Qin HF, Mehra N, Zhu JH, Yang ZN, Doll GL, Ye C, Dong YL. Controllable hierarchical micro/nano patterns on biomaterial surfaces fabricated by ultrasonic nanocrystalline surface modification. Mater. Des., 2018, 137, 325.

[23] Ye YD, Li XP, Sun ZY, Wang HB, Tang GY. Enhanced surface mechanical properties and microstructure evolution of commercial pure titanium under electropulsing-assisted ultrasonic surface rolling process. Acta Metall. Sin., 2018, 31(12): 1272.

[24] Amanov A, Penkov OV, Pyun YS, Kim DE. Effects of ultrasonic nanocrystalline surface modification on the tribological properties of AZ91D magnesium alloy. Tribol. Int., 2012, 54, 106.

[25] Ye H, Sun X, Liu Y, Rao XX, Gu Q. Effect of ultrasonic surface rolling process on mechanical properties and corrosion resistance of AZ31B Mg alloy. Surf. Coat. Technol., 2019, 372, 288.

[26] Song YW, Shan DY, Chen RS, Han EH. Corrosion characterization of Mg-8Li alloy in NaCl solution. Corros. Sci., 2009, 51(5): 1087.

[27] Song G. Recent progress in corrosion and protection of magnesium alloys. Adv. Eng. Mater., 2005, 7(7): 563.

[28] Grimm M, Lohmüller A, Singer RF, Virtanen S. Influence of the microstructure on the corrosion behaviour of cast Mg-Al alloys. Corros. Sci., 2019, 155, 195.

[29] Liu Q, Ma QX, Chen GQ, Cao X, Zhang S, Pan JL, Zhang G, Shi QY. Enhanced corrosion resistance of AZ91 magnesium alloy through refinement and homogenization of surface microstructure by friction stir processing. Corros. Sci., 2018, 138, 284.

[30] Li JR, Jiang QT, Sun HY, Li YT. Effect of heat treatment on corrosion behavior of AZ63 magnesium alloy in 3.5 wt.% sodium chloride solution. Corros. Sci., 2016, 111, 288.

[31] Y. Cubides, A.I. Karayan, D.X. Zhao, L. Nash, K. Xie, and H. Castaneda, New insights on the corrosion mechanism of a peak-aged Mg-9Al-1Zn alloy in a chloride environment, J. Alloys Compd., 840(2020), art. No. 155786.

[32] Moon JH, Baek SM, Lee SG, Seong Y, Amanov A, Lee S, Kim HS. Effects of residual stress on the mechanical properties of copper processed using ultrasonic-nanocrystalline surface modification. Mater. Res. Lett., 2019, 7(3): 97.

[33] Zheng RX, Du JP, Gao S, Somekawa H, Ogata S, Tsuji N. Transition of dominant deformation mode in bulk polycrystalline pure Mg by ultra-grain refinement down to sub-micrometer. Acta Mater., 2020, 198, 35.

[34] Li W, Li DY. Influence of surface morphology on corrosion and electronic behavior. Acta Mater., 2006, 54(2): 445.

[35] Orlov D, Ralston KD, Birbilis N, Estrin Y. Enhanced corrosion resistance of Mg alloy ZK60 after processing by integrated extrusion and equal channel angular pressing. Acta Mater., 2011, 59(15): 6176.

[36] Torbati-Sarraf H, Torbati-Sarraf SA, Poursaee A, Langdon TG. Electrochemical behavior of a magnesium ZK60 alloy processed by high-pressure torsion. Corros. Sci., 2019, 154, 90.

[37] Luo KY, Wang CY, Cui CY, Lu JZ, Lu YF. Effects of coverage layer on the electrochemical corrosion behaviour of Mg-Al-Mn alloy subjected to massive laser shock peening treatment. J. Alloys Compd., 2019, 782, 1058.