Mechanism of grain refinement induced by laser shock processing in AZ31 magnesium alloy

Xingcheng Li; Yongkang Zhang; Qinglai Zhang; Jinyu Zhou; Yalin Lu; Jufang Chen

doi:10.1007/s11595-016-1418-4

Journal of Wuhan University of Technology Materials Science Edition ›› 2016, Vol. 31 ›› Issue (3) : 611 -615. DOI: 10.1007/s11595-016-1418-4

Metallic Materials

Mechanism of grain refinement induced by laser shock processing in AZ31 magnesium alloy

Author information +

History +

PDF

Abstract

In order to study the mechanism of grain refinement induced by laser shock processing (LSP) in AZ31 magnesium alloy, the specimens were processed with Nd:glass pulse laser shocking and the microstructures of LSP specimens near the surface were examined by optical microscopy and transmission electron microscopy. Optical microstructure pictures show that the size of grains formed in the top surface layer is about 4-6 μm, which is obviously different from the original grains (with an average size of 20-30 μm) in the substrate in AZ31 magnesium alloy. Transmission electron microscopic observations show that the grain refinement process of AZ31 alloy by laser shock processing includes three stages. At the early stage of LSP, the lower strain and strain rate activates the three dislocation slip systems which include basal plane system, prismatic plane system and pyramidal plane system, with the deformation governed mainly by dislocation. At the intermediary stage, dislocation slip is hindered at grain boundaries and becomes more difficult to continue during LSP. Then, parallel twins appear, which divide the original coarse grains into finer twin platelets. Finally, high-density dislocation walls are formed and subdivide twins into sub-grains. Dynamic recrystallization occurs in the process of further deformation and forms recrystallized grains when strain energy reaches the value needed by recrystallization, which leads to refinement of the grains in the top surface layer.

Keywords

laser shock processing / magnesium alloy / grain refinement / twin / dynamic recrystallization

Cite this article

Download citation ▾

Xingcheng Li, Yongkang Zhang, Qinglai Zhang, Jinyu Zhou, Yalin Lu, Jufang Chen. Mechanism of grain refinement induced by laser shock processing in AZ31 magnesium alloy. Journal of Wuhan University of Technology Materials Science Edition, 2016, 31(3): 611-615 DOI:10.1007/s11595-016-1418-4

登录浏览全文

4963

注册一个新账户忘记密码

References

Publishing order | Descend order by publishing year | Descend order by cited within

[1]	Srinivasan P B, Blawert C, Dietzel W. Effect of Plasma Electrolytic Oxidation Coating on The Stress Corrosion Cracking Behaviour of Wrought AZ61 Magnesium Alloy[J]. Corros. Sci., 2008, 50(8): 2415-2422.

[2]	Zhang Y K, You J, Lu J Z. Effects of Laser Shock Processing on Stress Corrosion Cracking Susceptibility of AZ31B Magnesium Alloy[J]. Surf. Coat. Technol., 2010, 204: 3947-3953.

[3]	Winzer N, Atrens A, Song G. A Aritical Review of the Stress Corrosion Cracking (SCC) of Aagnesium Alloys[J]. Adv. Eng. Mater., 2005, 7: 659-665.

[4]	Ramamurthy S, Atrens A. The Influence of Applied Stress Rate on the Stress Corrosion Cracking of 4340 and 3.5NiCrMoV Steels in Distilled Water at 30 ?[J]. Corros. Sci., 2010, 52(3): 1042-1048.

[5]	Rubio-Gonzãlez C, Ocaña JL, Gomez-Rosas G, et al. Effect of Laser Shock Processing on Fatigue Crack Growth and Fracture Toughness of 6061-T6 Aluminum Alloy[J]. Mater. Sci. Eng. A, 2004, 386: 291-297.

[6]	Lu J Z, Zhang L, Feng A X. Effects of Laser Shock Processing on Mechanical Properties of Fe-Ni Alloy[J]. Mater. Design., 2009, 30: 3673-3680.

[7]	Aung N N, Zhou W. Effect of Grain Size and Twins on Corrosion Behaviour of AZ31B Magnesium Alloy[J]. Corros. Sci., 2010, 52: 589-595.

[8]	Yang C H, Hodgson P D, Liu Q C, et al. Geometrical Effects on Residual Stresses in 7050-T7451 Aluminum Alloy Rods Subject to Laser Shock Peening[J]. J. Mater. Process. Technol., 2008, 201: 303-309.

[9]	Zhang X C, Xu B S, Wang H D. Effect of Graded Interlayer on the Mode I Edge Elamination by Residual Stresses in Multilayer Coatingbased Systems[J]. Appl. Surf. Sci., 2008, 254: 1881-1888.

[10]	Sun H Q, Shi Y N, Zhang M X. Plastic Strain-induced Grain Refinement in the Nanometer Scale in a Mg Alloy[J]. Acta Mater., 2007, 55: 975-981.

[11]	Lu K, Mater J. Nanostructured Surface Layer on Metallic Materials Induced by Surface Mechanical Attrition Treatment[J]. Sci. Eng. A, 2004, 38: 375.

[12]	Wang K, Tao N R, Liu G. Plastic Strain-induced Grain Renement at the Nanometer Scale in Copper[J]. Acta Mater., 2006, 54: 5281-5287.

[13]	Zhu K Y, Vassel A, Brisset F. Nanostructure Formation Mechanism of a-titanium Using SMAT[J]. Acta Mater., 2004, 52: 4101-4107.

[14]	Lu J Z, Luo K Y, Zhang Y K. Grain Refinement Mechanism of Multiple Laser Shock Processing Impacts on ANSI 304 Stainless Steel[J]. Acta Mater., 2010, 58: 5354-5360.

[15]	Gomez-Rosas G, Rubio-Gonzalez C, Ocana J L. High Level Compressive Residual Stresses Produced in Aluminum Alloys by Laser Shock Processing[J]. Appl. Surf. Sci., 2005, 252: 883-890.

[16]	Luo K Y, Lu J Z, Zhang L F. The Microstructural Mechanism for Mechanical Property of LY2 Aluminum Alloy after Laser Shock Processing[J]. Mater. Design, 2010, 31: 2599-2606.

[17]	Matsubara K, Miyahara Y, Horita Z. Developing Superplasticity in a Magnesium Alloy through a Combination of Cxtrusion and ECAP[J]. Acta Mater., 2003, 51: 3073-3080.

[18]	Agnew S R, Horton J A, Lillo T M. Enhanced Ductility in Strongly Textured Magnesium Produced by Equal Chaunel Angular Processing[J]. Scripta Mater., 2004, 50: 377-385.