초음파 미세 표면 냉간단조법(UNSM)을 적용한 AZ31 마그네슘 판재의 단면 미세조직 및 강도 향상 효과 분석 = Through-Thickness Microstructures and Yield Strength Enhancement for AZ31 Mg Sheets Treated by Ultrasonic Nanocrystal Surface Modification

다국어 초록 (Multilingual Abstract)

An ultrasonic nanocrystal surface modification (UNSM) technique was applied to a 1-mm thick AZ31 magnesium sheet. UNSM is a relatively new surface modification technique in which a hard, hemispherical tip (2.38 mm in diameter) strikes the surface at an ultrasonic frequency to induce plastically deformed gradient microstructures and deep compressive residual stresses through the thickness. After the UNSM treatment, the through-thickness microstructures were thoroughly investigated using electron microscopy and electron backscatter diffraction analysis. The through-thickness microstructures revealed zones that were severely deformed (down to 200 µm from the surface) and twin-dominated (200~300 µm deep from the surface). The severely deformed zone consisted of shear banding, grain subdivision and reorientation, due to the strong plastic deformation, accompanied by the formation of { } tensile twins (despite compressive strikes by the hemispherical tip), { }-{ } double twins and { } compression twins. The cause for tensile twinning was examined through a literature survey. In the twin-dominated zone, the twining activity prevailed as the slip activity gradually decayed through the thickness. The UNSM-induced hardness and microstructure enhancement was found to be effective down to about 300~400 μm deep from the surface. Finally, the source of the increase in yield strength after the UNSM treatment of the AZ31 sheet was analyzed, and focused on individual cases of microstructural enhancement in the severely deformed zone and the twin zone, and the compressive residual stress.

참고문헌 (Reference)

1 A. Amanov, 286 : 136-, 2012

2 X. Hou, 78 : 1061-, 2017

3 Z. Wang, 745 : 450-, 2019

4 H.K. Kim, 385 : 300-, 2004

5 K. S. Fong, 137 : 051004-, 2015

6 S. Ishihara, 468 : 214-, 2007

7 M. Jamalian, 149 : 9-, 2019

8 S. M. Baek, 12 : 100821-, 2020

9 A. Amanov, 54 : 106-, 2012

10 B. Wu, 213 : 271-, 2012

11 A. Amanov, 207 : 135-, 2012

12 M. S. Suh, 36 : 769-, 2013

13 A. Gill, 576 : 346-, 2013

14 M. Yasuoka, 218 : 93-, 2013

15 A. Amanov, 64 : 24-, 2013

16 R. Gehrmann, 395 : 338-, 2005

17 N. V. Dudamell, 59 : 6949-, 2011

18 S. Bagherifard, 66 : 93-, 2018

19 A. Yazdanmehr, 13 : 5190-, 2020

20 M. D. Nave, 51 : 881-, 2004

21 M. R. Barnett, 56 : 5-, 2008

22 J. H. Kim, 170 : 11-, 2019

23 S. -G. Hong, 58 : 5873-, 2010

24 Y. Xin, 64 : 986-, 2011

25 A. Chapuis, 7 : 433-, 2019

26 B. Wu, 321 : 318-, 2014

27 R. Xin, 700 : 226-, 2017

28 S. Hong, 58 : 5873-, 2010

29 이목영 ; 김재중, "마그네슘 박판 겹치기 이음부의 레이저 용접성에 관한 연구" 대한용접접합학회 37 (37): 293-298, 2019

30 유진영 ; 이명재 ; 문영훈 ; 노유정 ; 이태경, "기계 학습을 활용한 마그네슘 합금의 통전 비선형 온도 예측" 대한금속·재료학회 58 (58): 413-422, 2020

31 박성혁 ; 홍성구 ; 이정훈 ; 이종수, "{10ī2} 쌍정 특성이 AZ31 마그네슘 합금 압연재의 변형거동에 미치는 영향" 한국소성∙가공학회 19 (19): 416-422, 2010

32 Vaira Vignesh Ramalingam ; Padmanaban Ramasamy ; Mohan Das Kovukkal ; Govindaraju Myilsamy, "Research and Development in Magnesium Alloys for Industrial and Biomedical Applications: A Review" 대한금속·재료학회 26 (26): 409-430, 2020

33 김영균 ; 김민종 ; 황유진 ; 김세광 ; 임현규 ; 이기안, "CaO 첨가 AZ31 압출재의 개량된 미세조직이 인장, 고주기 피로 및 피로 균열 전파 특성에 미치는 영향" 대한금속·재료학회 59 (59): 365-373, 2021

34 이병호 ; 김용우 ; 박성혁 ; 이종수, "AZ31 Mg합금의 쌍정 형성에 미치는 초기 집합조직의 영향" 한국소성∙가공학회 16 (16): 467-472, 2007