Korean Journal of Metals and Materials (대한금속재료학회지)

The Korean Institute of Metals and Materials (대한금속재료학회)
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Microfracture Mechanism of Squeeze Cast AZ51-xSn Magnesium Alloys

용탕단조법으로 제조된 AZ51-xSn 마그네슘 합금의 미세파괴기구

  • Kim, Byeong Ho (Dept. of Materials Science and Engineering, Pusan National University) ;
  • Do, Jeonghyeon (Center for Advanced Aerospace Materials, Pohang University of Science and Technology) ;
  • Lee, Sunghak (Center for Advanced Aerospace Materials, Pohang University of Science and Technology) ;
  • Park, Ikmin (Dept. of Materials Science and Engineering, Pusan National University)
  • 김병호 (부산대학교 재료공학과) ;
  • 도정현 (포항공과대학교 항공재료연구센터) ;
  • 이성학 (포항공과대학교 항공재료연구센터) ;
  • 박익민 (부산대학교 재료공학과)
  • Received : 2009.08.10
  • Published : 2009.12.20
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Abstract

A study was made of the effects of a Sn addition on the microstructure and microfracture mechanism of squeeze cast AZ51-xSn magnesium alloys. Microstructural observation, in situ fracture testing, and fractographic observations were conducted on these alloys to clarify the microfracture process. The microstructural analyses indicated that $Mg_2Sn$ particles as well as $Mg_{17}Al_{12}$ particles precipitated mainly along the solidification cell boundaries; the volume fraction of these hard particles increased as the amount of added Sn increased, with increased the strength. From in situ fracture observations of the AZ51-7Sn alloy, coarse precipitates located on the cell boundaries worked as easy crack propagation sites and caused abrupt intercellular fracturing. On the other hand, the overall fracture properties of the AZ51-3Sn alloy improved because crack propagation proceeded into the Mg matrix rather than into the cell boundaries as twins developed actively, as confirmed by an R-curve analysis. These findings suggest that the addition of 3~5 wt.% Sn is effective in improving both the tensile and fracture properties on the basis of well-developed twins, the blocking of crack propagation, and crack blunting.

Keywords

Acknowledgement

Supported by : 한국과학재단, 과학기술부

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