Metals and Materials International

, Volume 9, Issue 1, pp 21–27 | Cite as

Effects of precipitate and dendrite arm spacing on tensile properties and fracture behavior of As-Cast magnesium-aluminum alloys

  • Choong Do Lee
  • Kwang Seon Shin


In the present study, the fracture behavior of Mg17Al12 precipitate and the effect of dendrite arm spacing (DAS) on tensile properties of commercial as-cast AZ91D alloy were discussed. In order to obtain a wide range of DAS, the as-cast specimens were fabricated by various casting processes. With gravity-casting, the inoculation and varous molds were utilized, and the solidification rates of melts were measured at four positions of the cone-type mold. The empirical equation between the solidification rate and DAS was found to the [DAS=82.2εavg. −0.41]. Although the DAS as well as the grain size showed a Hall-Petch relationship with yield strength, the UTS and elongation indicated a parabolic relationship with respect to the variation of DAS. The fracture behavior of the as-cast AZ91D alloy was composed of three stages: (1) plasticity-induced crack initiation at the precipitate by matrix deformation, (2) crack growth through concentration of plastic deformation at the interface between the precipitate and matrix, and (3) agglomeration of cracks formed around the precipitate. The plasticity-induced crack is formed through severe deformation of the α-Mg matrix, and the size of the crack in the precipitate is limited by the thickness of the precipitate. Since the stress intensity level around the crack is lowered with the average diameter of the precipitate, the tensile properties of the ascast alloy could be enhanced by the decrease of the average diameter of the precipitate.


dendrite arm spacing (DAS) tensile property Hall-Petch relationship AZ91D alloy plastic deformation crack initiation precipitate 


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Copyright information

© Springer 2003

Authors and Affiliations

  1. 1.Technical CenterGM Daewoo Auto and Technology (GMDAT)IncheonKorea
  2. 2.School of Materials Science and Engineering Research Institute of Advanced MaterialsSeoul National UniversitySeoulKorea

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