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Grain Refinement of Magnesium Alloys by Mg–Zr Master Alloys: The Role of Alloy Chemistry and Zr Particle Number Density

Authors

  • Ming Sun,

    1. National Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University, Shanghai 200240, China
    2. CAST Cooperative Research Centre, Department of Materials Engineering, Monash University, Victoria 3800, Australia
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  • Mark A. Easton,

    Corresponding author
    1. CAST Cooperative Research Centre, Department of Materials Engineering, Monash University, Victoria 3800, Australia
    • CAST Cooperative Research Centre, Department of Materials Engineering, Monash University, Victoria 3800, Australia
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  • David H. StJohn,

    1. CAST Cooperative Research Centre, Centre for Advanced Materials Processing and Manufacturing (AMPAM), School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia
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  • Guohua Wu,

    Corresponding author
    1. National Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University, Shanghai 200240, China
    • National Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University, Shanghai 200240, China
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  • Trevor B. Abbott,

    1. Magontec Ltd, Sydney, New South Wales 2000, Australia
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  • Wenjiang Ding

    1. National Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University, Shanghai 200240, China
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  • The work is sponsored by National Natural Science Foundation of China (No. 51275295), the Australian CAST Co-operative Research Centre, ARC Discovery Grants DP120101672 (DStJ) and DP2010000071 (ME), and Funded Projects of SAST-SJTU Aerospace Advanced Technology Joint Research Centre (No. USCAST2012-15). The authors acknowledge the Monash Centre for Electron Microscopy (MCEM) and thank Dr. Mark Gibson, Mr. Andrew Yob at CSIRO and Mr. Darren Gandel at Monash University for help with experiments.

Abstract

Although refinement of the as-cast grain size of magnesium alloys by Zr is well established commercially, little research has been undertaken to optimize this refinement technology and to quantify the relative performance of different Mg–Zr master alloys. The performance of Mg–Zr master alloys was found to be related to (1) the number density of Zr particles between 1 and 5 µm in size where the master alloy with the largest number density of these particles exhibits the best refinement, and (2) the alloy's growth restriction factor (Q) where a linear relationship between grain size and 1/Q, was found to exist for each master alloy. An equation for predicting grain size based on the Interdependence model was developed. Further, the Interdependence Model was improved to be able to cater for an increasing Zr particle number density with increasing values of Q.

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