Quantitative Characterization of Processing-Microstructure-Properties Relationships in Pressure Die-Cast Mg Alloys

Three-dimensional microstructure;Casting defects;Porosity;Process conditions;Pressure die-casting;Magnesium alloys

Lee, Soon Gi ; Materials Science and Engineering

University:Georgia Institute of Technology

Department:Materials Science and Engineering

关键词: Three-dimensional microstructure;    Casting defects;    Porosity;    Process conditions;    Pressure die-casting;    Magnesium alloys;   

Others  :  https://smartech.gatech.edu/bitstream/1853/11552/1/lee_soongi_200608_phd.pdf

美国|英语

来源: SMARTech Repository

【 摘 要 】

The central goal of this research is to quantitatively characterize the relationships between processing, microstructure, and mechanical properties of important high-pressure die-cast (HPDC) Mg-alloys. For this purpose, a new digital image processing technique for automatic detection and segmentation of gas and shrinkage pores in the cast microstructure is developed and it is applied to quantitatively characterize the effects of HPDC process parameters on the size distribution and spatial arrangement of porosity. To get better insights into detailed geometry and distribution of porosity and other microstructural features, an efficient and unbiased montage based serial sectioning technique is applied for reconstruction of three-dimensional microstructures. The quantitative microstructural data have been correlated to the HPDC process parameters and the mechanical properties. The analysis has led to hypothesis of formation of new type of shrinkage porosity called, gas induced shrinkage porosity that has been substantiated via simple heat transfer simulations. The presence of inverse surface macrosegregation has been also shown for the first time in the HPDC Mg-alloys. An image analysis based technique has been proposed for simulations of realistic virtual microstructures that have realistic complex pore morphologies. These virtual microstructures can be implemented in the object oriented finite elements framework to model the variability in the fracture sensitive mechanical properties of the HPDC alloys.