Grain-refining of Mg alloys by nanoscaled tin particles

A method was developed which allows grain-refining of Mg alloys via casting from Mg melts containing nanoscale TiN particles. AZ91 and AZ31 precursor materials loaded with 10 to 13 vol.-% of TiN nano particles was generated and added to pure AZ91 and AZ31 melts, respectively. The dispersed particles in the melt act as nucleation sites of Mg grains during solidification. The cast materials containing TiN show refined grains and less and smaller dendrites in comparison to the pure Mg alloys cast under the same metallurgical conditions. The grain refined materials contain about 0.6 vol.-% of TiN nano particles. The precursor materials were analyzed by X-ray diffraction and differential thermo analysis. It was shown that TiN nano particles are stable on AZ91 melts for several hours at 700 degrees C. This is a requirement to gain a heterogeneous nucleation of Mg grains on TiN seeds. The results are discussed.