טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentEshed Eyal
SubjectThe Influence of Compositional Changes on the
Amorphization Ability of Mg-Zn-Sm and
Mg-Y-La Alloys
DepartmentDepartment of Materials Science and Engineering
Supervisor Professor Emeritus Menachem Bamberger
Full Thesis textFull thesis text - English Version


Abstract

Magnesium alloys have long been a subject of interest due to their very low specific weight; however, the wide-spread use of magnesium alloys remains hindered by the relatively low mechanical properties and low corrosion resistance these alloys possess. Manufacturing Mg alloys in their amorphous state alters their microstructure so that it contains a single disorderly phase which is expected to improve both the corrosion resistance and the mechanical properties.

The aim of this work was to study the influence that the variation in solute atoms and contents had on the overall tendency of Mg alloy systems to undergo amorphization under rapid solidification conditions, namely, their glass-forming ability. This was achieved by inspecting seven different rapidly-solidified Mg alloys belonging to two innovative alloy systems - Mg-Zn-Sm and Mg-Y-La. The selection of these two unique systems was based on theoretical guidelines for high glass-forming ability that were formulated by researchers throughout the years.

It was revealed that Mg73.6Zn22.1Sm4.3 and Mg86Y9.5Cu2.5La2 had the highest glass-forming ability in their respective alloy systems. Both X-ray diffraction spectra exhibited amorphous patterns without appreciable overlapping peaks. The differential scanning calorimetry spectrum of Mg73.6Zn22.1Sm4.3 displayed a glass transition and three crystallization peaks at 115°C, 131°C, 226°C and 361°C respectively while the DSC spectrum of Mg86Y9.5Cu2.5La2 displayed a glass transition and two crystallization peaks at 161°C, 191°C and 282°C respectively. In order to account for the variation in the glass-forming ability of all inspected alloys, a quasi-ternary spinodal-like decomposition model was proposed. The model, considering both thermodymanic and kinetic aspects, was able to accurately rank the experimental alloys by their glass-forming ability and even predict the high glass-forming ability of another alloy - Mg71Zn28Nd.