Papers by Author: Y.H. Park

Abstract: The effect of Al content on the microstructural characteristics, tensile and creep properties of Mg-xAl-Zn alloy was investigated. The molten Mg-(3~11)Al-Zn alloys of 700°C were poured into the permanent mould designed to prepare the specimens used in this study. Tensile and creep tests were carried out for each Mg-Al based alloys. Results show that creep resistance decreased while tensile strength improved with increasing Al contents. Microstructural study revealed that morphology and distribution of non equilibrium Mg17Al12 phase is main factor determining the tensile and creep properties of as cast Mg-xAl-Zn alloys. The final purpose of this study is to construct the database of already used Mg-Al based alloy and to develop the heat resistant magnesium alloys to apply transportation systems such as automobile.

Abstract: The effects of tin (Sn) and strontium (Sr) additions on the microstructure and creep properties of Mg-5Al-2Si (AS52) alloys were investigated. Results showed that the addition of Sn did not affect the morphology of secondary phase Mg2Si particles but induced the fine and uniform precipitation of thermally stable Mg2Sn at the grain boundary in the AS52 alloys. However, the morphology modification of the secondary phase Mg2Si particles from Chinese script shape to refined polygonal shape was greatly affected by the addition of Sr. Tensile strength and creep resistance were improved and tensile elongation was also increased in the modified alloy with addition of both Sr and Sn. Sn is the effective element for precipitating thermally stable Mg2Sn finely and uniformly at the grain boundary and Sr is the effective element for refining microstructure. Therefore both Sn and Sr are effective for modifying the microstructure and improving the creep properties of AS52 alloys.