Diagnosis and Analysis of Oxide Films in Cast Magnesium Alloys by Ultrasonic-Vibration Treatment

Abstract

Magnesium alloys with low density are important light metals, widely used in the aerospace and automotive industries and in the manufacture of communication devices, consumer-electronics appliances and computers products in recent years. However magnesium and magnesium alloys are the most reactive metals so that oxide films easily form on them during the melting or pouring process. These films are difficult to observe by optical micrograph. In this study we propose a simple method to observe oxide films entrapped in cast magnesium alloys. The oxide films are fractured as a result of cavitation erosion on the sample surface that occurs during ultrasonic-vibration treatment. The eroded areas become visible as differently shaped foggy marks. This method of observing and identifying foggy marks is shown to be useful in the diagnosis of oxide films in cast magnesium alloys. In addition, the presented method in the diagnosis of oxide films that formed on magnesium and aluminum alloys are also compared.