Effect of Samarium on the Microstructure and Corrosion Resistance of AZ91 Magnesium Alloy Treated by Ultrasonic Vibration.

Yang Chen,Zheng Yin,Xiao-Quan Wu,Hong Yan,Zhi Hu,Guo-Hua Zhou

doi:10.3390/ma11112331

Abstract

The effects of samarium (Sm) on the microstructure and corrosion behavior of AZ91 magnesium alloy treated by ultrasonic vibration were investigated by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and electrochemical measurements. The results showed that the addition of Sm resulted in the formation of Al2Sm, which reduced the volume fraction of the β-Mg17Al12 phase and changed its morphology to fine granular. The AZ91–Sm alloys treated by ultrasonic vibration revealed relatively lower weight loss, hydrogen evolution, and corrosion current density values compared to the ultrasonic-treated AZ91 alloy prepared without Sm. Locally, a coarse β phase in the ultrasonic-treated AZ91 alloy accelerated the possibility of micro-galvanic corrosion growing into the matrix. In the prepared AZ91–Sm alloys treated by ultrasonic vibration, the fine β and Al2Sm phases reduced the probability of micro-galvanic corrosion growth and, therefore, formed a uniform corrosion layer on the surface of the alloys.

Highlights

As the lightest metallic materials, magnesium (Mg) and its alloys are useful materials for the aerospace, automobile, and electronic industries [1,2]
The initial microstructures of the alloys treated by ultrasonic vibration are shown in Figure 2a, which shows that the primary phase (α-Mg) wasbyseparated byvibration the relatively coarseinβ-Mg
The size of which shows that the primary phase (α-Mg) was separated by the relatively coarse β-Mg17Al12

Summary

Introduction

As the lightest metallic materials, magnesium (Mg) and its alloys are useful materials for the aerospace, automobile, and electronic industries [1,2]. AZ91 alloys are widely used because of their excellent mechanical properties, including high damping characteristics, excellent electromagnetic shielding, and recyclability [4,5]. Researchers have found that the addition of rare earth elements can purify the melt, refine the microstructure, and strengthen properties such as the strength or hardness at room or elevated temperatures and the corrosion resistance, of Mg alloys [6,7]. The AE (Mg-Al-RE) series of alloys is based on the addition of rare earth elements. These materials exhibit enhanced creep resistance due to the complete inhibition of Mg17 Al12 intermetallic compound and the formation of highly stable Al–RE phases, such as Al2 RE, Al3 RE, or other RE phases [9].

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