Investigation of Stress Corrosion Cracking Behaviour of Mg-Al-Zn Alloys in Different pH Environments by SSRT Method

Recep Catar,Hikmet Altun

doi:10.1515/chem-2019-0104

Abstract

AbstractIn this study, stress corrosion behaviors of AZ31, AZ61 and AZ91 Mg alloys which contain different amounts of Al were investigated under acidic, basic and neutral environments having chloride ions using Slow Strain Rate Test (SSRT) method. Stress corrosion indexes (ISCC), ultimate tensile strength (UTS) and elongation of AZ31, AZ61, and AZ91 Mg alloys were determined and compared. Slow strain rate test showed that three Mg alloys in basic environments were the least stress corrosion susceptible, while the most stress corrosion susceptible occurred in acidic environments. Also, it has been shown that the stress corrosion indexes of AZ91 Mg alloys are less than AZ31 and AZ61 Mg alloys in all environments. UTS and elongation of AZ61 Mg alloys were higher than those of AZ31 and AZ91 in all media. The fracture of surface images also examined in the scanning electron microscope (SEM) and both intergranular stress corrosion cracking (IGSCC) and transgranular stress corrosion cracking (TGSCC) were observed in all three alloys.

Highlights

Mg alloys have many unique properties such as low density, damping capacity, castability, good thermal conductivity, low heat capacity, outstanding recyclability, excellent biocompatibility and non-toxicity to human body and environment
Stress corrosion resistance of AZ91 Mg alloy is higher than AZ31 and AZ61 Mg alloys
It is evident that as the pH value of the solution decreases in all three alloys, the stress corrosion index increases

Summary

Introduction

Mg alloys have many unique properties such as low density, damping capacity, castability, good thermal conductivity, low heat capacity, outstanding recyclability, excellent biocompatibility and non-toxicity to human body and environment. The effect of pH and chloride ion concentration on corrosion of ZE41 Mg alloy was investigated and observed corrosion of the alloy in NaCl chloride solutions depend on the pH and chloride ion concentration [22]. He et al studied the corrosion and SCC behavior of AZ31B Mg alloy in 3.5 wt.% Na2SO4 solution with different pH values and said that corrosion and stress corrosion increased with increasing pH [23]. The aim of this study is to investigate and compare the stress corrosion behavior of these alloys under acidic, basic and neutral environments which contain chloride ions using Slow Strain Rate Test (SSRT) method. Stress corrosion resistance of AZ91 Mg alloy is higher than AZ31 and AZ61 Mg alloys

Objectives

Methods

Results

Conclusion