Metallurgical Engineering

Metallurgical Engineering

Effect of heat input on microstructure and mechanical properties of AZ91 magnesium alloy with using GTAW process

Document Type : Research Paper

Authors
Farzad Rafiee
Alireza Khodabandeh
Bahram Nami
N. Bani Mustafa arab4
Abstract
In this study, the effect of heat input on microstructure and mechanical properties of magnesium alloy, AZ91, were investigated. The butt welding was carried out at three different heat inputs (269, 452, and 657 J/mm), using a tungsten arc welding process under the protection of inert gas (GTAW). Microstructure observation with optical (OM) and scanning electron, microscopes (SEM) showed that with an increase of the heat input, the grains both in the fusion zone and the heat-affected zone coarsen and the width of the heat-affected zone increased. Moreover, an increase of the heat Input up to 657 J/mm resulted in a decrease of the continuous β-Mg17Al12 phase and an increase of the granular (particularly in weld area) and randomly dispersed. The results of tensile tests show that at high heat input the welding strength will decrease to 114 MPa, due to creation of gas voids in the welding area. This value is 21% less than that observed for lower heat input (269 J/mm).
Keywords
AZ91 magnesium alloy
Heat input
tungsten arc welding process
Microstructure
Mechanical properties
Fractography
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  • Receive Date 23 September 2014