Corrosion behaviour of friction stir welded ZM21 magnesium alloy

• Published in: Materials today : proceedings Vol. 46; pp. 1464 - 1469
• Main Authors: Lingampalli, Bhavya, Dondapati, Sreekanth
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 2021
• Subjects: Corrosion; Feed rate; Friction stir welding; Magnesium alloys; Rotational speed; ZM21; ZM21; Rotational speed; Corrosion; Feed rate; Friction stir welding; Magnesium alloys
• ISSN: 2214-7853; 2214-7853
• DOI: 10.1016/j.matpr.2021.03.394

•Process parameters that majorly effect the grain size and development of stresses and strains in weld zones are studied.•In depth analysis of the relationship between grain size and corrosion rate of the weld region were presented.•Contribution type of stresses in the materials in the formation of passive layer and corrosion of the metal. In the present work, the microstructure and corrosion behavior of friction stir welded (FSW) butt joints of Mg-Zn-Mn alloy (ZM21) and their reliance on process parameters such as tool rotational speed and feed were investigated. Friction stir welding was performed on 50 mm × 25 mm × 3 mm plates and different experiments were conducted with varying rotational speed and feed rate of the tool. The phase composition and microstructure of the stir zone and base metal were studied using X-ray diffraction (XRD) and optical microscopy respectively. The corrosion behavior of the stir zone and base metal was evaluated by conducting potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl medium. It was observed that the stir zone had undergone severe plastic deformation leading to a larger reduction in grain size with the crystal orientation changed from prismatic planes (101) and (100) to (002) plane. Both rotational speed and feed rate of the tool seem to have a profound effect on microstructure and corrosion behavior of the stir zone. Higher feed rates at a given rotational speed of the tool reduce the grain size and increase the stresses.The rotational speed of the tool seems to have a significant effect on the types of stresses developed in the stir zone. Furthermore, the corrosion behavior of the stir zone largely depended on the type of stresses produced. Even though the reduction in grain size leads to an increase in corrosion resistance of the stir zone, the Compressive stresses produced in the stir zone seems to be detrimental.