Page 1 of 4 Heat Affected Zone in Welded Metallic Materials Zakaria Boumerzoug* Mechanical Engineering Department, University of Biskra, Algeria ISSN: 2692-5397 DOI: 10.33552/MCMS.2020.03.000566 Modern Concepts in Material Science Mini Review Copyright © All rights are reserved by Zakaria Boumerzoug This work is licensed under Creative Commons Attribution 4.0 License MCMS.MS.ID.000566. *Corresponding author: Zakaria Boumerzoug, Mechanical Engineering Department, LMSM, University of Biskra, Algeria. Received Date: October 16, 2020 Published Date: November 04, 2020 Abstract Welding is used extensively for pipe welding, aerospace, aviation, biomedical implants, fabrication of race cars, choppers, etc. Generally, the metallurgy of the welded joint performed by thermal fusion joining process can be categorized into two major regions, the fusion zone (FZ) and the heat-affected zone (HAZ). The heat-affected zone (HAZ) is a region that is thermally affected by the welding treatment. The main difficulty associated with welding is the prevention of unexpected deterioration of properties as a result of the microstructure evolutions which reduce the resistance to brittle fracture in the heat-affected zone (HAZ). Properties of the HAZ are different from those of the base material. According to the literature, the HAZ is the most problematic area in the high strength steels weld. For this reason, many research works investigated this critical zone in welded joint. The main research questions and results related to the HAZ will be presented. Keywords: Welding; Heat affected zone; Microstructure; Mechanical properties; Thermal cycle simulation Abbreviations: HAZ: Heat Affected Zone; Hv: Hardness Vickers; FZ: Fusion Zone; BM: Base Metal; T-HAZ: True Heat Affected Zone; PMZ: Partially Melted Zone Introduction Welding is a process of joining materials into unique piece. Welding is an enabling technology applied across almost all industries, from micro-joining of medical devices, electronics and photonics, to larger scale applications such as bridges, buildings, ships, rail, road transport, pressure equipment and pipelines [1]. Welding processes are divided into thermal fusion joining processes and solid-state joining processes. The most common processes of welding are thermal fusion joining processes such electric arc welding. This welding method is performed under high temperature conditions. Heat generated during welding induces an important temperature gradient in and around the welded area. Generally, the metallurgy of the welded joint can be divided into two main zones, the fusion zone (FZ) and the heat-affected zone (HAZ). The HAZ is a zone which is outside the FZ of the welded joint that is thermally affected by the welding treatment. The HAZ is considered as a transition zone, because it is composed with the microstructure of the BM and the FZ. The properties of the HAZ are very important after performing a weld, because it is considered as a weaker zone, i.e.; the area of failure when the welded metal is submitted to hard conditions. For this reason, it is important to understand this critical zone in welded joint. Microstructures of HAZ The HAZ is the unavoidably heat treated area in the parent metal near the fusion zone during welding where structural transformations occur [2]. HAZ formed during welding is an area in