The effect of improved cooling on the microstructure and mechanical properties of friction stir-welded advanced high-strength dual-phase steel

Journal article (2021)

Authors

M. Mahmoudiniya Universiteit Gent, Iran University of Science and Technology
Amir Hossein Kokabi Sharif University of Technology
Massoud Goodarzi Iran University of Science and Technology
L.A.I. Kestens Universiteit Gent, Team Kevin Rossi - Mechanical, Maritime and Materials Engineering
Research Group
Team Kevin Rossi (Mechanical, Maritime and Materials Engineering) (TU Delft)
Mechanical properties Friction stir welding Dual-phase steels Electron back scattered diffraction analysis Martensite tempering
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Published Date

2021

Language

English

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Faculty

Mechanical, Maritime and Materials Engineering

Department

Materials Science and Engineering

Research Group

Team Kevin Rossi

Abstract

The heat-affected zone (HAZ) softening is considered one of the most significant challenges during welding of ferrite–martensite dual-phase (DP) steels. In fact, the strain localization in the softened area results in a premature fracture that degrades the mechanical properties of the joint. Herein, the objective is to investigate the effectiveness of improved cooling using a high thermal diffusivity backing plate (BP) to reduce HAZ softening and enhance the mechanical properties of friction stir-welded DP700 steel. Accordingly, friction stir butt welding of DP700 steel was conducted using copper and mild steel BPs. The findings show that the replacement of steel BP with copper significantly reduces the weld temperature. It is also observed that the thermal diffusivity of the BP has a substantial effect on the microstructure development and mechanical properties of the welded joint. Increasing the thermal diffusivity of the BP results in a reduction of HAZ softening from 20 to 7 HV and improving tensile strength and total elongation of the joint by 40 MPa and 6.2%, respectively. Work hardening behavior and absorbed energy before the fracture are significantly improved by the replacement of steel BP with a copper.

Files

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