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The Effect of Improved Cooling on the Microstructure and Mechanical Properties of Friction Stir‐Welded Advanced High‐Strength Dual‐Phase Steel
Author(s) -
Mahmoudiniya Mahdi,
Kokabi Amir Hossein,
Goodarzi Massoud,
Kestens Leo A. I.
Publication year - 2021
Publication title -
steel research international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.603
H-Index - 49
eISSN - 1869-344X
pISSN - 1611-3683
DOI - 10.1002/srin.202000253
Subject(s) - materials science , welding , softening , metallurgy , microstructure , ultimate tensile strength , dual phase steel , friction stir welding , butt joint , composite material , martensite , thermal diffusivity , physics , quantum mechanics
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.