Abstract
In this study, dissimilar sheets including AA3003 aluminum and A441 AISI steel were welded via cooling-assisted friction stir welding (FSW). Three different cooling mediums including forced CO2, forced water, and forced air were employed, and a non-cooled sample was processed to compare the cooling-assisted condition with the traditional FSW condition. The highest cooling rate belongs to CO2 and the lowest cooling rate belongs to the non-cooled sample as FSW. The best macrograph without any segregation at interface belongs to the water-cooled sample and the poorest joint with notable segregation belongs to the CO2 cooling FSW sample. The CO2 cooling FSW sample exhibits the smallest grain size due to the suppression of grain growth during dynamic recrystallization (DRX). The intermetallic compound (IMC) thickening was suppressed by a higher cooling rate in CO2 cooling sample and just Al-rich phase was formed in this joint. The lowest cooling rate in the FSW sample exhibits formation of the Fe rich phase. The IMC layers were thicker at the top of the weld due to closeness with the heat generation source. The water cooling sample exhibits the highest tensile strength due to proper mechanical bonding simultaneously with optimum IMC thickness to provide appropriate metallurgical bonding. Fractography observation indicates that there is a semi-ductile fracture in the water cooling sample and CO2 cooling sample exhibits more brittle fracture. Hardness evaluation reveals that the higher the cooling rate formed, the higher the hardness in stir zone, and hardness changes in the aluminum side were higher than the steel side.
Highlights
Al3xxx series is one of the aluminum alloys series that has more strength than theAl1xxx
The friction stir welding (FSW) process was used for aluminum alloys [6,12,13,14]; over time, the capacity and potential of FSW proved that this method could be employed for aluminum alloys, and for other purposes such as joining of similar and dissimilar polymeric and metallic materials [15,16,17,18,19,20,21,22,23,24,25]
The results show that a higher cooling rate can reduce grain size due to suppressing completeness of grain growth kinetics as discussed in the whole of this section
Summary
Al3xxx series is one of the aluminum alloys series that has more strength than the. Al1xxx. The majority of earlier research on high melting point materials focused on the interaction between the process parameters, the final weld microstructure, and the correlative mechanical features [31,32]. These studies and examinations have indicated that the cooling rate and peak temperature have significant effects on the joint mechanical features. There have been new studies on the effect of rapid cooling on FSW, such as the case study of Godasu et al [36] which reported a significant advancement of 460 MPa in the yield strength of the joint with a very low reduction of ductility (3%), after cryocooling Al 5083 alloy to 90% thickness reduction. These optimum parameters help decrease the number of experimental tests like examine various ranges of FSW tool rotational speed, traveling speed, tool tilt angle, tool offset, tool pin profile, and other parameters
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