Microstructure and Mechanical Performance of TIG Welded Joints in Automotive Aluminum Radiators

Literature Overview

This paper by Zeng Zhu and Ye Jiafei (Chongqing Industry Polytechnic College, 2017) investigates the microstructure and tensile properties of tungsten inert gas (TIG) welded joints on aluminum alloy sheets used in automotive radiators. The study compares three filler metal options: ER5183 wire, 5083 aluminum scrap, and a simulated ER5183 wire. The research is supported by the Chongqing Education Commission New Technology Promotion Project (2013-29) and published in Casting Technology (Vol. 38, No. 11, pp. 2724-2725).

Core Technical Findings

The authors systematically evaluated weld surface quality, microstructural characteristics, and tensile strength across three filler metal configurations. The key conclusions are summarized below:

Filler Metal	Surface Quality	Crack Formation	Porosity/Inclusions	Tensile Performance
ER5183 wire	Good bead formation	None observed	Minimal	Best
5083 aluminum scrap	Acceptable	None reported	Moderate	Second-best
Simulated ER5183 wire	Poor surface profile	Obvious surface cracks	Numerous porosity and inclusions	Worst

Technical Analysis of Filler Metal Selection

The selection of filler metal in TIG welding of aluminum alloys is governed by several metallurgical considerations. ER5183 is an Al-Mg alloy containing approximately 4.0-5.0% Mg, designed specifically for welding 5083 base metal. Its composition closely matches the base material, minimizing dilution-related cracking susceptibility in the weld metal. The absence of cracks and superior mechanical properties when using ER5183 confirms that proper filler/base metal compatibility is the dominant factor in achieving sound welds.

The use of 5083 scrap as filler metal produced acceptable but inferior results. This is attributed to the lack of precise compositional control inherent in commercial wire products. Scrap material may contain variable oxide content, surface contamination, and inconsistent Mg distribution, all of which degrade weld quality. The presence of oxide films on scrap surfaces introduces inclusions during the melting process, which act as stress concentrators.

The simulated ER5183 wire performed poorly, exhibiting surface cracking and significant porosity. This likely indicates that the simulated wire deviated from the true ER5183 composition—possibly in terms of Mg content, grain refiner additions, or deoxidizer levels. The surface cracks suggest hot cracking susceptibility, which in aluminum alloys is typically associated with high Mg content in the solidification range or inadequate deoxidation. Porosity formation points to insufficient shielding gas coverage or contamination of the filler wire surface.

Engineering Practice Implications

For automotive radiator manufacturers, this study reinforces a critical principle: the use of certified, specification-compliant filler wire (such as ER5183 per AWS A5.10) is non-negotiable for structural aluminum welds. The cost savings from using scrap material or non-certified alternatives are trivial compared to the risk of field failures. Radiator joints are subjected to cyclic thermal loading, vibration, and coolant pressure; any porosity or microcrack initiation site can lead to fatigue failure under service conditions.

Recommended Process Parameters for Aluminum Radiator TIG Welding

Parameter	Recommended Range	Rationale
Base metal	5083-H321 or 5083-H111	Standard radiator grade
Filler wire	ER5183 (AWS A5.10)	Composition match, low cracking
Shielding gas	100% Ar or 99% Ar/1% CH4	Prevent oxidation, improve wetting
Travel speed	300-500 mm/min	Balance penetration and distortion
Current	AC 80-120 A	Adequate for 2-3 mm thickness
Frequency	60-100 Hz	Cathodic cleaning effect

The AC welding mode is essential for aluminum alloys because the cathodic cleaning effect during the negative half-cycle removes the refractory Al2O3 oxide layer from the weld pool surface. Without this cleaning action, oxide inclusion formation is inevitable, leading to porosity and reduced joint strength.

Study Insights and Reflections

The experimental design in this paper, while straightforward, addresses a practical problem that many small and medium-sized radiator manufacturers face daily: the temptation to reduce filler wire costs through substitution. The results provide clear evidence that such shortcuts are counterproductive. From a quality management perspective, this study supports the implementation of a strict material traceability system for filler metals, requiring mill certificates and periodic chemical analysis of incoming wire batches.

The observation that simulated ER5183 wire produced the worst results also highlights the importance of supplier qualification. In engineering procurement, relying solely on nominal composition claims without verifying actual wire chemistry through spectroscopic analysis can lead to costly quality escapes. A robust incoming inspection protocol should include optical emission spectroscopy (OES) verification of Mg, Fe, Si, and Mn content against AWS A5.10 specifications.