Effect of Micro Solidification Crack on Mechanical Performance of Remote Laser Welded AA6063-T6 Fillet Lap Joint in Automotive Battery Tray Construction
Abstract
:1. Introduction
2. Materials and Methods
2.1. Welding Procedures
2.2. Weld Morphology Characterisation
2.3. Mechanical Characterization
3. Results and Discussion
3.1. Weld Shape
3.2. Weld Zone Grain Morphology
- (i)
- the energy flux distribution of an oscillated laser beam (Figure 5), E(x, y), computed by Equation (2) [34] shows a ‘M’ shape in the transverse direction, with the peak energy deposition at two turning points of the oscillation path.
- (ii)
- the turbulence of molten material in the rear of the molten pool which is induced by the beam oscillation, disturbs the growth of columnar grains in the mushy zone and promote the formation of equiaxed grains. However, this stirring effect induced by transverse beam oscillation is relatively weak as compared to longitudinal and circular oscillations because the oscillations occur only in front of the molten pool [34].
3.3. Crack Distribution
3.4. Weld Tensile Strength and Fatigue Durability
4. Conclusions
- (1)
- Transverse micro cracks occur along the columnar grain boundaries near fusion lines. Increasing welding speed from 2 m/min to 6 m/min, simultaneously with an increasing laser power for the purpose of good part-to-part gap bridging, did not show any risk of introducing additional transverse micro cracks.
- (2)
- Equiaxed grains were observed in the centre of fusion zones while columnar grains were determined near fusion lines. A reduced welding speed facilitates the formation of equiaxed grains due to the greater deposition of beam energy at two turning points of the beam oscillation path, which results in a more uniform temperature distribution within the fusion zone during subsequent solidification.
- (3)
- Although transverse micro crack remains at similar level for welding speed between 2 m/min and 6 m/min, joint tensile strength can be improved by 30% by welding at 2 m/min compared to 6 m/min. This is attributed to expansion of fusion zone, measured by throat thickness and refinement of columnar grains near fusion lines.
- (4)
- Weld fatigue durability is higher when fatigue failure occurs in weld root instead of fusion zone due to the avoidance of transverse micro cracks. Weld fatigue failure position in this study is greatly influenced by weld shape, represented by weld root angle. A higher weld root angle leads to the transition of fatigue failure from the centre of fusion zone (fusion zone failure mode) to the interface between fusion zone and HAZ (weld root failure mode). The highest weld fatigue durability can be achieved by increasing weld root angle with optimum weld fatigue durability at weld root angle of around 55°.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Chemical Composition Limits | |||||||||
---|---|---|---|---|---|---|---|---|---|
Weight % | Si | Fe | Cu | Mn | Mg | Zn | Ti | Cr | Al |
Minimum | 0.2 | - | - | - | 0.45 | - | - | - | Balance |
Maximum | 0.6 | 0.35 | 0.1 | 0.1 | 0.9 | 0.1 | 0.1 | 0.1 | Balance |
Processing Window | Sx [m/min] | ƒ [Hz] | Oy [mm] | PA [kW] | PB [kW] | PC [kW] | Line Energy [J/mm] |
---|---|---|---|---|---|---|---|
S2-F50 | 2 | 50 | 0.4 | 1.74 | 3.25, 3.13, 2.90, 2.67 | 1.45 | 72.68, 70.88, 67.43, 64.07 |
S4-F100 | 4 | 100 | 0.7 | 2.55 | 5.28, 5.05, 4.81, 4.59 | 2.32 | 57.86, 56.14, 54.34, 52.69 |
S6-F150 | 6 | 150 | 0.3 | 4.52 | 5.80, 5.57, 5.34, 5.10 | 3.48 | 49.00, 47.85, 46.70, 45.50 |
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Sun, T.; Franciosa, P.; Liu, C.; Pierro, F.; Ceglarek, D. Effect of Micro Solidification Crack on Mechanical Performance of Remote Laser Welded AA6063-T6 Fillet Lap Joint in Automotive Battery Tray Construction. Appl. Sci. 2021, 11, 4522. https://doi.org/10.3390/app11104522
Sun T, Franciosa P, Liu C, Pierro F, Ceglarek D. Effect of Micro Solidification Crack on Mechanical Performance of Remote Laser Welded AA6063-T6 Fillet Lap Joint in Automotive Battery Tray Construction. Applied Sciences. 2021; 11(10):4522. https://doi.org/10.3390/app11104522
Chicago/Turabian StyleSun, Tianzhu, Pasquale Franciosa, Conghui Liu, Fabio Pierro, and Dariusz Ceglarek. 2021. "Effect of Micro Solidification Crack on Mechanical Performance of Remote Laser Welded AA6063-T6 Fillet Lap Joint in Automotive Battery Tray Construction" Applied Sciences 11, no. 10: 4522. https://doi.org/10.3390/app11104522
APA StyleSun, T., Franciosa, P., Liu, C., Pierro, F., & Ceglarek, D. (2021). Effect of Micro Solidification Crack on Mechanical Performance of Remote Laser Welded AA6063-T6 Fillet Lap Joint in Automotive Battery Tray Construction. Applied Sciences, 11(10), 4522. https://doi.org/10.3390/app11104522