| Analysis of Microstructure for Resistance Spot Welded TRIP Steels using Atomic Force Microscope |
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Chul Young Choi, ChangWook Ji, Dae-Geun Nam, Jaeho Jang, Soon Kook Kim, Yeong-Do Park |
Correspondence:
Yeong-Do Park,
Email: ypark@deu.ac.kr
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| Abstract |
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The spot welds of Transformation Induced Plasticity (TRIP) steels are prone to interfacial failure and narrow welding current range. Hard microstructures in weld metal and heat affected zone arenormally considered as one of the main reason to accelerate the interfacial failure mode. There fore, detailed observation of weld microstructure for TRIP steels should be made to ensure better weld quality. However, it is difficult to characterize the microstructure, which has similar color, size, and shape using the optical or electron microscopy. The atomic force microscope (AFM) can help to analyze microstructure by using different energy levels for different surface roughness. In this study, the microstructures of resistance spot welds for AHSS are analyzed by using AFM with measuring the differences in average surface roughness. It has been possible to identify the different phases and their topographic characteristics and to study their morphology using atomic force microscopy in resistance spot weld TRIP steels. The systematic topographic study for each region of weldments confirmed the presence of different microstructures with height of 350nmfor martensite, 250nm for bainite, and 150nm for ferrite, respectively. |
| Key Words:
Resistance spot welding, TRIP steels, Atomic force microscope, Scanning electron microscopy, optical microscopy |
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