排序方式: 共有30条查询结果,搜索用时 15 毫秒
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Xinghua Yu Sudarsanam Suresh Babu John C. Lippold Hidenori Terasaki Yu-ichi Komizo 《Metallurgical and Materials Transactions A》2012,43(5):1538-1546
A hybrid in-situ characterization system, which couples the laser scanning confocal microscopy (LSCM) with the time-resolved X-ray diffraction
(TRXRD) measurement with synchrotron radiation, was used to characterize the microstructure evolution during heat-affected
zone (HAZ) thermal cycling of high-strength and blast-resistant steel. The combined technique has a time resolution of 0.3 seconds
that allows for high-fidelity measurements of transformation kinetics, lattice parameters, and morphological features. The
measurements showed a significant reduction in the martensite start transformation temperature with a decrease in the prior
austenite grain size. In addition, the LSCM images confirmed the concurrent refinement of martensite packet size with smaller
austenite grain sizes. This is consistent with dilatometric observations. The austenite grain size also influenced the rate
of transformation (df
m
/dT); however, the measurements from the hybrid (surface) and dilatometric (volume) measurements were inconsistent. Challenges
and future directions of adopting this technique for comprehensive tracking of microstructure evolution in steels are discussed. 相似文献
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Peter Kolmskog Annika Borgenstam Mats Hillert Peter Hedstr?m Sudarsanam Suresh Babu Hidenori Terasaki Yu-Ichi Komizo 《Metallurgical and Materials Transactions A》2012,43(13):4984-4988
In situ simultaneous synchrotron X-ray diffraction and laser scanning confocal microscopy have confirmed that bainite in steels can grow below the martensite start temperature. This observation suggests that the formation curves for bainite in time-temperature-transformation diagrams should be extended below the martensite start temperature. Furthermore, the implication of this observation on the growth mechanism of bainitic ferrite is discussed. 相似文献
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Niyanth Sridharan Paul Wolcott Marcelo Dapino Sudarsanam Suresh Babu 《Science & Technology of Welding & Joining》2017,22(5):373-380
Driven by the interest to weld steel and aluminium in the solid state to prevent intermetallic formation, 9?kW ultrasonic additive manufacturing (UAM) has been used to fabricate Al 6061-4130 steel dissimilar metal builds. In addition, Al 6061-Al-6061 builds were fabricated using similar techniques to provide a baseline for mechanical property measurement. Mechanical testing performed using pushpin testing shows that steel–aluminium dissimilar metal welds fail across multiple layers while Al–Al welds delaminate from the substrate. Multi-scale characterisation indicates that the change in failure morphology is due to the formation of metallurgical bonds in the Al–steel builds. Texture analysis shows identical textures at the interface of Al–steel, Al–Al and Al–Ti joints; showing that the bond formation in all cases relies extensively on plastic deformation across multiple materials. In addition, no changes to the bonding mechanism occurred when the materials used as foils and substrate were swapped. 相似文献
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Jeremy L. Caron Sudarsanam Suresh Babu John C. Lippold 《Metallurgical and Materials Transactions A》2011,42(13):4032-4044
BlastAlloy160 (BA-160) steel, with a nominal composition of Fe-0.05C-3.65Cu-6.5Ni-1.84Cr-0.6Mo-0.1V (wt pct), is strengthened
by Cu-rich precipitates and M2C carbides. This alloy was subjected to several weldability tests to assess its susceptibility to certain weld cracking mechanisms.
Hot ductility testing revealed a liquation cracking temperature range (LCTR) of 148 K (–125 °C), which suggested moderate
susceptibility to heat-affected zone (HAZ) liquation cracking. The enrichment of Ni and Cu was measured along the prior austenite
grain boundaries in the simulated partially melted zone (PMZ) and was consistent with similar enrichment at interdendritic
boundaries of the simulated fusion zone (FZ). Good wetting and penetration of liquid films along the austenite grain boundaries
of the PMZ was also observed. Associated with that finding were thermodynamic calculations indicating a completely austenitic
(face-centered cubic) microstructure at elevated temperatures. In testing to determine reheat cracking susceptibility, ductility
values of 41 to 78 pct RA were established for the 723 K to 973 K (450 °C to 700 °C) temperature range. The good ductility
values precluded susceptibility to reheat cracking according to the test criterion. Dilatometric measurements and thermodynamic
calculations revealed the formation of austenite in the reheat cracking temperature range, which was attributed to the high
Ni content of the BA-160 alloy. 相似文献
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Yousub Lee Mark Nordin Sudarsanam Suresh Babu Dave F. Farson 《Metallurgical and Materials Transactions B》2014,45(4):1520-1529
Ni superalloys are widely used for hot section components in jet engines because they are very resistant to corrosion and maintain reasonably high strength at elevated temperature. However, the repair cost of the parts is high, partly due to the complexities of process variable optimization and control in laser cladding. In particular, optimizing the process parameters by experiments is time-consuming and costly. The microstructure and properties of the metal deposit are significantly influenced by values temperature gradient G and solidification rate R at the weld pool solidification boundary. Optimized values can help to reduce defects and improve properties of laser deposits. Optimization is hindered by the fact that the clad melt pool is hot and small, making in situ measurement of such solidification conditions difficult. Numerical simulation of the laser deposition process is a possible alternative to experimental measurement to obtain values of clad solidification parameters. In this investigation, G and R values at the weld pool solidification boundary were obtained from a three dimensional numerical simulation of laser deposition process and melt pool. The primary dendrite arm spacing and cooling rate of the deposited material were then correlated to these solidification conditions. 相似文献
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