• Journal of Welding and Joining
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• v.15 no.5
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• pp.46-55
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• 1997

This study has evaluated the liquation cracking behavior in the heat affected zone of several Ni base superalloys (Incoloy 825, Inconel 718 and Inconel 600). 304 and 310S austenitic stainless steels were also included for comparison. In addition, the mechanism of liquation cracking in the HAZ was postulated based on the extensive microstructural examinations with SEM, EDAX and TEM. The liquation cracking resistance of Ni base alloys was found to be far inferior to that of austenitic stainless steels. The liquation cracking of Incoloy 825 and Inconel 718 was believed to be closely related with the Laves-austenite(Ti rich in 825 and Nb rich in 718) and MC-austenitic eutectic phases formed along the grain boundaries by constitutional liquation and incipient melting under rapid welding thermal contraction. Further, liquation cracking resistance of the HAZ was dependent not only upon the type and amount of low melting phases but also on the grain size.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.244-249
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• 2002

The purpose of this study is to develope the prediction method of liquation crack initiation in HAZ of laser weldment. Thermal two dimensional strain analyses were performed by FEM for bead-on-plate welding in order to obtain the plastic strain at elevated temperature in HAZ of the laser weldment. From these results, it became clear that the plastic strain at elevated temperature affected liquation crack initiation in HAZ, and it could be proposed that the critical strain, which controlled liquation crack initiation, existed. Moreover, an attempt was made to develop thermal and dynamic three dimensional strain analysis method for the laser weldment in order to obtain the plastic strain at elevated temperature in HAZ of the laser weldment in more detail and precisely.

• Journal of Welding and Joining
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• v.21 no.2
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• pp.82-88
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• 2003

The bonding phenomenon and mechanism in the transient liquid phase bonding(TLP Bonding) of directionally solidified Ni base superalloy, GTD-111 was investigated. At the bonding temperature of 1403K, liquid insert metal was eliminated by isothermal solidification which was controlled by the diffusion of B and Si into the base metal and solids in the bonded interlayer grew epitaxially from mating base metal inward the insert metal. The number of grain boundaries formed at the bonded interlayer was corresponded with those of base metal. The liquation of grain boundary and dendrite boundary occurred at 1433K. At the bonding temperature of 1453K which is higher than liquation temperature of grain boundary, liquids of the Insert metal were connected with liquated grain boundaries and compositions in each region mixed mutually. In Joints held for various time at 1453t phases formed at liquated grain boundary far from the interface were similar to those of bonded interlayer. With prolonged holding time, liquid phases decreased gradually and liquids of continuous band shape divided many island shape. But liquid phases did not disappeared after holding for 7.2ks at 1453k. Isothermal solidification process at the bonding temperature which is higher than the liquation temperature of the grain boundary was controlled by diffusion of Ti to be result in liquation than B or Si. in insert metal. (Received January 15, 2003)

• Proceedings of the KWS Conference
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• 2008.05a
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• pp.7-7
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• 2008

• Journal of Welding and Joining
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• v.14 no.3
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• pp.93-104
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• 1996

This study evaluated relative hot cracking susceptibility of commercial aluminum alloy welds, and then suggested possible mechanisms operated in the weld fusion zone and in the heat affected zone based on the observed cracking morphologies, fractography and microstructural features. The fusion zone solidification cracking was found to be mainly due to a microsegregation of Cu, Si, and Mg in grain boundaries, while liquation cracking in the HAZ was by the incipient melting of the segregated grain boundaries and the consitutional liquation of large aging precipitates and intermetallic compounds in the partially melted zone adjacent to the fusion line which experienced a rapid thermal excursion during welding.

• Journal of Welding and Joining
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• v.31 no.3
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• pp.31-38
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• 2013

The transition of serrated grain boundary and its effect on liquation behavior in the simulated weld heat-affected zone (HAZ) have been investigated in a wrought Ni-based superalloy Alloy 263. Recently, the present authors have found that grain boundary serration occurs in the absence of adjacent coarse ${\gamma}^{\prime}$ particles or $M_{23}C_6$ carbides when a specimen is direct-aged with a combination of slow cooling from solution treatment temperature to aging temperature. The present study was initiated to determine the interdependence of the serration and HAZ property with a consideration of this serration as a potential for the use of a hot-cracking resistant microstructure. A crystallographic study indicated that the serration led to a change in grain boundary character as special boundary with a lower interfacial energy as those terminated by low-index {111} boundary planes. It was found that the serrated grain boundaries are highly resistant to boron enrichment, and suppress effectively grain coarsening in HAZ. Furthermore, the serrated grain boundaries showed a higher resistance to susceptibility of liquation cracking. These results was discussed in terms of a significant decrease in interfacial energy of grain boundary by the serration.

• Journal of Environmental Impact Assessment
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• v.19 no.2
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• pp.107-116
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• 2010

In this research potential liquation of contaminants from surrounding soil to a reservoir in an island was studied to investigate the cause and route of contamination of Baengyeong-myeon reservoir. Soil of Baengyeong-myeon reservoir consists of $SiO_2$ and has a high iron content because of geological characteristics of its country rock. From the field investigation and simulation study it was found that highly accumulated carbon content in the reservoir sediment was incurred from ground water, which provides a good habitat for microbes. And the liquation, the cause of organics growth, occurs mainly on the bottom of the reservoir consisting marine clay layer once used as farmland. So dredging of the sediment of reservoir and replacing with valley soil is suggested to prevent continuous contamination of a reservoir in an island due to COD production.

• Proceedings of the KWS Conference
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• 1998.05a
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• pp.52-55
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• 1998

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.204-207
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• 2000

• Journal of Welding and Joining
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• v.28 no.5
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• pp.28-34
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• 2010