Metastable liquid phase separation and rapid solidification in a metastable miscibility gap were investigated on the Cu60Co30Cr10 alloy by using the electromagnetic levitation and splat-quenching.It is found that the ...Metastable liquid phase separation and rapid solidification in a metastable miscibility gap were investigated on the Cu60Co30Cr10 alloy by using the electromagnetic levitation and splat-quenching.It is found that the alloy generally has a microstructure consisting of a（Co,Cr）-rich phase embedded in a Cu-rich matrix,and the morphology and size of the（Co,Cr）-rich phase vary drastically with cooling rate.During the electromagnetic levitation solidification processing the cooling rate is lower,resulting in an obvious coalescence tendency of the（Co,Cr）-rich spheroids.The（Co,Cr）-rich phase shows dendrites and coarse spheroids at lower cooling rates.In the splat quenched samples the（Co,Cr）-rich phase spheres were refined significantly and no dendrites were observed.This is probably due to the higher cooling rate,undercooling and interface tension.展开更多
In order to investigate the microstructure evolution and gain complete isothermal solidification time, transient liquid phase （TLP） bonding of IN-738LC superalloy was carried out using powdered AMS 4777 as the fille...In order to investigate the microstructure evolution and gain complete isothermal solidification time, transient liquid phase （TLP） bonding of IN-738LC superalloy was carried out using powdered AMS 4777 as the filler metal. The influence of gap size and bonding time on the joints was investigated. For example, complete isothermal solidification time for 40μm gap size was obtained as 45 min. In the case of lack of completion of isothermal solidification step, the remained molten interlayer cooled in the bonding zone under non-equilibrium condition andγ–γ′ eutectic phase formed in that area. The relationship between gap size and holding time was not linear. With the increase in gap size, eutectic phase width became thicker. In the diffusion affected zone, a much larger amount of alloying elements were observed reaching a peak. These peaks might be due to the formation of boride or silicide intermetallic. With the increase in gap size, the time required for bonding will increase, so the alloying elements have more time for diffusion and distribution in farther areas. As a result, concentrations of alloying elements decreased slightly with the increase in the gap size. The present bi-phasic model did not properly predict the complete isothermal solidification time for IN-738LC-AMS 4777-IN-738LC TLP bonding system.展开更多
An investigation was carried out to assess the applicability of transient liquid phase bonding of two dissimilar super-alloys with different interlayers. The effect of using three types of interlayer such as BNi-2, BN...An investigation was carried out to assess the applicability of transient liquid phase bonding of two dissimilar super-alloys with different interlayers. The effect of using three types of interlayer such as BNi-2, BNi-3, and BNi-9 on microstructure and mechanical properties was studied in the GTD-111/IN-718 system at 1100 ℃ for different bonding time. To determine the compositional changes and microstructure in the joint region, field emission scanning electron microscopy equipped with energy dispersive spectroscopy was utilized. The formation of Ni_(3)B in the athermally solidified zone(ASZ) is controlled by the B content and, accordingly, the morphology of Ni_(3)Si is governed by the Si content. The Cr content might impede the relocation of B from the interlayer into the base metal and the formation of CrB inside the ASZ is dominated by the Cr content. The high micro-hardness of the eutectic compounds is originated from the formation of boride matrixes such as Ni or Cr boride. The shear strength of the joint using BNi-9 after the completion of isothermal solidification is lower compared that that using BNi-3 and BNi-2, which could be related to the absence of Si in the filler metals constituent and the significant presence of Cr in BNi-9.展开更多
The effects of joining temperature(TJ)and time(tJ)on microstructure of the transient liquid phase(TLP)bonding of GTD-111 superalloy were investigated.The bonding process was applied using BNi-3 filler at temperatures ...The effects of joining temperature(TJ)and time(tJ)on microstructure of the transient liquid phase(TLP)bonding of GTD-111 superalloy were investigated.The bonding process was applied using BNi-3 filler at temperatures of 1080,1120,and 1160℃ for isothermal solidification time of 195,135,and 90 min,respectively.Homogenization heat treatment was also applied to all of the joints.The results show that intermetallic and eutectic compounds such as Ni-rich borides,Ni−B−Si ternary compound and eutectic-γcontinuously are formed in the joint region during cooling.By increasing tJ,intermetallic phases are firstly reduced and eventually eliminated and isothermal solidification is completed as well.With the increase of the holding time at all of the three bonding temperatures,the thickness of the athermally solidified zone(ASZ)and the volume fraction of precipitates in the bonding area decrease and the width of the diffusion affected zone(DAZ)increases.Similar results are also obtained by increasing TJ from 1080 to 1160℃ at tJ=90 min.Furthermore,increasing the TJ from 1080 to 1160℃ leads to the faster elimination of intermetallic phases from the ASZ.However,these phases are again observed in the joint region at 1180℃.It is observed that by increasing the bonding temperature,the bonding width and the rate of dissolution of the base metal increase.Based on these results,increasing the homogenization time from 180 to 300 min leads to the elimination of boride precipitates in the DAZ and a high uniformity of the concentration of alloying elements in the joint region and the base metal.展开更多
基金Projects(51171152,50871088) supported by the National Natural Science Foundation of ChinaProject(20126102110048) supported by Doctoral Fund of Ministry of Education of China+2 种基金Project(SKLSP201202) supported by Foundation of State Key Laboratory of Solidification,ChinaProject(2012JC2-02) supported by Natural Science Basic Research Plan in Shaanxi Province,ChinaProject (JC201268) supported by the NPU Foundation for Fundamental Research,China
文摘Metastable liquid phase separation and rapid solidification in a metastable miscibility gap were investigated on the Cu60Co30Cr10 alloy by using the electromagnetic levitation and splat-quenching.It is found that the alloy generally has a microstructure consisting of a（Co,Cr）-rich phase embedded in a Cu-rich matrix,and the morphology and size of the（Co,Cr）-rich phase vary drastically with cooling rate.During the electromagnetic levitation solidification processing the cooling rate is lower,resulting in an obvious coalescence tendency of the（Co,Cr）-rich spheroids.The（Co,Cr）-rich phase shows dendrites and coarse spheroids at lower cooling rates.In the splat quenched samples the（Co,Cr）-rich phase spheres were refined significantly and no dendrites were observed.This is probably due to the higher cooling rate,undercooling and interface tension.
文摘In order to investigate the microstructure evolution and gain complete isothermal solidification time, transient liquid phase （TLP） bonding of IN-738LC superalloy was carried out using powdered AMS 4777 as the filler metal. The influence of gap size and bonding time on the joints was investigated. For example, complete isothermal solidification time for 40μm gap size was obtained as 45 min. In the case of lack of completion of isothermal solidification step, the remained molten interlayer cooled in the bonding zone under non-equilibrium condition andγ–γ′ eutectic phase formed in that area. The relationship between gap size and holding time was not linear. With the increase in gap size, eutectic phase width became thicker. In the diffusion affected zone, a much larger amount of alloying elements were observed reaching a peak. These peaks might be due to the formation of boride or silicide intermetallic. With the increase in gap size, the time required for bonding will increase, so the alloying elements have more time for diffusion and distribution in farther areas. As a result, concentrations of alloying elements decreased slightly with the increase in the gap size. The present bi-phasic model did not properly predict the complete isothermal solidification time for IN-738LC-AMS 4777-IN-738LC TLP bonding system.
文摘An investigation was carried out to assess the applicability of transient liquid phase bonding of two dissimilar super-alloys with different interlayers. The effect of using three types of interlayer such as BNi-2, BNi-3, and BNi-9 on microstructure and mechanical properties was studied in the GTD-111/IN-718 system at 1100 ℃ for different bonding time. To determine the compositional changes and microstructure in the joint region, field emission scanning electron microscopy equipped with energy dispersive spectroscopy was utilized. The formation of Ni_(3)B in the athermally solidified zone(ASZ) is controlled by the B content and, accordingly, the morphology of Ni_(3)Si is governed by the Si content. The Cr content might impede the relocation of B from the interlayer into the base metal and the formation of CrB inside the ASZ is dominated by the Cr content. The high micro-hardness of the eutectic compounds is originated from the formation of boride matrixes such as Ni or Cr boride. The shear strength of the joint using BNi-9 after the completion of isothermal solidification is lower compared that that using BNi-3 and BNi-2, which could be related to the absence of Si in the filler metals constituent and the significant presence of Cr in BNi-9.
文摘The effects of joining temperature(TJ)and time(tJ)on microstructure of the transient liquid phase(TLP)bonding of GTD-111 superalloy were investigated.The bonding process was applied using BNi-3 filler at temperatures of 1080,1120,and 1160℃ for isothermal solidification time of 195,135,and 90 min,respectively.Homogenization heat treatment was also applied to all of the joints.The results show that intermetallic and eutectic compounds such as Ni-rich borides,Ni−B−Si ternary compound and eutectic-γcontinuously are formed in the joint region during cooling.By increasing tJ,intermetallic phases are firstly reduced and eventually eliminated and isothermal solidification is completed as well.With the increase of the holding time at all of the three bonding temperatures,the thickness of the athermally solidified zone(ASZ)and the volume fraction of precipitates in the bonding area decrease and the width of the diffusion affected zone(DAZ)increases.Similar results are also obtained by increasing TJ from 1080 to 1160℃ at tJ=90 min.Furthermore,increasing the TJ from 1080 to 1160℃ leads to the faster elimination of intermetallic phases from the ASZ.However,these phases are again observed in the joint region at 1180℃.It is observed that by increasing the bonding temperature,the bonding width and the rate of dissolution of the base metal increase.Based on these results,increasing the homogenization time from 180 to 300 min leads to the elimination of boride precipitates in the DAZ and a high uniformity of the concentration of alloying elements in the joint region and the base metal.
