| To reduce the melting temperature and improve the wearability,Cu-Sn-Ti active brazing filler metal was systematically studied by whole test with two factors and four levels,and optimized Sn and Ti elements of Cu-Sn-Ti brazing filler metal.The effect of In,Al,Ce and La on the microstructure and properties of Cu-Sn20-Ti15 brazing filler metal was studied by means of single factor test,the mechanism of In,Al,Ce and La elements in Cu-Sn20-Ti15 was revealed,and the optimal content of In,Al,Ce and La elements was obtained.The main conclusions are as follows:(1)Poor and variance analysis method is used for comprehensive experiment,the results show that Sn has a significant effect on the melting temperature and wettability,and Ti has a significant effect on the shear strength and microhardness.The optimal combination of Cu-Sn-Ti brazing filler metal is Cu-Sn20-Ti(10~15).With the increasing of Sn content,the evolution of microstructure of Cu-Snx-Ti10 is: ?-Cu solid solution + small amount of eutectic structure ? large amount of eutectic structure + ?-Cu solid solution ? eutectic structure ? large Cu Sn3Ti5 intermetallic compound + coarsening eutectic structure + Sn-rich ?-Cu solid solution.With the increasing of Ti content,the microstructure evolution of Cu-Sn20-Tix is: Sn-rich ?-Cu solid solution + large amount of Cu41Sn11 phase + strip Cu Sn3Ti5 phase + a small amount of rod-like eutectic structure ?Sn-rich ?-Cu solid solution + a small amount of Cu41Sn11 phase + large Cu Sn3Ti5 phase + a small amount of coarsed eutectic structure eutectic structure + bulk Cu Sn3Ti5 phase + small amount of Sn Ti3 phase ? Ti-rich ?-Cu solid solution + bulk Cu Sn3Ti5 phase + large amount of Sn Ti3 phase.With the increasing of Sn content,the melting temperature of Cu-Sn-Ti decreases and the wettability increases.With the increasing of Ti content,the shear strength of Cu-Sn-Ti increases first and then decreases,and the microhardness increases.(2)The microstructures of Cu-Sn20-Ti15-Inx are mainly composed of Cu Sn3Ti5 phase,eutectic structure and eutectoid structure.and the eutectic structure is mainly composed of Sn-Ti phase and ?-Cu phase,the eutectoid structure is mainly composed of In-Ti compound and ?-Cu phase.The existing forms of In element are eutectoid structure,?-Cu phase,Cu2 In Ti compound,and Cu4 In phase.The addition of In mainly causes the change of eutectic structure,eutectoid structure and the concentration of In in the ?-Cu phase.With the increase of In content,the eutectic structure is coarsened and its content decreased.The morphology changed from lamellar,rod-like to spherical and massive.The content of eutectoid structure increases and its phase is coarsened.The concentration of In in the ?-Cu phase increases with the formation of Cu4 In phase.In has a significant effect on the melting temperature,wettability and mechanical properties of Cu-Sn20-Ti15-Inx as cast brazing filler metal.When the In content is 1.47 wt%,the cast brazing filler metal has the lowest solidus temperature,the liquidus temperature,and the minimum solid-liquid phase temperature range.The brazing filler metal has the best wettability on the graphite surface.The shear strength and microhardness of as-cast brazing filler metal are the largest,and their values are 313.12 MPa and 378.44 HV0.5 respectively.Cu-Sn20-Ti15-In1.47 brazing filler metal can achieve good metallurgical bonding of graphite/steel.A continuous black Ti C layer is formed in the graphite/brazing seam interface area,and a large number of blocks or strips Sn-Ti compound vertically grows along the Ti C layer.In the brazed joint,In is dissolved in the Cu3 Sn phase and a-Cu phase,and no In formed compound is founded.It can be inferred that the mechanical properties of the brazing seam will not be deteriorated.(3)The microstructures of Cu-Sn20-Ti15-Alx are mainly composed of ?-Cu phase,bulk Cu Sn3Ti5 phase,eutectic structure and gray-black structure(Ti3.3Al3,Ti11 Al,Cu3Ti).Al is in the form of ?-Cu phase,Ti3.3Al3 phase and Ti11 Al phase.With the increase of Al content,the eutectic structure is coarsened and the proportion of gray black structure increases,and the concentration of Al in the ?-Cu phase increases.When the content of Al is 0.51 wt%,Cu-Sn20-Ti15-Alx has the lowest solidus temperature,liquidus temperature and the best wettability.The brazing filler metal has a high shear strength(244.58 MPa)and a larger microhardness(331.75 HV0.5).Cu-Sn20-Ti15-Al0.51 can achieve a good metallurgical combination of graphite/steel.In the brazed joint,Al dissolved in the ?-Cu phase,Fe2 Ti phase,and forms a small amount of Al-Fe compounds and Ti3.3Al phase.(4)The microstructure of Cu-Sn20-Ti15-Cex is mainly composed of ?-Cu phase,bulk Cu Sn3Ti5 phase,eutectic structure and Ce3Cu4Sn4 phase.Ce is dissolved in ?-Cu phase,and forms Ce3Cu4Sn4 phase and Ce Cu6 intermetallic compound.With the increase of Ce content,the Ce3Cu4Sn4 phase is coarsened and the content increases.When Ce reaches 5%,a new rod-like Ce Cu6 phase is produced.The content of eutectic structure decreases,and its morphology is changed from lamellar to the rod-like,spherical evolution.The existing form of La in Cu-Sn20-Ti15-Lax is Cu9 La Sn4 and Cu La Sn metal compounds.With the increase of La content,the eutectic structure is coarsened,and its morphology is changed from lamellar to rod-like and spherical.The content of Cu9 La Sn4 and Cu La Sn metal compounds increases and the size increased.When Ce/La content is 1.01 wt%,Cu-Sn20-Ti15 brazing filler metal has the lowest melting temperature and the best wettability.Ce/La increases the microhardness of Cu-Sn20-Ti15 while significantly reducing the shear strength.(5)Cu-Sn20-Ti15-Ce/Lax can achieve a good metallurgical combination of graphite/steel.Ce and La play an important role in purifying and refining the brazing filler metal and brazing joint interface.Ce and La tend to be localized on the surface of liquid brazing filler metal,which reduces the surface tension of liquid brazing filler metal and improves wettability of filler metal to graphite.The formation of Ti C? Ce C2 and La C2 is the main reason for the metallurgical bonding of brazeing filler metal/graphite. |
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