(The Investigation Of Phase Diagrams Of Sm-TM Systems And Sn Based Solder Systems)

The phase diagrams of Sm-TM systems and Sn based solder systems have been investigated using experimental methods and calculation.Co-Sm system is a basic subsystem of the rare-earth permanent magnets Sm(Co,Cu,Fe,Zr)x. The experimental difficulties of high volatility, high activity and easy-oxidization of Sm-rich alloy have been resolved as alloys sealed in Ta crucible for the induction melting and DSC analysis. Combing microscope analysis and differential scanning calorimetry (DSC) analysis with slow scanning rates as1℃/min and0.5℃/min, the phase diagram of Co-Sm system in Sm-rich side has been modified. The phase denoted as Sm9Co4in literatures has been revised as Sm5Co2according to its crystal structure. Five invariant reactions and the liquidus have been determined and the relations between three types of Sm allotropies and Sm3Co phase have been well demonstrated.Co-Sm system has been re-assessed using global optimization. The errors existed in literature have been revised by using a proper model for the calculation of magnetic energy and strictly controlling the parameters to avoid the unreal state as having miscibility gap of liquid at high temperature or decomposition of phases at low temperature. The Sm2Co17and SmCo5have been modeled as (Co)0.833333(Sm)0.111111(Co2,Sm)0.055556and (Co,Va)0.833333(Co2,Sm)0.166667, respectively, which are coincident with their crystal structures and the sites'occupations of atoms. The calculated composition ranges are coincident with the experimental data. The calculated phase diagram agreed very well with the experimental phase diagram, which are important for the design of permanent magnets.Ni-Sm alloy is a promising material as an excellent hydrogen storage material. The phase diagram of Ni-Sm system at Sm-rich side has been modified using DSC analysis with quite slow scanning rates as0.3℃/min and0.1℃/min, heat-treatment in situ during DSC process for equilibrium transformation, and microscope analysis of various equilibrium structures and solid structures. Two new phases Sm7Ni3and Sm3Ni2have been found and their stable ranges have been determined. Seven invariant reactions have been determined including the reactions'temperature and phases'information. The thermal effects from the reactions with quite close temperatures (close to2℃) have been well separated and demonstrated. The experimental method used in this investigation is helpful for the verification and revision of phase diagrams of other systems, especially for the RE-TM system.The Ni-Sm system has been re-assessed. The calculated results agreed very well with the experimental results.The investigation of Sn-based lead-free systems, including Cu-Sb-Sn and Ni-Sn-Zn systems, are a part of COST MP0602project for the investigation of high temperature lead-free solders.The isopleth of Cu-Sb-Sn system as Sn/Sb=1:1have been determined combing DSC analysis and microscope analysis on annealed alloys. Three invariant reactions and related liquidus have been determined. The solubility of Sn in p(Cu2Sb) and Sb in ε(Cu3Sn) and η(Cu6Sn5) have been determined. The peaks from un-equilibrium reactions shown on the DSC curves have been revised according the equilibrium phases presented in the annealed alloys. The reactions'scheme has been represented using preliminary extrapolation and calculation. The construction of this isopleth is important for the construction of phase diagram of Cu-Sb-Sn system and the design of the related solder and the welding process.The interfacial reactions between SnxZn1-x liquid and Ni substrate have been investigated with changing of Zn content, the annealing time and the annealing temperature, where the corresponding diffusion layers, the diffusion paths and the phase formation sequences have been determined. The experimental difficulties of high volatility, high activity and easy-oxidization of Zn-rich alloys have been resolved and the isothermal section at600℃has been well-constructed by structure analysis on annealed equilibrium alloys. Six ternary phases have been found, including three new phases. The composition ranges of phases have been determined, as well as their relationship. The isothermal section, including seventeen triangles, at600℃have been determined. This work is critical for the construction of Ni-Sn-Zn phase diagram.