Processing of iron-titanium powder mixtures by transient liquid phase sintering

2006

Metall Mater Trans A

A simple model was developed to predict the impact that solid-state interdiffusion and dissolution have on liquid formation and its duration during transient liquid phase sintering (TLPS). The model predicts that solid-state interdiffusion can dramatically reduce the amount of liquid initially formed during heating. This reduction is dependent on the heating rate and initial base metal particle size. In cases of sintering above the additive phase melting point, the model predicts that base metal dissolution increases liquid phase formation and that this additional melting reduces the base metal particle size. The model predicts that longer times are required to solidify isothermally the greater amounts of liquid formed at higher temperatures (because of dissolution). This agreed qualitatively with experimental results for a Ni-65 wt pct Cu TLPS mixture sintered at 1090°C and 1140°C. Quantitative comparisons between the model and experiment were good at 1140°C; however, the rate of isothermal solidification was underestimated by the model for intermediate sintering times at 1085°C.

Section: Introductionmentioning

confidence: 99%

Modelling the influences of solid-state interdiffusion and dissolution on transient liquid phase sintering kinetics in a binary isomorphous system

Turriff

2006

Metall Mater Trans A

“…S Pb ϭ C Pb W Pb and average compositions of Sn (in weight percent in the Pb and eutectic, respectively, at a particular time, t. Therefore, Eq. S E ϭ C E W E , where W Pb and W E are the weight fractions of each phase within the mixture, and C Pb and C E are the [1] can be re-expressed as…”

Section: Analysis and Discussionmentioning

confidence: 99%

“…When this mixture is heated, 30 pct of its use of less expensive elemental powders vs alloyed powders, volume (the volume fraction of the eutectic powder) will and reduced microstructural coarsening. [1] Despite its imporbecome liquid at 183 ЊC (i.e., assuming no interdiffusion tance as an advanced powder processing method, a fundabetween the powders in the solid state (stage I of Figure mental understanding of the process, and the important 1)). If the mixture is held at this temperature, the liquid will variables controlling it, is incomplete.…”

Section: Introductionmentioning

confidence: 99%

“…tions are most importantly determined by the choice of mateThis alloy represents a model system for several reasons rials, but also the processing variables including powder size, including the following: (1) it has simple binary eutectic green powder packing density, heating rate, and sintering phase diagrams; (2) its diffusivity and solidification behavior temperature. [1][2][3][4][5][6][7][8] The importance of the time the transient are well known; [11][12][13][14] (3) it represents a near-ideal TLPS liquid is present is widely acknowledged. [2,5] However, the system as defined in References 2, 3, and 8; (4) the pure resolidification kinetics of the transient liquid is not well metal and eutectic powders with spherical shape are readily understood.…”

Section: Introductionmentioning

confidence: 99%

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Thermal analysis of isothermal solidification kinetics duirng transient liquid-phase sintering

Lucier²

2001

Metall Mater Trans A

A technique for experimentally measuring the kinetics of isothermal solidification during transient liquid-phase sintering (TLPS) has been successfully developed using differential scanning calorimetry (DSC). Comparison of these data with a model based on diffusion of Sn solute into an array of spherical Pb particles reveals very good agreement between predicted and measured solidification rates. The DSC technique and the solid-state diffusion model represent valuable tools in investigating the parameters that control TLPS, such as powder size, solder composition, process temperature, and heating rate.

“…6,7,[10][11][12][13] However, the primary objective of current investigations to develop a VMP effect distinguishes it from conventional TLP sintering. For example, TLP sintering is primarily a solid-state process where only a small volume fraction (i.e., ϳ1-5 vol.%) of liquid is used to aid in sintering.…”

Section: Introductionmentioning

confidence: 95%

High-temperature variable melting point Sn-Sb lead-free solder pastes using transient liquid-phase powder processing

2005

Journal of Elec Materi

During this investigation, a high-temperature, variable melting point (VMP) Sn-Sb solder paste was developed. The solder was created by mixing pure Sn and Sb powders together with a flux to form a paste. The proper choice of flux composition and Sn powder size resulted in a Sn-10wt.%Sb solder paste that had an initial melting point of 232°C and solder ball formation at peak temperatures as low as 241°C. This represents a significant reduction in the process temperature that would normally be required for a prealloyed solder with a melting point of 250°C. When this solder paste is reheated, significant remelting does not take place until a temperature above 241°C is reached. In this way, the solder exhibits a VMP. Experiments indicate that this VMP behavior is due to isothermal solidification (or freezing) at the solder temperature owing to the partial transient liquid-phase (TLP) behavior of the solder powder paste.