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The paper examines the sintering kinetics of porous strips based on binary mixtures of ultrafine nickel, copper, and cobalt powders at 400-800ºC under 5-20 MPa for 5-30 min. Concentration and kinetic dependences of shrinkage on sintering parameters are analyzed.Commercial powder materials, including copper and nickel, with particulate sizes ranging from 40 to 100 μm are used in the diffusion welding of steels and alloys [1,2]. The ultrafine nickel powder with particles smaller than 0.1 μm was first used in combining soft and hard magnetic materials [3]. This made it possible to make a uniform-strength weld at lower welding temperature (T w ≥ 550°C) and to eliminate plastic deformation of parts.The initial electrophysical properties of magnetic materials remained as they were [4]. The use of binary powder mixtures as intermediate layers can further decrease the temperature of diffusion welding to extend the range of welding materials (e.g., piezomaterials) and stabilize the magnetic and electrical parameters of parts.The objective of this paper is to study the sintering kinetics of binary mixtures of ultrafine nickel + copper, nickel + cobalt, and copper + cobalt powders for their use for solid-phase combination of materials to extend the range of steels and alloys welded.Binary nickel-copper and nickel-cobalt powder mixtures are systems with complete miscibility and copper-cobalt mixtures with partial miscibility [5]. A single phase--a solid solution of the components--forms during sintering in the former system. When the latter system is sintered, either one phase (over the range of complete miscibility) or two phases (a saturated solid solution and excess phase of the other component) form depending on the concentration.The kinetics of pressure sintering was studied using porous rolled strips with the following characteristics: initial thickness 65 μm; porosity 55%; initial particle size (base fraction) ≤0.1 μm; specific surface area from 17 to

The thermal decomposition of metal formates in the production of ultrafine metal powders permits controlling particle size and specific surface S sp , i.e., controlling free surface energy [1,2]. It is believed [3] that the smaller the particles and the more developed the surface, the more nonequilibrium their state and the higher their activity in subsequent pressing and sintering. In turn, this activity reveals itself when thermal and mechanical loads on these powders are low.This paper examines how the process of producing double formate mixtures and thermal decomposition modes affect the composition, particle size, and physical and chemical properties of ultrafine powders.Two methods were employed to produce double powder mixtures (nickel + copper, nickel + cobalt, copper + cobalt) containing components in different ratios, %: 10 + 90, 25 + 75, 50 + 50, 75 + 25, and 90 + 10. The first method involved obtaining pure metal formates, their careful mechanical mixing until they are uniform, and thermal decomposition. The second method involved obtaining formates in the form of solid solutions (or formate of a mixture) with a needed ratio of components, and their thermal decomposition [2].The production of pure metal formates and solid-solution formates is based on the precipitation of basic carbonates or hydroxides of these metals, their subsequent dissolution in the equimolecular amount of formic acid, and sedimentation of practically insoluble formates from the oversaturated solutions. Nickel and cobalt nitrates and copper sulfate are starting compounds for obtaining pure metal formates. Excess sodium carbonate is added to the solution of appropriate salts at 50-60ºC and vigorously mixed to precipitate basic metal carbonates according to the following reactions: 2Ni