Study On Densification And Properties Of Tantalum Tungsten Alloy Of Spark Plasma Sintering

Tantalum tungsten alloy has a series of excellent properties,such as room temperature workability,corrosion resistance,super temperature resistance and low vaporization rate at low vapor pressure and high temperature.It is widely used in major engineering fields,such as electronic engineering,aerospace engineering,weapon system engineering and so on.Through the traditional electronic smelting technology,the tantalum tungsten alloy has large grain size and obvious anisotropy due to rolling.Therefore,this paper used a high-performance tantalum tungsten alloy manufacturing technology,which combined with mechanical alloying and discharge plasma sintering technology.It had been studied about the densification mechanism,microstructure evolution behavior and the influence of process parameters on the mechanical properties of tantalum and tantalum tungsten alloy manufacturing by spark plasma sintering.Some achievements are obtained.During the process of discharge plasma sintering,the rapid densification temperature range of pure tantalum was 800-1300 ?,and the maximum shrinkage rate of the sample was 1100 ?.When the sintering temperature increased from 1500 ? to 1900 ?,the density and the grain size were increased gradually.At the same time,the tensile strength and flexural strength increased,and the micro-hardness increased first and then decreased.The fracture mode of samples was transformed from brittle fracture to ductile fracture.During the sintering process,the apparent activation energy of pure Ta sintering is 107.01KJ/mol for low temperature/low effective stress exponent n=1.6.The densification mechanism is a series of interfacial reaction and grain boundary diffusion of grain boundary sliding linkage;For the high temperature/high effective stress exponent n=3.1,the densification mechanism is dislocation climbing,its dislocation source density is related to the effective stress.When the effective stress exponent was equal to 4.1,the densification mechanism was still dislocation climbs,but dislocation source density was independent of the effective stress.In the condition of axial pressure 35 Mpa and vacuum degree less than 10 Pa,the temperature raised from room temperature to 700 ? with 100?/min heating rate,preservation 5min,and then heat up to 1200 ?,preservation 5min again,and then heat up to 1600 ?,soak 5min again and cooled to room temperature in the furnace finally.Pure tantalum exhibited excellent ductility at room temperature.The tensile strength of tantalum was 325.3 Mpa,and the bending strength was 338.83 Mpa.The pure tantalum exhibited excellent ductility at room temperature,which the tensile strength of tantalum was 325.3 Mpa and the bending strength was 338.83 Mpa.The mixed powders with Ta-2.5wt%W,Ta-5wt%W,Ta-7.5wt%W and Ta-10wt%W components can be alloyed at sintering temperature 1600 ?,which formed tantalum tungsten solid solution with density more than 94.3%.With the increasing of tungsten content,the alloy density and grain size decrease,the micro-hardness and alloy strength increased and the plasticity decreased.The brittleness of Ta-10wt%W alloy increased,its tensile strength was 693.41 Mpa and the bending strength was 749.25 Mpa.The effect of mechanical alloying parameters on the Ta-10wt%W composite powder was comprehensively analyzed,and the optimized parameters for pre-alloyed powder preparation were obtained.Mechanical alloying can improve the powder sinterability,grain refinement and alloy mechanical properties.The alloy sintered density can reach up to 98.5%,the ultimate compressive strength can reach 2239 Mpa at room temperature,while its tensile strength was 214 Mpa at 1000?.