After Sintering Heat Treatment after cold deformation of Crystalline Cyclic Heat Treatment

Cyclic Heat Treatment

Cyclic heat treatment of the alloy properties also have a certain impact, mainly reflected in the W - Ni - alloy cyclic heat treatment can alter the uniform distribution of binding phase is conducive to penetrate phase sintering of tungsten - tungsten grain boundaries, reducing tungsten - tungsten distance. NohJoon-Wong, who studied tungsten -5.6 93 -1.4 iron-nickel cyclic heat treatment process, the sintered tungsten alloy in a nitrogen atmosphere at 1150 ℃ incubated for 1h, then water quenching, this process is repeated several times, the results show that with the increase in the number of cycles to infiltrate tungsten - tungsten grain boundary phase volume increased bonding, bonding phase can be more fully penetrate to WW grain boundaries.

Circulation of heat treatment on the tensile mechanical properties of the alloy of tungsten grain size related. When the tungsten grains from the 25μm to 100μm, although the use of cyclic heat treatment, the tensile strength and elongation still down, respectively, and 25% down from 920MPa to 740MPa and 11%, after a heat cycle, the impact absorbed energy from 50J dropped to 22. SJ. When W is the grain size is reduced to 25-35μm, the cycle of heat treatment on the absorbed energy increased significantly affected. Alloys from 57J impact energy up to 170J, impact specimen fracture morphology changed greatly from tungsten - tungsten interfacial fracture to the dimple-like ductile fracture binding phase change.

Deformation and Then Crystallized

Cold working such as extrusion, rolling, forging, etc., may increase the tensile strength, but the alloy has decreased ductility. Alloy microstructure by cold deformation of fibrous texture, this texture with penetrators axial orientation have a greater impact on the performance of the alloy, thus affecting its penetration performance. Goren et al cold deformation after crystallization was studied tungsten -7% 90% -3% Ni alloy after swaging (diameter shrinkage of 82%) and annealed at 1480 ℃ 40s obtained crystals uniformly round lOlμm tablets. And the greater the deformation, the shorter the annealing time. In the annealing process, the larger tungsten grains (30-50μm) first forming sub-grain boundaries, some of the molten adhesive through the sub-selective phase boundary, the last elongated tungsten grains are divided into smaller round tungsten grains, thereby significantly improving the microstructure of the alloy.




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