High Specific Gravity Tungsten Alloy for Rare Earth Element Strengthened Armor Piercing Core

High specific gravity tungsten alloys are a kind of tungsten-based alloys, which are composed of Ni, Fe, Co, Cu, Mo, Cr and other elements. Their density is as high as 16.5-19.0g/cm³. They are also known as high density tungsten alloys.

High density tungsten alloy not only has high density, but also has a series of excellent properties: high strength, high hardness, good ductility, good machinability, low thermal expansion coefficient, high thermal conductivity, good oxidation and corrosion resistance, good weldability, etc. This kind of alloy has been widely used in the core material, balance weight element, inertia element and ray shield material of rod-type kinetic energy armour piercing projectile.

In view of the shortcomings of the existing technology, some experts have added rare earth elements to high-density tungsten alloys and improved the sintering technology, including the following processes:

(1)Preparation of composite tungsten powder: Blue tungsten oxide was mixed with lanthanum oxide or cerium oxide in proportion of 112.7-118.9 parts by weight: 0.05-2 parts for 6-18 hours; then the mixture was reduced in a 15-tube hydrogen reduction furnace.

(2)Mixture preparation: the composite tungsten powder was mixed with the bonding phase nickel and iron for 6-12 hours according to weight ratio, and then the mixed powder was passed through 80 mesh-140 mesh screen.

(3) Compression forming: the mixed powder is compacted to obtain semi-finished products.
The best pressing method is isostatic pressing. The mixed powder is packed into rubber sleeve and pressed in isostatic press. The pressing pressure is 140 MPa - 200 MPa and the holding time is 3 - minute.

(4)Sintering: The compact is loaded into molybdenum or corundum boat dishes, and the filler is alumina powder. The boat dishes are sintered in a hydrogen sintering furnace at 1450-1540 ℃. The boat boat speed is 5-10 mm/min, and the hydrogen flow rate is 4-8 m³/h.

(5)Argon heat treatment: the sintered tungsten alloy blanks were dehydrogenated in the heating furnace under the protection of argon. The temperature was 1100-1300 ℃ and the holding time was 1-8 hours.

(6)Deformation hardening: after dehydrogenation, tungsten alloy blanks are heated to 400-900 ℃, and hot extrusion or rotary forging deformation of 10-70% deformation is carried out on extrusion equipment or rotary forging equipment.

(7)Prestressing aging heat treatment: The deformed high density tungsten alloy material is prestressing aged for 1-24 hours at 400-900 ~℃.

It is found that lanthanum oxide and cerium oxide can inhibit the segregation of impurity elements at the grain boundary of tungsten alloy, purify the interface between tungsten particles and bonding phase, and disperse the rare earth oxide in the bonding phase, strengthen the bonding phase and prevent the crack generation and propagation during impact and shear. At the same time, due to reasonable composition and strict control of process parameters in each step, many problems such as density, structure and mechanical properties of high density tungsten alloys are solved, thus maintaining high plasticity and excellent comprehensive mechanical properties.

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