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Molybdenum tungsten alloy

Mo - W alloy with 25% tungsten alloy melting point increased about 200 ℃. So it is important significance of this series of alloys. As everyone knows Mo - W system is a continuous solid solution; character constants and density alloy is a linear function of its chemical components; electrical resistivity of 50Mo - 50W alloy has the minimal value.

In order to determine the effect of tungsten on molybdenum heat resistant strength, the tungsten content from 2.5% to 50% of the molybdenum alloy. Vacuum arc melting alloy was 80mm and 100mm for the crystallizer diameter, carbon, zirconium, titanium as the oxidizing agent. Ingot in hydrogen furnace heating at 1700 ~ l after 900 ℃, thermal deformation under 750 kg hammer. Get 40 mm diameter rods or thin slab with free forging method. Cutting, bar to continue forging, or rolled round bar diameter 16mm, slab rolling into sheet with thickness of 1 ~ 2mm.

To add no more than 10% of the molybdenum tungsten, ingot melting and thermal deformation of metal behavior does not have what effect. In tungsten containing 20%, 20% or more of the alloy ingot, found that the grain refinement, while forging plastic deformation resistance increased. When the tungsten content is 30%, very difficult alloy free forging deformation, even when the deformation temperature up to 1900 ℃, forgings are often cracks. 50Mo - 50W alloy can not actually by free forging.

According to the characteristics of extrusion process of Mo-W alloy, tungsten content greater than 20% by extrusion deformation is reasonable. Higher mechanical properties at room temperature and 1200 ℃ is less than 20% of the content of tungsten alloy than. Therefore, from a series of Mo-W alloy for Mo-20W, Mo-30w and Mo-50W alloy.

The room temperature strength increased with the increase of tungsten content increasing, at 400 ℃, especially in L at 200 ℃, the strength of 50Mo-50W alloy composition close to the highest. At this time, molybdenum, tungsten, tungsten and intensity than the alloy. At the same time, in 1800 ℃, with the increase of the strength of the alloy of tungsten in alloy is monotone increasing. This is logical, because at the temperature of 0.6---0.8%, Mo solid solution strengthening lattice structure factors at play [in component 50%. Mo (mole fraction), 50%W (mole fraction) case, the lattice distortion caused by alloy elements atomic reaches maximum value. At higher temperature, bonding force plays a role in determining the lattice. If the relation between strength and temperature in the coordinate bonding force, then sigma. / γ = f (T/T point) of the curve is very close to each other. In the temperature range of 0.5 ~ 0.7 T melting points, that is the largest regional organizations in the sensitivity, the difference between the maximum curve.

Therefore, molybdenum alloy of tungsten content ≥ 20% has obvious superiority in heat intensity, but also in the 500 ~ 1500 ℃, alloy composition close to 50Mo-50W resistant strength is the highest, when the temperature is higher than 1500 ~ 1700 ℃, the tungsten content of alloy is high, heat resistant strength of the alloy is also higher.