Tungsten Copper and Molybdenum Copper are pseudo-alloys made of high melting point tungsten, molybdenum, and high conductivity copper by powder metallurgy process. Tungsten Copper and Molybdenum Copper properties include excellent electrical and thermal conductivity, high strength, and corrosion resistance. At present, they are mainly used as an electrical contact material in electrical switches, lead frames and heat sink materials of integrated circuits, etc.
Measurements to Tungsten, Molybdenum, and Copper Powder
Tungsten powder, molybdenum powder, 200 mesh copper powder, and auxiliary materials with an average particle size of 2 ~ 6 μm were uniformly mixed and pressed in a 10X10 mm steel die and sintered in high-temperature sintering furnace at 1330 ~ 1350 ℃. Then the tissue was observed under Neophot-II metallographic microscope. The 7501 eddy current conductivity meter measures the conductivity. The pycnometer on an analytical balance with an accuracy of 0.1 mg measures the density. HB-3000 Brinell hardness tester carries on the hardness measurement. A self-made instrument measures thermal conductivity.
Microstructure of Tungsten Copper and Molybdenum Copper
Figs. 1 and 2 are Tungsten Copper and Molybdenum Copper microstructure photos. We can see that Tungsten Copper and Molybdenum Copper microstructure distributions are the same. The sintering temperature is higher than the copper melting point. Molten copper uniformly distributes on the structure of tungsten or molybdenum. Molybdenum particles tend to grow, as the figure shows. That may be related to the more manageable growth of Mo grains when holding temperature at higher sintering temperature.
Table 1 Molybdenum Copper properties and Tungsten Copper properties
Table 1 lists the related tungsten copper and molybdenum copper properties. The tungsten copper hardness and density are higher than those of molybdenum copper materials. The molybdenum copper electrical conductivity materials are higher. The tungsten copper thermal conductivity is higher. In addition, with the increase of copper content, the hardness and density of the same material decrease whiling the electrical conductivity and thermal conductivity increase.
The molybdenum copper and tungsten copper metallograph are basically the same. This is due to the fact that they are prepared by the mixed powder melting sintering method. The crystal structure and atomic radius of W and Mo are almost the same. The temperature difference between the melting point of molybdenum and the sintering temperature (TMo melting point-T sintering) is smaller than the temperature difference between the melting point and the sintering temperature of tungsten at the same sintering temperature. It makes molybdenum grain grow more obviously than tungsten grain (W grain actually grows) after long-term heat preservation. As for the great difference between tungsten copper properties and molybdenum copper properties, it is determined by their basic physical properties (see Table 2)
Table 2 Physical Properties of W, Mo and Cu Elements
N–Effective number of electrons per unit volume
T-thermodynamic temperature (K)
π, k, m-constant
The data in Table 3 and formulas (1) and (2) conclude that the conductivity of molybdenum copper material is greater than that of tungsten copper material. Tungsten copper thermal conductivity is greater than molybdenum copper material. It tends to increase with the increase of copper content. According to the above analysis, molybdenum copper alloy is suitable for high-temperature-resistant materials or electrical contact materials in various instruments, electronic devices, and aviation. That is because of its low density and better electrical conductivity than tungsten copper. Mainly it may become the first choice material to replace pure W, Mo, SiO2, and Al2O3 in large-scale integrated circuits. Molybdenum copper alloy is suitable for high voltage contact material heat sink material, high specific gravity alloy electrode material, and unique military material because of its better high-temperature performance, good thermal conductivity, high density, and high hardness.
Physical Properties of Tungsten, Molybdenum, and Copper Elements
Tungsten copper hardness and density are higher than that of molybdenum copper because tungsten hardness and density are nearly twice as high as molybdenum hardness and density. Powder metallurgy pseudo-alloy properties depend more on the composition of constituent elements; The molybdenum copper electrical conductivity is higher than tungsten copper and tungsten copper thermal conductivity is higher than molybdenum copper. This is mainly due to the atom’s properties and the binding force of electrons (see Table 3).
Table 3 Electronic Properties of W, Mo, and copper Elements