The iridium alloy is an alloy containing other components of iridium. Most of the iridium alloy is brittle and difficult to process, which limits its application. People use a small amount of tungsten or hafnium to improve the processing properties of iridium in production. Adding a small amount of aluminum, iron, thorium, etc. can improve its impact toughness. The iridium alloy made from this method has the high melting point and high-temperature strength and good thermal shock resistance, which is also compatible with graphite and plutonium dioxide (PuO2) at high temperature and selected as the fuel container material for aerospace and medical thermoelectric devices.
The car spark plug made of iridium alloy is high in strength and temperature, and fast response, so it can make the electrode much smaller than the ordinary spark plug. Several important iridium alloys and their applications are described below.
Iridium tungsten alloy
Of all the metal tungsten has the highest melting point (3380 ℃), the lowest vapor pressure and the highest tensile strength ( at 1650 ℃). The corrosion resistance of tungsten is very good, and most inorganic acids have little erosion to it. So the tungsten is an ideal material for making heavy metal alloys. Iridium itself has a high melting point, chemical stability and high-temperature resistance to corrosion. The wear-resistance, hardness, strength and heat resistance of iridium tungsten alloy have been further improved. It is these precious properties that make the iridium tungsten alloy an indispensable element in today’s high-tech crystal glass industry.
Iridium – rhodium alloy is the most important iridium alloy. It is a continuous solid solution (composition and symmetry invariant alloy). With the increase of rhodium content, its density and hardness decreased, the pressure processing performance improved, and the resistance to high-temperature oxidation increased. Iridium – rhodium alloy can be used as thermocouple material.
Iridium cerium alloy
The work function of iridium (electrons overcome the binding of nuclei, the minimum energy required to escape from the surface of the material) is 5.4 electron volts, and its thermal electron emission is poor. After adding rare earth elements, the output power of iridium can be reduced to 2.5 ~ 2.6 electron volts. For example, the iridium alloy has the high-temperature strength and high emissivity, which can obtain large emission current density with this alloy.
Iridium osmium alloy is a peritectic alloy with hard and brittle texture and extremely difficult to process. Osmium alloys containing 30% ~ 70% osmium (atomic fraction) are very good cathodic coating materials. Because of its hard alloy, it can also be used to make pen tips and pivot materials.
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