Frequently Asked Questions About Tungsten Heavy Alloys
Q: Are all tungsten alloys inherently brittle?
A: No. This misunderstanding comes largely from experiences with pure tungsten in the recrystallized state. Tungsten heavy alloy has a totally different, rounded grain structure that provides good machining behavior and the ability for some alloys to be stretched by 30% of their initial length without fracture.
Q: Is tungsten one of those rare metals that could be in short supply?
A: While the element tungsten isn't as well known as other commercial metals, its geological abundance is roughly that of copper or tin. This means tungsten will be available for new and existing applications for a long time to come.
Q: Is tungsten heavy alloy similar to tungsten carbide?
A: While both families of materials are made by the powder metallurgy process of liquid phase sintering and both are very rigid, many differences exist. Tungsten carbide provides high hardness and wear resistance. Tungsten heavy alloy offers both ductility and higher density. The two families are not interchangeable.
Q: Why is depleted uranium (DU) being replaced by tungsten alloys in many applications?
A: Tungsten heavy alloys provide high material densities comparable to DU without the inherent radioactivity, toxicity, and high chemical reactivity of the latter. This simplifies life cycle considerations for many components.
Q: Can tungsten heavy alloy be cast like most metals?
A: No. Due to the extremely high melting point of tungsten, it is not feasible to melt and cast alloys containing the high percentages of tungsten needed to achieve the density range of interest. Rather, energy and material conservative powder metallurgy techniques are used to produce fully dense metal shapes.
Q: Why is tungsten so much more expensive than lead?
A: The significantly higher cost of tungsten results from the higher cost of the mined ore as well as the more complicated processing needed to get to the metallic state. While it costs more, tungsten provides a number of benefits versus lead, including both material performance and environmental factors.
Q: Is solid state sintered tungsten heavy alloy available?
A: Yes. While providing excellent dimensional control, stopping the sintering short of a full liquid-phase sintered state severely compromises the mechanical properties otherwise attainable in a given part. Due to the lower ultimate strength and greatly reduced ductility, such a sintered state should be avoided.
Q: Is it possible to enhance the mechanical properties of sintered heavy alloy?
A: Yes. Post-sinter processing is available to increase the ductility and toughness of tungsten heavy alloys. This should be strongly considered for mechanically demanding applications where "bend before break" behavior is a must.
Q: What are "non-magnetic" tungsten heavy alloys?
A: This term incorrectly implies that standard heavy alloys exert some sort of significant magnetic field, which they do not. Rather, this term denotes alloys that offer very low magnetic permeability due to their chemical composition. Such alloys are commonly used for radiation shielding in close proximity to electron optics or geomagnetic devices.