Physical properties are an important way of distinguishing one material from another. In the study and application of metallurgy, physical properties are often considered a broader category than mechanical properties, but not all properties overlap. Physical properties are most easily distinguished from mechanical properties by the method of testing. While mechanical properties require forces to be applied to obtain a measurement, physical properties can be measured without changing the material.
That said, physical properties do change in different environments. For example, most metals have a higher density at lower temperatures due to the principles of thermal expansion and contraction. Color and appearance, which are also physical properties, change based on a number of environmental factors.
To learn more about mechanical properties of metals, check out our blog post here.
The word alloy appears throughout the Eagle Group Blog, especially here in this series. An alloy is a uniform mixture made from a combination of individual elements, when at least one of the elements is a metal. Common alloys include bronze, which is a mixture of copper (Cu) and tin (Sn). Steel is a mixture of iron (Fe) and carbon (C), and stainless steel includes other alloying agents like chromium (Cr), nickel (Ni) and manganese (Mn).
Corrosion resistance, on the other hand, is the material's ability to resist the reaction to move toward a more stable state in its environment.
Raw aluminum, silicon, titanium and their alloys are naturally corrosion resistant due to an unreactive layer that quickly forms on their surfaces. A common alloy for many applications requiring corrosion resistance is stainless steel. Unlike carbon steel, stainless steel alloys are able to resist surface corrosion when exposed to environments that would normally cause corrosion, including wet, acidic or high heat.
Click here read our "Corrosion Resistance" blog post
Alloys more commonly used in manufacturing have lower densities. Steel averages around 494 lbs./ cubic foot, while stainless steel is a bit less. Titanium is about half the density of steel, and aluminum is about one-third. Practically speaking, this means that a part made of steel will weigh approximately three times more than the exact same part made of aluminum. However, steel has other advantages like hardness and strength, and so lower volumes or thicknesses of material can provide the same or better performance, comparatively.
Eagle Alloy and Eagle Precision often produce complex, thin-walled castings from different carbon and stainless steel alloys. The alloy affects the design, production process and finishing techniques used to manufacture each cast part.
Melting point is an important consideration for metal manufacturers. Many casting facilities utilize sand casting methods like airset or shell mold casting because the non-metal molds can withstand higher temperatures required to melt steel. Aluminum, on the other hand, can be cast using reusable steel molds, since it has a much lower melting point than steel.
Iron is one of the most magnetic metals, and so ferrous metals (metals containing iron) like steel also exhibit degrees of magnetism--specifically ferromagnetism.
While the above properties are by no means exhaustive, they do represent many of the most important properties involved in choosing a material for metalcasting or CNC machining. At the Eagle Group, our metallurgy experts have the experience to evaluate a product's needs and based on customer input, ultimately suggest the optimal alloy for the job. We also employ an exhaustive APQP process for all new projects, which allows us to dial in exact parameters throughout the manufacturing process that lead to the best quality casting.