When selecting materials for engineering purposes, many factors must be considered. Manufacturers understand that every metal alloy has unique properties that react to mechanical and chemical processes in specific ways. In order to maximize the efficiency and cost savings of any job, understanding these properties and deciding which particular alloy is best suited for the task at hand is of primary importance.
The mechanical properties of metal are generally determined by a number of factors, including grain size, heat treatment, atmospherics exposure, and temperature. Together, these attributes affect how a metal reacts to the forces it is exposed to in industrial processes. Manufacturers must carefully test alloys in order to know how they will be affected and what conditions will push them to the breaking point.
Different processes affect metals in different ways. One important concept is that of stress and strain. When comparing specimens of various sizes, it is first necessary to calculate the load per unit area, also known as the normalization to the area. Stress is formulated dividing the force by the area. When conducting tension and compression tests, the area of relevance is perpendicular to the force. On the other hand, for shear or torsion tests, the area of relevance is perpendicular to the axis of rotation.
Stress and strain can cause metal alloys to react in undesirable ways and must be tested carefully. Elastic deformation describes a situation in which after the stress is removed, the material is able to return to its previous dimensions. The elasticity indicates its ability to remain stable under stress, and that the deformation is reversible and non-permanent. In contrast, plastic deformation means that after the stress is lifted, the metal is unable to return to its prior shape. Instead, the stress has caused permanent, irreversible deformation.
The factors that affect the mechanical properties of metal are varied. For instance, yield strength, hardness, the ductile-brittle transition temperature, and susceptibility to environmental conditions are all affected and can be improved, by altering the grain size.
Metals, including aluminum, are composed of crystals, which are also referred to as grains. Aluminum with a small grain size is referred to as fine-grained, while aluminum with relatively large grains is known as coarse-grained. Aluminum alloys with fine grains normally retain greater tensile strength and greater fatigue strength. Such alloys can more easily be work hardened. Aluminum with coarser grains has more surface roughness and is more difficult to polish.
Other effects of grain include the fact that coarse-grained aluminum is not as tough and therefore is more likely to suffer permanent distortion under stress. However, coarse-grained aluminum has advantages when it comes to workability, hardenability, and forgeability. They also react to temperatures differently. At room temperature, fine-grained aluminum is stronger and harder, but at higher temperatures, coarse-grained aluminum has better creep resistance. In general, a simple formula can determine the relationship: the strength of a metal is inversely proportional to the square root of the grain size.
Temperature is another factor that affects mechanical properties of a metal, including the tenacity and elastic limit. Heat treatment is an important step in many industrial processes, as it can greatly improve the mechanical properties of aluminum and other metals, such as ductility hardness, tensile strength, toughness, and shock resistance.
There are numerous benefits to heat treatment when it comes to aluminum alloys. It can refine the grain and improve machinability. Working metal induces internal stress whether at hot or cold temperatures, and heat treatment is one way of alleviating that stress. Additional benefits include a modified grain structure and improved corrosion resistance, and more desirable chemical, magnetic, electrical, and thermal properties.
Atmospheric corrosion is a significant problem for metals and needs to be a key consideration for manufacturers. Most metals become oxidized when exposed to the atmosphere for extended periods of time. This oxidation of the metal surface creates a film, and is especially prevalent in the presence of moisture, sulfur dioxide, and hydrogen sulfide, and decreases electrical resistivity of the material.
The atmospheric effect depends on a number of factors, including the characteristics of the metal, the quality of the protective surface film, the presence of certain agents that can reduce any corrosive effects, and the presence of surface cracks or discontinuities. Once again, selecting the right aluminum alloy depends on knowing what environmental conditions it will be exposed to over the course of its product life.
Low and high temperatures will affect aluminum alloys in different ways, depending on the mechanical properties. For low temperatures, in general, a decrease in temperature means there will be an increase in tensile and yield strength. Aluminum alloys, as well as nickel and copper, will retain most of their toughness and ductility at low temperatures. For extremely low temperatures, less than -100 degrees Celsius, non-ferrous metals retain their properties better than ferrous metals. Low temperature can also lead to the stabilization of low thermal vibrations and lattice parameters.
At high temperatures, on the other hand, field stress and tensile strength decrease as the temperature increases, as will stiffness and fracture stress. High temperatures especially affect steel, and its toughness will be reduced. This is because as the temperature rises, there is a correlated increase in the thermal vibration of atoms, which causes changes in the structural properties of the metal. Many aluminum alloys, meanwhile, will retain their mechanical properties at high temperatures.
Aluminum has many mechanical properties that make it desirable for industrial processes. It is lightweight compared to steel, copper, and brass, and has excellent corrosion resistance to various environmental conditions. It offers high reflectivity, making it a great choice for decorative applications. And despite a lower density, many aluminum alloys can actually exceed the strength of steel. It keeps its toughness at low temperatures and is an excellent conductor of heat and electricity, making it a great choice for electronic applications. When compared at equal weights, aluminum conductivity is 204% that of copper. It is easily polished and offers greater machinability. And it is non-toxic, meaning it can be used for many food and beverage applications. On top of all that, aluminum is also easy to recycle.
Aluminum alloys are a durable, adaptable, and high-quality option for your manufacturing needs. Clinton Aluminum follows a philosophy of “The Right Alloy for the Right Application” and we take pride in being a technical resource partner to our suppliers and customers.