Metals or elements have almost no use in pure form. Instead, every metal gets intentionally mixed with other elements or metals. Thus, the composition becomes an alloy, being suitable for everyday utility.
The mixing elements effectively alter all the properties of a base metal/element. Even slight changes in contents significantly influence the properties. So, it’s a must to know these elements and their roles.
This module briefly discusses the common alloying metals as well as the harmful ones with their effects.
What are Alloying Elements?
Alloying metals are the elements added to a base metal in controlled quantities to change, alter, or transform the desired properties. Only a few special exceptions aren’t necessarily elemental or metals.
The resulting mix-up of elements becomes an alloy of the base metal. Altering the quantity of one or more metals effectively makes another alloy. That’s why there are hundreds of alloys of one metal alone.
Alloying elements are also called impurities or accompanying elements. However, impurity mostly suits the unwanted presence of certain elements. And they cover a negligible portion of a full composition.
Common Chemical Elements in Alloys
There are several elements to impart desirable properties in a metal alloy. An element can be base for itself whereas the same metal can act as an alloying element. Aluminum alloys have Al as the base but steel or zinc alloys have aluminum as an alloying metal.
The following metals have widespread adoption as alloying chemical elements –
- Carbon (C): Essential for steel, limited in others.
- Aluminum (Al): Improves grain structure.
- Silicon (Si): Common element in many casting alloys.
- Magnesium (Mg): Key element in aluminum alloys, found in others too.
- Copper (Cu): Minimized to prevent corrosion.
- Manganese (Mn): Essential for maintaining alloy quality.
- Iron (Fe): Common impurity in aluminum alloys.
- Phosphorus (P): Undesirable impurity affecting properties.
- Nickel (Ni): Requires other elements for proper function.
- Vanadium (V): Less preferred alternative to Molybdenum and Manganese.
- Zinc (Zn): Improves corrosion resistance in aluminum and iron alloys.
- Tungsten (W): Enables high-speed properties after heat treatment.
- Molybdenum (Mo): Improves performance at high temperatures.
- Titanium (Ti): Keeps alloys lightweight, used alone or combined.
- Boron (B): Essential in small quantities.
- Zirconium (Zr): Less common element used to modify inclusions.
There are several other elements occasionally used for getting the desired alloy. And they don’t cover a significant portion in cases unless exclusively specified. Beryllium (Be), Cobalt (Co), Selenium (Se), Lithium (Li), Niobium (Nb), Gallium (Ga), Calcium (Ca), Antimony (Sb) are such alloying metals.
Excluding oxygen, only two fundamental gases can be found as impurities in some Al or Fe materials –
- Nitrogen –It’s more like a potential but not a preferred substitute for carbon in certain alloys.
- Hydrogen– The gas exerts some mere positives while causing porosity or cracking in alloys.
Harmful Alloying Elements
Not all alloying metals integrate beneficial advantages in alloys. Some elements cause problems in the alloy itself. Whereas others are plain threats to human health. The blacklisted elements still under constant review by standards are –
- Sulphur (S)– An impurity to exerts adverse influences on properties against some mere benefits.
- Lead (Pb)– This heavy metal with prolonged toxicity mustn’t exceed 0.5% in the composition.
- Cadmium (Cd)– It’s allowed in specified Al/Fe materials up to 0.3% for non-food applications.
- Arsenic (As)– Better to avoid having a high amount present in alloys used for the food industry.
- Mercury (Hg)– Heavily toxic element to causes serious damage to metals upon high presence.
- Chromium (Cr)– A common minor impurity to causes coarse constituents with other impurities.
A minimal quantity is unlikely to cause any serious damage. Several international standards have already set the maximum permissible percentage of contents for those.
Effects of Chemical Elements on Alloys
The ultimate objective of alloying concerns achieving the desired or required properties. Chemical elements in a strictly controlled quantity can deliver the outcome. A brief summary of using these alloying elements in a base metal is as follows –
- Ease of processing to reduce costs.
- A satisfactory weight-to-load ratio.
- Changes in physical properties.
- Improved usability or applicability.
- Changes in mechanical properties.
- Introducing structural integrity.
- Desired finishing for the surfaces.
- High resistance to adverse effects.
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