Controlling composition using Master Alloys

Create materials that meet specific needs by adding master alloys to the mix

It’s important to choose the right materials for a job. Using inferior or unsuitable materials can make completing a project more difficult or even derail it entirely. In the metals industry, combinations of metals, called alloys, are generated to meet the specific performance requirements of a wide variety of applications. Aircraft parts, for example, need to be strong and resistant to heat, cracks and corrosion.

Aluminum alloys containing materials like copper, magnesium and zinc fit that bill. However, if an aircraft manufacturer needs two parts to be welded together, an alloy containing copper could cause solidification cracking. In that case, another alloy with a different combination of elements — one that can withstand the welding process — would be chosen.

Producing alloys requires knowledge of an element’s inherent properties, such as corrosion resistance, ductility and strength, and how it will react when combined with other elements. Variations in densities, melting points and non-uniform compositions can cause problems during the alloying process.

A master alloy is a base metal, such as aluminum or copper, that’s combined with a high percentage of one or two other elements. Master alloys are semi-finished products used as raw materials. They are produced in various shapes: slab, waffle, ingot, lumps, rods, and are engineered with characteristics, such as the ability to dissolve quickly and at lower temperatures.

Melting and casting operations will find master alloys useful when adding small amounts of compounds that have significant differences in melting point. Master alloys also are used to change the composition of the liquid metal to achieve a specific property, such as mechanical strength, electrical conductivity or ductility, or to reach a particular chemical specification. As a result, they are classified under different categories. Those that are added to increase strength are referred to as hardeners. Others are called grain refiners and provide control over the alloy’s structure. There also are master alloys that are deoxidizers and degasifiers. A boron copper or lithium copper master alloy, for example, is a good deoxidizer and degasifier for copper- and nickel-based alloys because it does not reduce conductivity.

Because there are many different types of master alloys, it’s important to be knowledgeable about their functions, forms and purities. All these characteristics ultimately have an effect on the final product. Any amount of excess element in an alloy will affect its purity. And even insignificant levels of impurities should be monitored because they can have an impact on the finished product.

A master alloy’s quality largely depends on attention to detail during its production. Manufacturers who have well-trained personnel, state-of-the-art equipment, quality assurance and inspection systems in place, and are certified to standards, such as ISO 9001:2000 can more easily assure customers that the composition of the alloy is sufficient for their needs. In addition, alloy manufacturers can use methods like optical emission spectrometry, which provides rapid analysis of metal samples, and XRF testing to verify composition.

Experienced metallurgists are a valuable resource when working with molten metals. They can collaborate with manufacturers to troubleshoot problems with their alloys, answer questions and ensure finished products meet performance expectations.