Similar to a restaurant chef using small additions of spices to fine-tune his dishes, the metal industry uses master alloys to adjust the properties of its products.
A master alloy is a base metal such as aluminium, copper or nickel combined with a relatively high percentage of one or two other elements. An example is AlTi10 - a binary alloy consisting of 10% titanium in aluminium. A master alloy is a semi-finished product. It is manufactured for use as a raw material by the metals industry. Master alloys are produced in various shapes. Examples are: ingot, waffle plate, rod in coils, etc.
Master alloys are used worldwide. Invariably they are found in plants where metal is melted, alloyed with various elements and then cast into shapes. This can be aluminium, iron, steel or even a precious metal such as gold.
There are various reasons for adding master alloys to a melt. One of the main applications is composition adjustment, i.e. changing the composition of the liquid metal to achieve the desired chemical specification. Another important application is structure control - influencing the microstructure of a metal during the casting and solidification process in order to change its properties. Such properties include mechanical strength, ductility, electrical conductivity, castability or surface appearance. A master alloy is sometimes also referred to as "hardener", "grain refiner" or "modifier" depending on its application.
Reasons for using a master alloy instead of a pure metal can be economical, technical or both. Some elements show high losses - or poor yield - when added in pure form. Others will not dissolve at all at the furnace temperature prevailing in a casthouse. A master alloy often provides the solution, as it dissolves much quicker at lower temperatures, saving valuable energy and production time.
The master alloy industry uses specialised equipment such as high temperature induction furnaces to produce the alloy composition suitable for use by the regular metals industry.
Master alloy fabrication is a truly specialised field.