부산대학교 도서관

Master alloys are added to aluminum melts as a source of alloying elements and grain refining agents. The quality of these materials has an important effect on the quality and performance of wrought and cast aluminum end product. Frequently, however, this fact is not appreciated, and master alloys are purchased on the basis of price per lb only. This paper describes techniques used to evaluate master alloys from the user’s standpoint. Particular attention has been given to the development of methods to assess presence and amount of nonmetallic inclusions and the size and distribution of second phase particles such as TiB2. These techniques include met-allographic examination and physical separation of second phase particles from the aluminum matrix followed by a counting operation using a Coulter Counter. Examples of the use of these methods of evaluation are given for Al-Ti, Al-B and Al-Ti-B master alloys. Results obtained with commercial products demonstrate the wide variations observed in quality of these materials in respect to composition, oxide and/or ”dirt“ content, and nature and effectiveness of grain refining agents.