Solidification and grain refinement of Al-Cu and Al-Zn alloys using Ultrasonics, Al3Ti1B grain refiner and their combination

Abstract

The achievement of fine equiaxed grains over large columnar grains in casting stage can significantly improve the downstream processes such as rolling, forging etc. Al-Cu and Al-Zn alloys are very high strength materials used in the aerospace industry, and achieving fine grained structures in these applications means that higher yield strength, better fracture toughness, and machinability and better safety assurance. The primary aim of this research is to understand the efficiency of grain refinement (finest grain size) that can be obtained from addition of solute compositions, application of ultrasonic treatment, 50ppm titanium addition in the form of Al3Ti1B master alloy and a combination of all three conditions. The average grain size measurement of each alloy compositions were measured to understand the extent of grain refinement achieved by each condition. It was found that an increase in solute percentages made restriction of grain growth but introducing ultrasonic treatment simultaneously with solute compositions attained better grain refinement than either solute or Al3Ti1B master alloy alone. The combination of ultrasonic treatment, 50ppm Ti addition and solute made an improvement to the grain refinement of Al-Cu alloys treated with ultrasonic treatment and solute. However, when the three treatments were combined for Al-Zn alloys, there was not a significant improvement in grain size reduction compared to the two treatments alone. Therefore, it can be concluded that in Al-Cu alloys, there is a benefit in applying the ultrasonic treatment and Al3Ti1B master alloy together. On the other hand, Al- Zn alloys doesn’t grain refine even further when ultrasonic treatment and Al3Ti1B inoculant are combined together.