Role of ultrasonic treatment, inoculation and solute in the grain refinement of commercial purity aluminium

Abstract

The present study investigates the influence of ultrasonic treatment on the grain refinement of commercial purity aluminium with a range of Al3Ti1B master alloy additions. When the aluminium contains the smallest amount of added master alloy, ultrasonics caused significant additional grain refinement compared to that provided by the master alloy alone. However, the influence of ultrasonics on grain size reduces with increasing addition of the master alloy which adds additional TiB2 particles and Ti solute with each incremental addition. Applying the Interdependence model to analyse the experimentally measured grain sizes revealed that the results of this study and those from similar experiments on an Al-2Cu alloy were consistent when the alloy compositions are converted to their growth restriction factors (Q) and that increasing Q had a major effect on reducing grain size and increasing grain number density. Compared with the application of ultrasonic treatment where an order of magnitude increase in the grain number density is achieved, an increase in the Ti content over the range of master alloy additions, causes the grain number density to increase by approximately three times.

Evolution of the As‐Cast Grain Microstructure of an Ultrasonically Treated Al–2Cu Alloy

“…With UST, low G and high R throughout the bulk melt create a favorable thermal environment for the formation of equiaxed dendritic grains. The Interdependence Theory also predicts that a low temperature gradient will reduce or even eliminate the Nucleation‐Free Zone (NFZ) in which nucleation is not able to occur due to insufficient undercooling …”

Influence of Vibration Treatment and Modification of A356 Aluminum Alloy on Its Structure and Mechanical Properties

“…The strain resistance of metallic materials in the solid state can be increased by using an alloy structure refinement [2,3]. In practice, the best-known methods for obtaining a fine-grained microstructure of cast aluminum alloys are (1) melt treatment using external fields (vibration [4][5][6], ultrasound [7,8], and electromagnetic stirring [9,10]); and (2) the use of grain refining master alloys [11][12][13].…”

The Poisoning Effect of Al and Be on Mg—1 wt.% Zr Alloy and the Role of Ultrasonic Treatment on Grain Refinement

“…The liquid treatment, UST-L, produces excellent refinement when the alloy contains more potent substrates and solute (Atamanenko et al, 2010;Wang et al, 2017c;Nagasivamuni et al, 2019a). The solidification treatment UST-S, on the other hand, can produce refinement in pure metals (Wang et al, 2017d;Nagasivamuni et al, 2018) and dilute alloys (Wang et al, 2014(Wang et al, , 2016a(Wang et al, , 2017bSrivastava et al, 2017) without potent substrates.…”

“…This attractive feature of UST facilitates opportunities to explore new alloy systems for which an appropriate grain refiner is unavailable (Nagasivamuni et al, 2018). Significant grain refinement has been reported for pure metals (Nagasivamuni et al, 2018(Nagasivamuni et al, , 2019b, binary alloys without refiners (Qian et al, 2010;Srivastava et al, 2017;Wang et al, 2017b) and in the presence of potent grain refiners (Ramirez et al, 2008;Atamanenko et al, 2010;Wang et al, 2017d;Nagasivamuni et al, 2019a). The application of UST to alloys containing elements that poison nucleation has also resulted in improved refinement.…”