Shear enhanced heterogeneous nucleation in some Mg- and Al- alloys

Intensive shearing was applied to alloy melts at temperatures above their liquidus by using a twinscrew mechanism. The sheared melt was then cast into a TP1 mould for microstructural examination. Alloy melts with or without shearing were also filtered using the Prefil technique developed by N-Tech Ltd in order to analyse oxides and other second phase particles. The experimental results showed a significant grain refinement through enhancement of heterogeneous nucleation. The intensive melt shearing converted oxide films and agglomerates into well dispersed fine particles with a narrow size distribution. It was confirmed that the fine oxide particles can act as potent sites for nucleation during the solidification of the sheared melt. This paper presents the experimental results and theoretical analysis of shear enhanced heterogeneous nucleation during solidification of Mg- and Al-alloys. A multi-step heterogeneous nucleation mechanism has been proposed and discussed

Melt conditioning by advanced shear technology (MCAST) for refining solidification microstructures

MCAST (melt conditioning by advanced shear technology) is a novel processing technology developed recently by BCAST at Brunel University for conditioning liquid metal prior to solidification processing. The MCAST process uses a twin screw mechanism to impose a high shear rate and a high intensity of turbulence to the liquid metal, so that the conditioned liquid metal has uniform temperature, uniform chemical composition and well-dispersed and completely wetted oxide particles with a fine size and a narrow size distribution. The microstructural refinement is achieved through an enhanced heterogeneous nucleation rate and an increased nuclei survival rate during the subsequent solidification processing. In this paper we present the MCAST process and its applications for microstructural refinement in both shape casting and continuous casting of light alloys

Melt conditioned direct chill (MC-DC) casting of AA-6111 aluminium alloy formulated from incinerator bottom ash (IBA)

© 2019 by the authors. The melt conditioned direct chill (MC-DC) casting process has been used for the production of billets of AA-6111 alloy formulated from recycled aluminium derived from incinerator bottom ash (IBA). The billets were homogenised and then extruded into planks. Optical metallography of the MC-DC billets showed equiaxed refined grains in comparison to DC and grain refined (DC-GR) billets formulated from the same scrap source. Microstructure evaluation for the extruded planks showed a less extensive peripheral coarse grain (PCG) for the MC-DC sampleInnovate UK. Financial support from the ‘Recycling of Aluminium through Innovative Technology’ (REALITY) Project No. 102797 led by Jaguar Land Rover (JLR)

De-Ironing of Aluminium Alloy Melts by High Shear Melt Conditioning Technology: An Overview

Data Availability Statement: The data presented in this manuscript is available on request from the corresponding author.Copyright: © 2022 by the authors. The main problem of recycling aluminium scrap is the gradual accumulation of impurities, especially iron, which tend to form undesired intermetallic compounds that affect the integrity and the mechanical performance of the castings. In this paper, we aim to provide an overview on the topic of iron removal from aluminium melts through primary intermetallic precipitation and the progress made during the LiME Hub project to understand the process and to develop a more efficient procedure. We cover both thermodynamic analysis and experimental validation. We found that high shear melt conditioning technology enhances the typically slow nucleation and growth of the dense primary intermetallics, speeding up their sedimentation and allowing a faster removal of Fe from the melt by simple gravity sedimentation. It also promotes the formation of smaller and more compact Fe-rich intermetallics, allowing an increased volume fraction recovery and mitigating their effect of being present in the final castings. The technology is not limited to batch processing, with a 90% efficiency, but can also be applied to continuous melt treatment of aluminium scrap, with currently 60% efficiency, and could be combined with other solid–liquid separation techniques to increase the purification efficiency even more.EPSRC (UK) under grant number EP/N007638/1; European Commission under Grant No. 603577; Innovate UK under Project No.102797

Environment-Induced Cracking of High-Strength Al-Zn-Mg-Cu Aluminum Alloys: Past, Present, and Future

Arthur P Armington Professorship; ONR-N00014-18-1-2608 and ONR-N00014-17-1-2573