Generation of ultrafine Al-Cu-Si eutectics alloys by containerless rapid solidification

Abstract

Ultrafine structured metals have been investigated in recent years. Their remarkable high strength may contrast with conventional coarse-structured materials. However, applications of these alloys containing high Cu and Si contents become limited due to their low plasticity. Recently, combinations of bimodal ultrafine eutectics (i.e., a ternary eutectic matrix (Al+Al2Cu+Si) with a dispersion of a binary eutectic (Al+Al2Cu)) have resulted in improved plasticity. The M2PS (Microestrutura e Propriedades em Processos de Solidificação) research group from the Federal University of Sao Carlos (UFSCar) is already investigating the ternary Al-15%Cu-7%Si, Al-22%Cu-7%Si and Al-26%Cu-7%Si alloys through transient directional solidification (DS) experiments followed by a robust analysis of the microstructures and compressive properties. Such studies are being conducted in the frame of the ongoing project funded by FAPESP (Grant number: 2017/12741-6) entitled: "Application of experimental solidification techniques, characterization of microstructure and properties in the evaluation of eutectic and hypereutectic Al-base and Zn-base alloys".This means a possibility of comprehending the formation of the eutectics and their natures on regard to the applied cooling rates and growth rates. However, cooling rates through DS experiments are limited to the range between 10-1-102 K.s-1. In order to surpass such limitation, the production and examination of impulse atomized powders could be very useful. This technique will permit rapid solidified microstructures to be examined. The evolutions of the eutectic structures as a function of powder size will be emphasized. The thermal history will be determined quantitatively from a quantitative analysis of the solidified microstructure. Characteristics of the binary and ternary constituents such as their fractions, sizes and distributions will be determined since those are the very important aspects affecting mechanical properties.The ultrafine eutectic can provide a remarkable combination of plasticity and strength, which depends on the generated microstructure. Optimization techniques through solidification can be applied in order to preprogram a certain manufacturing process so that both microstructures and properties could be managed. This is the main purpose of this project, dealing with both solidification and rapid solidification of Al-Cu-Si alloys.The previous research projects between the Advanced Materials and Processing Laboratory (AMPL) of the Department of Chemical and Materials Engineering at University of Alberta (UofA) and the research group M2PS of the Department of Materials Engineering at UFSCar have generated mutual benefits to both of our research groups. A variety of topics regarding "Solidification of metals" have been studied in previous projects between these research groups, which include: CALDO-FAPESP (grant Number 2013/50375-0); FAPESP Research Fellowships Abroad (Grant number 2016/10596-6) and NSERC CRD with Equispheres. This means that our previous project funded as a result of the joint call between FAPESP and the CALDO consortium achieved all objectives. (AU)