Fabrication of Ni, Si and Mg Supersaturated Solid Solutions in Al by Mechanical Alloying

A Sedano,S.A Serna,A Torres-Islas,A Molina,R.A Rodr�Guez-D�Az

doi:10.3844/ajeassp.2020.61.71

Abstract

In this work, a comparison between the synthesis process of nanostructured Al base alloys modified with Si, Ni and Mg and the formation of their respective supersaturated solid solution is presented. The samples were obtained via Mechanical Alloying (MA) at a speed of 300 RPM for 2, 5, 10, 20 and 30 h under an inert Ar atmosphere. Lattice parameter evolution, semiquantitative X-Ray Diffraction Analysis and SEM micrographs were correlated to determine the attained solubility in the Al matrix. The results showed that powder refinement and solubility rates are directly affected by the hardness of the solute element and the limiting solubility in equilibrium state respectively. Therefore the Al-Mg alloy achieved the highest solubility of the samples after 10 h of milling, meanwhile, the Al-Si alloy showed the lowest solubility even after 20 h of milling. Microstructural analyses by X-Ray Diffraction revealed that the lattice parameter showed different behavior depending on the alloy system, in some cases showing a deviation from the behavior predicted by Vegard's law. Finally, this work demonstrates that the successful synthesis of supersaturated solid solutions via MA is dependent on the alloy system as well as milling conditions.

Highlights

New technological developments require advanced materials with properties such as lightweight, high strength, fatigue resistance and corrosion resistance (Atul et al, 1993; Heinz et al, 2000; Yvon and Carré, 2009), but on the other hand, it's desirable that they are low cost to produce with raw material availability
Initial powders Scanning Electron Microscopy (SEM) micrographs (Fig. 2) show different morphological characteristics for the powders, consisting in spherical for those of Al (Fig. 2a), amorphous for those of Mg (Fig. 2d) and irregular for those of Ni (Fig. 2b) and Si (Fig. 2c) powders. Their difference in morphology is due to the use of distinct production methods, Al powders where atomized machining was used for those of Ni and Si and mechanical milling processing was used for the Mg samples
In this work is demonstrated the viability of producing Solid Solutions (SSS) of Al-3wt%Si, Al-3wt%Mg and Al3wt%Ni by mechanical alloying under low energy milling conditions

Summary

Introduction

New technological developments require advanced materials with properties such as lightweight, high strength, fatigue resistance and corrosion resistance (Atul et al, 1993; Heinz et al, 2000; Yvon and Carré, 2009), but on the other hand, it's desirable that they are low cost to produce with raw material availability. Good candidates include microstructurally designed Al alloys, capable of being tailored to withstand harsh environments while exhibiting good mechanical properties essential for advance engineering applications (Reed et al, 2009; Nie and Muddle, 1998; Vajpai et al, 2015). The main advantage of materials with such strengthening mechanisms is that they can be designed microstructurally for their intended application (Eskin, 2003), this is done via different heat treatment regimens that produces metal matrix composites (MMC) with a refined microstructure and a controlled precipitation of second phases capable of withstanding harsh environments while exhibiting high strength, corrosion resistance and good wear resistance. The development of new low weight Al alloys with improved mechanical properties compasses the investigation of SSS, their heat treatment regimens and the mechanisms involved in their synthesis via different techniques. The MA process consists of a more flexible method to produce SSS but one that requires the optimization of the milling parameters to produce the required system conditions to obtain SSS alloys

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Methods

Results

Discussion

Conclusion