Effect of Small Additions of Cr, Ti, and Mn on the Microstructure and Hardness of Al–Si–Fe–X Alloys

Víctor Aranda,Ignacio Figueroa,Gabriel Lara-Rodríguez,Gonzalo González,J García-Hinojosa

doi:10.3390/met9020136

Abstract

The Al–Si–Fe system has drawn the attention of the scientific community due to its capacity to replace parts in several manufacturing industries, as this alloy system is very sensitive to small additions of transition metals. Therefore, the aim of this work is to study the effect of Cr, Ti, and Mn additions in the Al–20Si–5Fe (wt. %) alloy and to study the modification of the iron intermetallic and the microstructural refinement through the formation of secondary phases. Al–20Si–5Fe–X (X = Cr, Mn and Ti at 1.0, 3.0, and 5.0 wt. %) alloy ingots were prepared by arc melting furnace. The elemental chemical analysis was performed by X-ray fluorescence spectrometry (XRF). The microstructure of all samples was investigated by scanning electron microscopy and X-ray diffraction. Finally, microhardness was measured in order correlate the hardness with the formation of the different compounds. The highest hardness was found for the alloy with the 5 wt. % Cr. The addition of Ti and Mn raised the hardness by ~35 HVN (Vickers microhardness) when compared to that of AlSiFe master alloy. Important changes were also observed in the microstructure. Depending on the Cr, Ti, and Mn additions, the resulting microstructure was dendritic (CrFe), acicular (Ti5Si3), and “bone like” (Mn0.2Fe0.8), respectively.

Highlights

Aluminum (Al) alloys have many applications, especially in the automotive and the aeronautical industry [1,2,3]
The aim of this work is to study the effect of Cr, Ti, and Mn additions on the Al–20Si–5Fe alloy microstructure
The weighed elements were melted on a water-cooled copper hearth in the arc furnace to produce alloy buttons of mass typically between 3 and 5 g

Summary

Introduction

Aluminum (Al) alloys have many applications, especially in the automotive and the aeronautical industry [1,2,3]. AlSiFe based alloys have been of interest of the scientific community due to their ability to replace cast iron parts in several manufacturing industries. The properties of these alloys are greatly dependent on the morphology, size, and distribution of primary silicon (Si) particles [4,5,6,7,8]. It has been demonstrated that alloying Al-based alloys with transition metals such as Fe, Mn, or Cr considerably improves the thermal stability of these alloys, being important for applications at elevated temperatures These elements have low diffusion coefficients and low solubility in the Al solid solution, forming thermally stable phases [3]

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