Production of MA956 Alloy Reinforced Aluminum Matrix Composites by Mechanical Alloying

Luiz Antonio Carlos Moutinho Gomes,Jose Luis González-Carrasco,Dilermando Nagle Travessa,Katia Regina Cardoso,Marcela Lieblich

doi:10.1590/1516-1439.346114

Abstract

Aluminum matrix composites (AMC) are attractive structural materials for automotive and aerospace applications. Lightweight, environmental resistance, high specific strength and stiffness, and good wear resistance are promising characteristics that encourage research and development activities in AMC in order to extend their applications. Powder metallurgy techniques like mechanical alloying (MA) are an alternative way to design metal matrix composites, as they are able to achieve a homogeneous distribution of well dispersed particles inside the metal matrix. In this work, aluminum has been reinforced with particles of MA956, which is an oxide dispersion strengthened (ODS) iron base alloy (Fe-Cr-Al) of high Young’s modulus and that incorporates a small volume fraction of nanometric yttria particles introduced by mechanical alloying. The aim of this work is to investigate the use of MA to produce AMC reinforced with 5 and 10 vol.% of MA956 alloy particles. Homogeneous composite powders were obtained after 20 h of milling. The evolution of morphology and particle size of composite powders was the typical observed in MA. The composite powders produced with 10 vol.% MA956 presented a more accentuated decrease in particle size during the milling, reaching 37 μm after 50 h. The thermal stability of the composite and the existence of interface reactions were investigated aiming further high temperature consolidation processing. Heat treatment at 420 °C resulted in partial reaction between matrix and reinforcement particles, while at 570 °C the extension of reaction was complete, with formation in both cases of Al-rich intermetallic phases.

Highlights

Aluminum matrix composites have, in general, improved properties at elevated temperatures, higher specific strength and wear resistance than unreinforced matrix alloy[1,2,3,4,5]
The composite powders produced with 10 vol.% MA956 presented a more accentuated decrease in particle size during the milling, which can be observed by comparing the micrographs of Figures 1b and c from powders milled for 20 h
These results suggest that the white phase, spot 1, is the remaining α-Fe (MA956 alloy), while the grey phase, spot 2, is an intermetallic phase enriched in Al, similar to that found in the Al_5 vol.% MA956

Summary

Introduction

In general, improved properties at elevated temperatures, higher specific strength and wear resistance than unreinforced matrix alloy[1,2,3,4,5]. Aluminum matrix composites reinforced with ceramic particles have already found several applications. They suffer from some drawbacks due to the high abrasiveness and brittleness of the ceramics. Intermetallics particles have been used as an alternative because of their lower abrasiveness and brittleness[6,7,8]. Intermetallics have thermal expansion coefficients closer to the aluminum, resulting in a decrease of the residual stresses in the reinforcement-matrix interface, reducing problems related to thermal fatigue[9]

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Conclusion