The microstructure and mechanical properties of an Al–CuO in-situ composite produced using friction stir processing

doi:10.1016/j.matlet.2012.09.028

Materials Letters

Volume 90, 1 January 2013, Pages 26-29

https://doi.org/10.1016/j.matlet.2012.09.028 Get rights and content

Abstract

Friction stir processing (FSP) was applied to produce aluminum based in situ composite from powder mixtures of Al–CuO. Fabricating the in-situ composite required combining the hot working nature of FSP and the exothermic reaction that occurs between aluminum and CuO. The reinforcements in the composite include nanometer-sized Al₂O₃ and Al₂Cu particles. These Al₂O₃ nanoparticles were present in the form of clusters, which were identified as amorphous in the FSPed specimen. The average Al grain size in the FSPed composite was approximately 1 μm. The composite exhibited superior strength and ductility. The major contributions to the high strength of the composite are the ultrafine grained structure of aluminum matrix and the fine dispersion of nanometer-size reinforcing particles inside aluminum grains.

Highlights

► Al–CuO nanocomposites are fabricated using friction stir processing (FSP). ► Nanometer-sized Al₂O₃ and Al₂Cu particles are formed in situ in the composite. ► FSP refines the Al-matrix grain size to approximately 1 μm. ► The Al–CuO composite exhibits yield strength of 284 MPa and good ductility.

Introduction

Aluminum-based metal matrix composites (MMCs) that are reinforced with large amounts of in situ formed intermetallic particles have been successfully fabricated using friction stir processing (FSP) [1], [2], [3], [4]. During FSP, a non-consumable rotating tool with a specially designed pin and shoulder is plunged into the specimen. The friction between the rotating tool and the workpiece raises the local temperature of the material to a range where it can be plastically deformed. A comprehensive literature review on friction stir welding/processing has been given by Mishra and Ma [5]. The formation of in-situ composites using FSP has combined the hot working nature of FSP and the exothermic reaction between aluminum and transition metals. For the recent developments in FSP and its applications for particle-reinforced MMCs, one may refer to the review article provided by Ma [6].

Aluminum matrix composites reinforced with Al₂O₃ particles can be produced using a thermite reaction between aluminum and an oxide of a less reactive metal oxide. Recent researches [7], [8] have shown that aluminum matrix composites reinforced by in situ formed Al₂O₃ nanoparticles can be fabricated by FSP in Al–CeO₂ [7] and Al–TiO₂ [8] systems. These composite exhibited enhanced strength due to the fine dispersion of nanoparticles. In this work, FSP was applied to produce aluminum based in situ composite from powder mixtures of Al–CuO. The Al–CuO system was selected because of the considerable heat release that accompanied the Al–CuO reaction [9], and the Cu that results from Al to CuO reaction can react with Al to form Al₂Cu.

Section snippets

Experimental

The powders used in this study were aluminum (ECKA-Granules, 99.7% purity, −325 mesh) and CuO (CERAC, 99.7% purity, −200 mesh). The powder mixture of Al with 10 mol% CuO (Al–10CuO) was cold compacted at 225 MPa to form a billet of 12×20×88 mm³. The billet was sintered at 773 K for 1 h to improve its strength to sustain the stirring action of the rotating tool in FSP. The tool used was a standard M1.2×6 (diameter of 6 mm and pitch height of 1.2 mm) pin with an 18 mm diameter shoulder. The rotating tool

Results and discussion

The XRD patterns of the sintered sample and the sample produced using FSP are shown in Fig. 1a. Diffraction peaks of Al, CuO, Cu₂O, and Cu appear in the XRD pattern of the sintered sample. The presence of Cu₂O indicates partial reduction of CuO occurring in sintering. After FSP, the intensity of the CuO peak significantly decreased as compared with the sintered sample. After four passes of FSP, the Al₂Cu peaks were clearly observed, but Al₂O₃ could not be found in the XRD pattern. The TEM

Summary

Friction stir processing (FSP) was applied to produce aluminum based nanocomposite from powder mixtures of Al and CuO. This technique has combined the hot working nature of FSP and the exothermic reaction between Al and CuO. The composite was reinforced with nanometer sized particles of Al₂O₃ and Al₂Cu, which were formed in-situ during FSP. These Al₂O₃ nanoparticles were present in the form of clusters, which were identified as amorphous in the FSPed specimen. The fine structure of these

Acknowledgement

The authors gratefully acknowledge the sponsorship by the National Science Council of Taiwan, ROC under Grant No. NSC96-2628-E-110-009-MY3.

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The microstructure and mechanical properties of an Al–CuO in-situ composite produced using friction stir processing

Abstract

Highlights

Introduction

Section snippets

Experimental

Results and discussion

Summary

Acknowledgement

Scr Mater

Acta Mater

Intermetallics

Mater Sci Eng A

Mater Sci Eng R