Copper particles were incorporated and retained in elemental state in an aluminium matrix by friction stir processing thereby producing a non-equilibrium particulate composite. The processed Al-Cup composite exhibited improved strength with significantly high ductility. The composite was stable up to a temperature of more than 300uC. Thermal exposure at 350uC for more than 10 min led to diffusion of Cu atoms into the Al matrix forming a core-shell type structure in the Cu particles and thus producing an Al-Cu core-shell composite. The shell consists of multiple layers, the thickness of which was controllable. © 2015 Institute of Materials, Minerals and Mining

Ranjit Bauri

Department of Metallurgical and Materials Engineering

Aluminum

Friction

Friction stir welding

Grain refinement

Metallic matrix composites

Shells (structures)

Structure (composition)

ALUMINIUM MATRIX

COPPER PARTICLES

Core-shell

Core-shell composites

CORE-SHELL PARTICLE

Friction stir processing

PARTICULATE COMPOSITES

thermal exposure

PARTICLE REINFORCED COMPOSITES

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Development of Cu particles and Cu core-shell particles reinforced Al composite

Materials Science and Technology (United Kingdom)

The present investigation shows that alternate to the ceramic particles, hard metallic particles can be used as reinforcement in an aluminum matrix to achieve a good strength–ductility combination in a composite. Titanium particles were incorporated into aluminum by friction stir processing (FSP) to process an Al-Ti particulate composite. FSP led to uniform distribution of the particles in the stir zone without any particle–matrix reaction, thereby retaining the particles in their elemental state. Fracture and twinning of the Ti particles with different frequency of occurrence on the advancing and retreating sides of the stir zone was observed. Twinning of the particles was studied by focused ion beam-assisted transmission electron microscopy. The processed Al-Ti composite exhibited a significant improvement in strength and also retained appreciable amount of ductility. The thermal stability of the fine-grained structure against abnormal grain growth (AGG) was improved by the Ti particles. The AGG in the Al-Ti composite occurred at 713 K (440 °C) compared to 673 K (400 °C) in the unreinforced aluminum processed under the same conditions. On the other hand, the particle–matrix reaction occurred only at 823 K (550 °C), and hence the Ti particles were thermally more stable compared to the matrix grain structure. © 2016, The Minerals, Metals & Materials Society and ASM International.

Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science

Al-Ti Particulate Composite: Processing and Studies on Particle Twinning, Microstructure, and Thermal Stability

Friction deposition is one of the promising new techniques for additive manufacturing. In this work, an aluminum matrix composite reinforced with titanium particles was successfully friction deposited. The multi-layer composite friction deposits showed well-bonded layers, very fine grain size, and uniformly distributed titanium particles. While the reinforcement/matrix interfaces showed no reaction products, the layer interfaces showed thin intermetallic bands. These brittle intermetallic bands were found to strongly affect the ductility of the multi-layer composite friction deposits in the build direction. However, the composite friction deposits performed satisfactorily in compression tests as well as in single-layer tensile tests. © 2015 Elsevier B.V.

Materials Science and Engineering A

Friction deposition of titanium particle reinforced aluminum matrix composites

Nickel particles were embedded into an Al matrix by friction stir processing (FSP) to produce metal particle reinforced composite. FSP resulted in uniform dispersion of nickel particles with excellent interfacial bonding with the Al matrix and also lead to significant grain refinement of the matrix. The novelty of the process is that the composite was processed in one step without any pretreatment being given to the constituents and no harmful intermetallic formed. The novel feature of the composite is that it shows a three fold increase in the yield strength while appreciable amount of ductility is retained. The hardness also improved significantly. The fracture surface showed a ductile failure mode and also revealed the superior bonding between the particles and the matrix. Electron backscattered diffraction (EBSD) and transmission electron microscopy analysis revealed a dynamically recrystallized equiaxed microstructure. A gradual increase in misorientation from sub-grain to high-angle boundaries is observed from EBSD analysis pointing towards a continuous type dynamic recrystallization mechanism. © 2010 Elsevier B.V.

Processing, microstructure and mechanical properties of nickel particles embedded aluminium matrix composite

Friction stir processing was carried out on commercially pure aluminium, and a detailed microstructural characterisation was performed by electron backscattered diffraction and transmission electron microscopy. Friction stir processing resulted in significant grain refinement with narrow grain size distribution. The microstructure showed fine and equiaxed grains, with some ultrafine grains being also observed. Electron backscattered diffraction studies showed majority of the boundaries to be high angle, confirming the occurrence of dynamic recrystallisation (DRX). Transmission electron microscopy observations revealed dislocation arrangement into subgrain boundaries, grains having different dislocation densities and in different stages/degrees of recovery. Electron backscattered diffraction analysis also revealed a progressive transformation of sub-grain boundaries into high angle grain boundaries. A multimechanism of dynamic recovery, continuous DRX and discontinuous DRX seems to be operating during the process. The microstructure is not affected by changing the rotation speed from 640 to 800 rev min -1, except that the grain size was marginally larger for higher rotational speed. © 2011 Institute of Materials, Minerals and Mining.

Materials Science and Technology

Microstructural characterisation of friction stir processed aluminium

Nickel particulate reinforced aluminium matrix composite was processed without formation of deleterious Al3Ni intermetallic by friction stir processing (FSP). FSP resulted in uniform dispersion of nickel particles in the aluminium matrix with excellent interfacial bonding and also lead to grain refinement of the matrix. The composite exhibited a threefold increase in the yield stress (0.2% proof stress). The most novel feature of the composite is that an appreciable amount of ductility is retained while the strength increases significantly. The microstructure evolution was studied by transmission electron microscopy and electron backscattered diffraction analysis. EBSD analysis showed a dynamically recrystallized equiaxed microstructure having a considerable fraction of low-angle boundaries. TEM observations revealed that these low-angle boundaries are essentially subgrain boundaries formed by dislocation rearrangement and absorption during friction stir processing. © 2009 Elsevier B.V. All rights reserved.

Materials Letters

Nickel particle embedded aluminium matrix composite with high ductility

Reactive friction stir processing of AA 5052–TiO2nanocomposite: process–microstructure–mechanical characteristics

Materials & Design

Effect of processing parameters on fabrication of Al–Mg/Cu composites via friction stir processing

Journal	Materials Science and Technology (United Kingdom)
Publisher	Maney Publishing
ISSN	02670836
Open Access	No