Influence of Fiber Distribution and Grain Size on the Mechanical Behavior of Friction Stir Processed Mg-C Composites

Conference (2012, November 12)

Short C fibers-Mg matrix composites have been produced by friction stir processing sandwiches made of a layer of C fabric stacked between two sheets of either the ductile Mg alloy AZ31B, or of the less ... [more ▼]

Short C fibers-Mg matrix composites have been produced by friction stir processing sandwiches made of a layer of C fabric stacked between two sheets of either the ductile Mg alloy AZ31B, or of the less ductile alloy AZ91D, that is capable of age hardening. It has been shown that the choice of the optimal experimental parameters for the production of sound composites was strongly dependent on the nature of the matrix. 3D X-ray tomography reveals that the fibers orient along the onion rings and that they are more or less fragmented depending on the local shear stress during the process. The fiber volume fraction is increased when the nugget volume decreases in particular for the AZ91D base material and for a high advancing speed for the AZ31B base material. The fiber volume fraction influences directly the grain size, the hardness and the tensile properties of the composites. [less ▲]

Friction Stir Processing of Magnesium Matrix Composites reinforced with Carbon Fibres: Influence of the Matrix Characteristics and of the Processing Parameters on Microstructural Developments

in W.J.Poole, K.U.Kainer (Ed.) Proceedings of the 9th International Conference On Magnesium Alloys and their Apllications (2012, July 12)

Processing of magnesium matrix composites reinforced with C fibres by ‘liquid state’ methods such as squeeze casting are usually impaired by the poor wettability of C substrates by liquid Mg. As a ... [more ▼]

Processing of magnesium matrix composites reinforced with C fibres by ‘liquid state’ methods such as squeeze casting are usually impaired by the poor wettability of C substrates by liquid Mg. As a consequence, ‘solid state’ processes such as Friction Stir Processing (FSP) appear as very promising alternative processing routes for the production of C-Mg composites. And, more particularly, FSP of a C fabric between two sheets of the fairly ductile Mg alloy AZ31B was shown to be a simple and innovative process for a large-scale production of magnesium matrix composites reinforced with short C fibres. In the present work, FSP of a C fabric between two metal sheets or thin plates has been performed using two different Mg alloys exhibiting quite different mechanical behaviours, i.e. alloy AZ31B and the more brittle alloy AZ91D. And the effect of the matrix characteristics, along with the influence of the FSP experimental parameters such as the rotational and advancing speeds, on the microstructural changes occuring upon processing have been carefully studied. A particular attention has been given to the fragmentation and distribution of the C fibres, as well as to the recrystallisation, solutionising and precipitation processes taking place in the Mg matrix. [less ▲]

Microstructure and mechanical properties of stir processed magnesium matrix composites reinforced with carbon fibres

Conference (2012, January 26)

Mg-Al-Zn alloys have been reinforced with carbon fibres using friction stir processing (FSP) which appears as a promising alternative for the large-scale production of C-Mg composites. The process has ... [more ▼]

Mg-Al-Zn alloys have been reinforced with carbon fibres using friction stir processing (FSP) which appears as a promising alternative for the large-scale production of C-Mg composites. The process has shown its ability to produce sound composites with enhanced strength compared to the non-reinforced alloys. The C fabric is fragmented in short fibres leading to a reduction in grain size and an improved hardness. [less ▲]

C FIBERS - MG MATRIX COMPOSITES PRODUCED BY SQUEEZE CASTING AND FRICTION STIR PROCESSING: Microstructure & Mechanical Behaviour

Poster (2011, August)

Mg matrix composites appear as suitable competitors to Al alloys, as they allow for a significant weight reduction while exhibiting potentially comparable mechanical properties. A large variety of ... [more ▼]

Mg matrix composites appear as suitable competitors to Al alloys, as they allow for a significant weight reduction while exhibiting potentially comparable mechanical properties. A large variety of processing routes have already been considered for their production, including 'liquid state' processes such as squeeze casting. However these techniques necessitate a very careful control, simultaneously, of the solidification process, the wetting behaviour and the possible interfacial reactions between the reinforcements and the molten metal. And this is more particularly true in the case of Mg matrix composites with carbon fibers reinforcements, as Mg alloys are known to exhibit a poor wetting behaviour on carbon substrates. As a consequence, 'solid state' processing routes such as friction stir processing, that has been developed more recently, provide promising alternatives for the production of C-Mg composites. In the present work, Mg-Al-Zn alloys have been reinforced with carbon fibers using squeeze casting and friction stir processing. The microstructures and mechanical behaviour of composites produced by both processes have then been characterised and compared to those of non-reinforced samples, with a particular attention to the damage mechanisms prevailing in the composite materials. As a result, both processes have been compared in terms of the properties of their final products and hence their ability to produce sound composites. [less ▲]