Microstructural evolution and strengthening behavior in in-situ magnesium matrix composites fabricated by solidification processing

In-situ magnesium matrix composites with three different matrix materials (including Mg, AZ91 and AE44 Mg-alloys) were fabricated by injecting cross-linked polymer directly into the molten Mg/Mg-alloys, and having it convert to the 2.5 vol% SiCNO ceramic phase using liquid stir-casting method. In-si...

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Bibliographic Details
Published in:Materials chemistry and physics 2017-06, Vol.194, p.65-76
Main Authors: Chelliah, Nagaraj M., Singh, Harpreet, Surappa, M.K.
Format: Article
Language:English
Subjects:
Alloy solidification
Casting
Crosslinking
Evolution
In-situ processing
Intermetallic compounds
Magnesium base alloys
Magnesium compounds
Matrix materials
Metal matrix composites
Metal matrix composites (MMCs)
Microhardness
Microstructural evolution
Microstructure
Nuclei
Particulate composites
Polymer derived ceramics
Silicides
Slurries
Strengthening mechanisms
Studies
Yield strength
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Summary:In-situ magnesium matrix composites with three different matrix materials (including Mg, AZ91 and AE44 Mg-alloys) were fabricated by injecting cross-linked polymer directly into the molten Mg/Mg-alloys, and having it convert to the 2.5 vol% SiCNO ceramic phase using liquid stir-casting method. In-situ chemical reaction took place within the molten slurry tending to produce 42 and 18 vol% Mg2Si crystals in Mg and AE44 matrix composites, respectively but not in AZ91 matrix composite. Microstructural evolution of Mg2Si crystals was discussed on the basis of availability of heterogeneous nucleation sites and amount of Al-atoms in the molten slurry. The observed micro-hardness and yield strengths are enhanced by factor of four to three as compared to their unreinforced counterparts, and Taylor strengthening was found to be the predominant strengthening mechanism in magnesium and AE44 matrix composites. Summation model predicted the yield strengths of the fabricated composites more preciously when compared to Zhang and Chen, and modified Clyne models. •In-situ magnesium composites were fabricated using liquid stir-casting method.•In-situ pyrolysis of cross-linked polymer has been utilized to obtain ceramic phases.•Mg2Si crystals were formed in magnesium and AE44 matrix composites but not in AZ91 matrix composites.•The variation in size and morphology of Mg2Si crystals with matrix materials are discussed.•Strengthening mechanisms in in-situ composites are analyzed and discussed.
ISSN:0254-0584
1879-3312
DOI:10.1016/j.matchemphys.2017.03.025