Article JOURNAL OF COMPOSITE MATERIALS Development of magnesium-based hybrid metal matrix composite through in situ micro, nano reinforcements Harprabhjot Singh 1 , Deepak Kumar 1 and Harpreet Singh 2 Abstract Present work aims at developing Magnesium based metal matrix composite (MMC) through in-situ reaction. In-situ generation of micro and nano particles in the Mg-melt is supposed to have a better bonding with the matrix. Ceric ammonium nitrate (CAN) is added to initial Magnesium melt (with an aim to generate CeO 2 and MgO through in-situ reaction) at temperatures of 670  C and 870  C. The developed MMCs are solution treated to get rid of intermetallic. The nature of particles is explored with X-ray diffraction (XRD) and Energy dispersion spectroscopy (EDS). The morphology and sizes of particles are keenly jotted using scanning electron microscope (SEM). Mechanical responses of developed MMCs are recorded through Hardness, Compression and scratch tests. The compression fractured surfaces are analyzed with SEM and scratched samples are analyzed on 3 D optical profilometer to explore deformation behavior. The observations indicate the in-situ formation of CeO 2 , MgO and CeMg 12 intermetallic phases in different types and sizes. Further, these particles are responsible for improved mechanical properties. The findings are supported by the contribution of different strengthening mechanisms. Keywords Magnesium, in situ hybrid composite, CeO 2 , MgO, strengthening mechanism Introduction Mg alloys and Mg based Metal matrix composites (MMCs) have vast application in automotive, aero- space and biomedical applications. 1–6 MMCs have edge over alloys in high temperature applications, where intermetallic are unstable. Moreover, MMnCs (Metal matrix nano composites) can improve ductility as well. 5,7 Mg based MMCs can find better place over Mg alloys for tribological application where tempera- ture can surpass 150  C. 8 In general, MMC can be produced using powder metallurgy or methods involving molten metal. 4 Mg- bio ceramic composites have been made by sintering. 9 Stir casting is common route for preparing MMCs. MMCs can be produced ex-situ (addition of ceramics) or in-situ (production of ceramics). Further, Magnesium is highly reactive and tries to reduce reinforcements, thus impairing the properties of rein- forcements. 10 This aspect adds more complexity to the in-situ generation of ceramic particles. Magnesium does not form carbides easily; thus, carbides of other metals are stable in it. 4 Magnesium reacts with alumina in the melt state to form MgO. 4 Kujur et al. 11 have shown the stability of ceria (Rare earth oxide) in the Magnesium matrix. Goh et al. 12,13 synthesized Mg- MgO nanocomposite and Mg-yttria nano composite with the DMD technique. They found good interfacial adhesion between Mg matrix and MgO particles. The above discussion can be briefed as, Rare earth oxides, metal carbides and Magnesium oxide are stable in mag- nesium melt. The common issues associated with developments of MMCs are poor wettability of rein- forcement, non-uniform distribution, agglomeration of 1 Centre for Automotive Research and Tribology, Indian Institute of Technology Delhi, India 2 Department of Mechanical Engineering, Indian Institute of Technology Ropar, India Corresponding author: Deepak Kumar, Centre for Automotive Research and Tribology, Indian Institute of Technology Delhi, Delhi 110016, India. Email: dkumar@itmmec.iitd.ac.in Journal of Composite Materials 0(0) 1–15 ! The Author(s) 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0021998320946432 journals.sagepub.com/home/jcm