Effect of CNT addition approach on the microstructure and properties of NiAl-CNT nanocomposites produced by mechanical alloying and spark plasma sintering

An approach was offered to synthesize NiAl-CNT intermetallic matrix nanocomposite by mechanical alloying (MA) to ensure the effective distribution of carbon nanotubes (CNTs) within the matrix. For this purpose 0.5 and 1 wt% of CNTs were added to the powder mixture before the completion of reaction between Ni and Al. The resultant powders were compared to the powders obtained from MA of ex situ synthesized NiAl intermetallic compound with CNTs. Bulk samples were fabricated by spark plasma sintering (SPS) that retained the integrity of CNTs in the matrix. Structural evolutions were investigated by X-ray diffractometery (XRD). Field emission scanning electron microscopy (FESEM) micrographs showed that the offered MA approach caused the CNTs to uniformly embed in the in situ synthesized NiAl matrix. Meanwhile better distribution of CNTs resulted in higher density of SPSed bulk nano composite as well as higher hardness up to 5.6 GPa compared to 5.41 of NiAl intermetallic obtained from the same MA time. Fracture toughness showed more than 6.4% increase with bridging and pull out of CNTs and deflection of cracks as toughening mechanisms. (C) 2016 Elsevier Ltd. All rights reserved.