Fig. 1 Possible distribution of the matrix and nano-sized reinforcement particles in the composite, where the reinforcements are distributed along the grain boundaries of the matrix phase a and the reinforcements are inside the matrix grains b (the open hexagons represent the matrix grains and the open and filled circles represent the reinforcements) [19]

Fig. 2 Schematic of typical powder metallurgy processing scheme [25]

Fig. 3 The variation of the B4C particle size as a function of milling time [29]

Fig. 4 Schematic of ultrasonic solidification processing [32]

Fig. 5 Schematic of the cavitation and steaming effects for nanoparitcle dispersion and wetting in the metal melts: a formation and growth of bubbles; b collapsing of bubbles; c break-up and re-dispersion of nanoparticle clusters [34]

Fig. 6 SEM images showing SiC clusters in AZ91D alloys which were produced by traditional mechanical stirring a and ultrasonic stirring method b [34]

Fig. 7 Morphologies of the TiC particles formed in the Me-Ti-CNT systems: a Me = 50 wt% Cu; b, c Me = 60 wt% Cu; d, e Me = 70 wt% Cu; f Me = 80 wt% Cu; g Me = 50 wt% Al; h, i Me = 60 wt% Al; j Me = 70 wt% Al; k Me = 80 wt% Al; l, m Me = 50 wt% Fe; n Me = 60 wt% Fe; o, p Me = 70 wt% Fe; q, r Me = 80 wt% Fe [56] (The scale bars in the inset images represent 100 nm)

Fig. 8 Schematic diagram of in situ direct reaction synthesis apparatus [58]

Fig. 9 Evolution of Mg-Ti-C mixtures during milling [61]

Fig. 10 Schematic of gas-liquid reaction process [67]