Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.

Microstructures and Tensile Properties of Ultrafine-Grained Ni-(1-3.5) wt% SiCNP Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites (Ni-SiC_NP), with a SiC_NP content ranged from 1 to 3.5 wt%, were prepared using mechanical alloying and spark plasma sintering. In addition, unreinforced pure nickel samples were also prepared for comparative purposes. To characterize the microstructural properties of both the unreinforced pure nickel and the Ni-SiC_NP composites transmission electron microscopy (TEM) was used, while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests. TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample, whereas, for the Ni-SiC_NP composites, the presence of nano-dispersed SiC_NP and twinning crystals was observed. These homogeneously distributed SiC_NP were found located either within the matrix, between twins or on grain boundaries. For the Ni-SiC_NP composites, coerced coarsening of the SiC_NP assembly occurred with increasing SiC_NP content. Furthermore, the grain sizes of the Ni-SiC_NP composites were much finer than that of the unreinforced pure nickel, which was considered to be due to the composite ball milling process. In all cases, the Ni-SiC_NP composites showed higher strengths and hardness values than the unreinforced pure nickel, likely due to a combination of dispersion strengthening (Orowan effects) and particle strengthening (Hall-Petch effects). For the Ni-SiC_NP composites, the strength increased initially and then decreased as a function of SiC_NP content, whereas their elongation percentages decreased linearly. Compared to all materials tested, the Ni-SiC_NP composite containing 1.5% SiC was found more superior considering both their strength and plastic properties.