CNTs/TiC Reinforced Titanium Matrix Nanocomposites via Powder Metallurgy and Its Microstructural and Mechanical Properties

Abstract

By using pure titanium powder coated with unbundled multiwall carbon nanotubes (MWCNTs) via wet process, powder metallurgy (P/M) titanium matrix composite (TMC) reinforced with the CNTs was prepared by spark plasma sintering (SPS) and subsequently hot extrusion process. The microstructure and mechanical properties of P/M pure titanium and reinforced with CNTs were evaluated. The distribution of CNTs and in situ formed titanium carbide (TiC) compounds during sintering was investigated by optical and scanning electron microscopy (SEM) equipped with EDS analyzer. The mechanical properties of TMC were significantly improved by the additive of CNTs. For example, when employing the pure titanium composite powder coated with CNTs of 0.35 mass%, the increase of tensile strength and yield stress of the extruded TMC was 157 MPa and 169 MPa, respectively, compared to those of extruded titanium materials with no CNT additive. Fractured surfaces of tensile specimens were analyzed by SEM, and the uniform distribution of CNTs and TiC particles, being effective for the dispersion strengthening, at the surface of the TMC were obviously observed.

High-temperature properties of extruded titanium composites fabricated from carbon nanotubes coated titanium powder by spark plasma sintering and hot extrusion

“…Unfortunately, the exact strengthening mechanism by the remained CNTs in the Ti composites at room and elevated temperatures is still unclear because the exact amount of CNTs transformed to TiC is unknown. However, the remained CNTs are expected to improve the mechanical properties which are consistent with the previous report [10,[13][14][15].…”

“…Recently, CNTs have been widely used as reinforcing materials for metal matrix composites (MMCs). The previous studies indicated the remarkable characteristics of MMCs reinforced with CNTs, such as aluminium [5][6][7], magnesium [8][9][10], copper [11][12] and titanium [13][14][15][16]. Ti and its alloys are also interested as competitive matrix materials because they exhibit high specific strength which is an important factor for weight reduction of the airplane and automotive applications from the viewpoint of energy consumption.…”

Preparation and elevated temperature compressive properties of multi-walled carbon nanotube reinforced Ti composites

“…Kuzumaki et al [16] have demonstrated a large increase in hardness and Young's modulus of CNTs/Ti composites which are made by mechanical mixing and conventional powder metallurgy. Kondoh et al [17] have prepared unbundled CNTs/Ti composites using the zwitterionic surfactant solutions via wet process, and the tensile strength and microvicker's hardness have been remarkably improved. However the elevated temperature compressive properties which are essential to the plastic processing have not been mentioned.…”

Optimizing powder metallurgy methods: Effects of carbon nanotube dispersal mechanisms on mechanical properties of aluminium/carbon nanotube composites

“…[19][20][21][22] However, some of these same studies have shown that CNT bundles are never exfoliated completely into individual tubes using surfactant-assisted dispersion and CNT clusters are introduced into metal matrices. [19][20][21][22] Therefore, it is necessary to compliment surfactantassisted dispersion with ultrasonication steps to further exfoliate CNT aggregates. During the sonication process, rapid cavitation of air bubbles in the aqueous suspension produce shear stresses that create a pulling force 'fraying' the ends of CNT bundles.…”