Shili Shu

Fabrication of TiCx-TiB2/Al Composites for Application as a Heat Sink

Metal matrix composites reinforced with ceramic particles have become the most attractive material in the research and development of new materials for thermal management applications. In this work, 40–60 vol. % TiCx-TiB2/Al composites were successfully fabricated by the method of combustion synthesis and hot press consolidation in an Al-Ti-B4C system. The effect of the TiCx-TiB2 content on the microstructure and compression properties of the composites was investigated. Moreover, the abrasive wear behavior and thermo-physics properties of the TiCx-TiB2/Al composite were studied and compared with the TiCx/Al composite. The compression properties, abrasive wear behavior and thermo-physics properties of the TiCx-TiB2/Al composite are all better than those of the TiCx/Al composite, which confirms that the TiCx-TiB2/Al composite is more appropriate for application as a heat sink.

A Novel Approach of Using Ground CNTs as the Carbon Source to Fabricate Uniformly Distributed Nano-Sized TiCx/2009Al Composites

Nano-sized TiCx/2009Al composites (with 5, 7, and 9 vol% TiCx) were fabricated via the combustion synthesis of the 2009Al-Ti-CNTs system combined with vacuum hot pressing followed by hot extrusion. In the present study, CNTs were used as the carbon source to synthesize nano-sized TiCx particles. An attempt was made to correlate the effect of ground CNTs by milling and the distribution of synthesized nano-sized TiCx particles in 2009Al as well as the tensile properties of nano-sized TiCx/2009Al composites. Microstructure analysis showed that when ground CNTs were used, the synthesized nano-sized TiCx particles dispersed more uniformly in the 2009Al matrix. Moreover, when 2 h-milled CNTs were used, the 5, 7, and 9 vol% nano-sized TiCx/2009Al composites had the highest tensile properties, especially, the 9 vol% nano-sized TiCx/2009Al composites. The results offered a new approach to improve the distribution of in situ nano-sized TiCx particles and tensile properties of composites.

Effects of different carbon sources on the compressive properties of in situ high-volume-fraction TiCx/2009Al composites

Effects of carbon sources, i.e. carbon nanotubes (CNTs), graphite, carbon black (C-black), on synthesised TiCx size, shape and compressive properties of in situ 40–60u2005vol.-% TiCx/2009Al composites were investigated. When CNTs and C-black were used, the synthesised TiCx with particle sizes of 0.08–1 and 0.9–5u2005µm, respectively, was spherical or nearly spherical in shape, while graphite was used, the synthesised TiCx with particles sizes of 0.2–2u2005µm was octahedral or spherical in shape. The yield strength (σ0.2), ultimate compression strength (σUCS) and hardness of TiCx/2009Al composites all increased with increasing TiCx content, while the plastic strain (ε) decreased. The σ0.2, σUCS, ε and hardness of 60u2005vol.-% TiCx/2009Al composites fabricated by using CNTs were 722u2005MPa, 946u2005MPa, 3.2% and 260u2005±u200510u2005Hv, respectively. The strength increase of the composites resulted from finer-sized TiCx particles with spherical shape.

Microstructures and Compressive Properties of Al Matrix Composites Reinforced with Bimodal Hybrid In-Situ Nano-/Micro-Sized TiC Particles

Bimodal hybrid in-situ nano-/micro-size TiC/Al composites were prepared with combustion synthesis of Al-Ti-C system and hot press consolidation. Attempt was made to obtain in-situ bimodal-size TiC particle reinforced dense Al matrix composites by using different carbon sources in the reaction process of hot pressing forming. Microstructure showed that the obtained composites exhibited reasonable bimodal-sized TiC distribution in the matrix and low porosity. With the increasing of the carbon nano tube (CNT) content from 0 to 100 wt. %, the average size of the TiC particles decreases and the compressive strength of the composite increase; while the fracture strain increases first and then decreases. The compressive properties of the bimodal-sized TiC/Al composites, especially the bimodal-sized composite synthesized by Al-Ti-C with 50 wt. % CNTs as carbon source, were improved compared with the composites reinforced with single sized TiC. The strengthening mechanism of the in-situ bimodal-sized particle reinforced aluminum matrix composites was revealed.

Effect of Mn, Fe and Co on the compression strength and ductility of in situ nano-sized TiB2/TiAl composites

The element of Fe can enhance the strength of TiB2/TiAl composite, but it is detrimental to the ductility of the composite due to the existence of large bulk TiB2 phase at grain boundary. The element of Mn is beneficial to the ductility of TiB2/TiAl composite, of which the fracture strain increases from 15.9 to 17.9xa0% with the addition of 2 at.% Mn. The element of Co can improve the strength and ductility of TiB2/TiAl composite simultaneously. With the addition of 2 at.% Co, the ultimate compression strength of TiB2/TiAl composite increases from 1829 to 1906xa0MPa and the fracture strain increases from 15.9 to 17.2xa0%.