Dongtao Jiang

Electrically Conductive and Wear Resistant Si3N4-Based Composites with TiC0.5N0.5 Particles for Electrical Discharge Machining

Electrically conductive and wear resistant Si3N4-based composites were developed in order to facilitate electrical discharge machining (EDM). The microstructural and mechanical properties of Si3N4-based composites with different amounts of TiC0.5N0.5, fabricated by hot pressing at 1650°C for 1 hour, are investigated and evaluated. The hardness of the micron-sized TiC0.5N0.5 powder based composites increased with increasing TiC0.5N0.5 content from 20 up to 40 vol. %, whereas the bending strength decreased. The fracture toughness reached a maximum at 30 vol. % TiC0.5N0.5 and exhibits a strong anisotropy with respect to the hot-pressing direction. The EDM behaviour of the composites is strongly influenced by the TiC0.5N0.5 content. The composites with a higher TiC0.5N0.5 content have a lower material removal rate but a better surface quality.

Superplasticity of ceramic particulate reinforced magnesium alloy composite made by a vortex method

High Strain Rate Superplasticity (HSRS) in metal matrix composites offers an efficiently near-net shape forming method to automobile, aerospace industries. HSRS materials usually exhibit an elongation of 250-600% at a high strain rate of about 10 -1 ∼10 s -1 . The purpose of this study is to develop a thermomechanical processing route to produce a fine microstructure and to further produce HSRS in a ceramic particulate reinforced Mg alloy composite fabricated by a vortex method. The superplastic behavior at high strain rate was observed a TiC/Mg-5wt%Zn and TiC/ZK51Mg composite, fabricated by a vortex method, extrusion, and hot-rolling. The strain rate sensitivity (m value) of the composites is about 0.3∼0.4. TiC/Mg-5wt%Zn exhibits the total elongation of 340% at strain rates 0.067s -1 at 743K, although the hot-rolled TiC/ZK51 Mg composite indicates total elongation of 100% at a strain rates of 0.5x10 -1 S - 1 at 673∼713K.

Processing of a Graded Ceramic Cutting Tool in the Al2O3-ZrO2-Ti(C,N) System by Electrophoretic Deposition

In this study, the development of a functionally graded material (FGM) with hard outer surfaces and a tougher inner core was envisaged. The applicability of electrophoretic deposition (EPD) for the processing of FGM materials by continuously changing the suspension composition is shown. Optimisation of the colloidal processing technique was combined with hot pressing experiments on homogeneous composites in the Al2O3-ZrO2-Ti(C,N) system in order to create a very hard functionally graded material with beneficial residual stresses. Finally, the residual stress distribution was briefly discussed using an existing analytical model.

Microstructure and mechanical properties of spark plasma sintered ZrO2-Al2O3-TiC0.5N0.5 nanocomposites

Future materials for wear resistant components require a combination of excellent mechanical properties such as hardness and toughness, short processing times and good electrical conductivity to facilitate shaping by electro discharge machining (EDM). In this work, the hardness and fracture toughness of t-ZrO2 based electro conductive composites was optimised, while short processing times below 20 minutes using spark plasma sintering were sufficient to obtain near fully dense materials. The influence of powder processing technique using TiC0.5N0.5 as the starting powder and yttria as a stabiliser on the mechanical properties of ZrO2-TiC0.5N0.5-Al2O3 based composites was investigated. Fully dense Y-TZP based composites possessed an excellent toughness of 9.2 MPa.m1/2 and an increased Vickers hardness of 1397 kg/mm².

High Strain Rate Superplasticity of a Powder Metallurgy Pure Aluminum 1N90

Superplastic characteristics of 1 N90 pure PM aluminum and the microstructure evolution are investigated to make clear deformation mechanism of the High Strain Rate Superplastcity(HSRS). The 1N90 exhibits the m value of about 0.47 and the total elongation about 500% at the strain rate of 1.2x10 -2 s -1 and 893K. The 1N90 shows grain size of 10∼20 μm with the subgrains of 1∼2 μm after hot rolling at above 773K. ()n the other hand, 99.99% pure aluminum by squeese casting shows the total elongation less than 100% and m=0.2 and has a grain size of above 100 μm after hot rolling.