The Cu/Ti3AlC2 composites were fabricated by pressureless sintering a mixture of Ti3AlC2 and copper powders. Their microstructures and properties were investigated. It was found that the molten Cu accelerating the decomposition of Ti3AlC2, inducing the interfacial exfoliation to generate, and forming a sub-micro-layered structure making up of TiCx layers and Cu-Al alloy layers within a Ti3AlC2 grain. The flexural strength of the composites is reduced with the increase of the volume content of Ti3AlC2 from 50 % to 90 %. The highest flexural strength reaches to as high as 915 MPa. The fracture mode was changed from ductile to brittle with increase in the content of Ti3AlC2. The higher flexural strength can be attributed to a stronger interface bond between TiCx and Cu-Al phase. The electrical resistivity and Vickers hardness of the composites were also measured.

Al/Ti3AlC2 composites containing 50vol% Al were prepared with high purity of polycrystalline Ti3AlC2 and aluminum powders by pressureless-sintering route at temperatures of 700°C~ 800°C The tribological properties of the composites were investigated by sliding the composites block dryly against low carbon steel disk under high sliding speed. Before and after friction test, the morphology and phase analysis were observed by scanning electron microscope (SEM) and X-ray diffraction (XRD), separately. A definite tribo-glazing layer was found over the worn surface of the composite block, which was the results of tribo-chemical oxidation reaction and the cause forming it could be the high frictional temperature and the mechanical catabolism between the surface of Al/Ti3AlC2 and low carbon steel during sliding friction. The effect of Ti3AlC2 on tribological properties of Al/Ti3AlC2 composite and the possible tribo-chemical reaction mechanism on surface layer of Al/Ti3AlC2 were suggested.

Polycrystalline bulk samples of ternary carbide Ti3AlC 2 ceramics were fabricated by reactively hot-pressing a mixture of Ti, Al, and graphite powders with and without Sn additive. The effects of sintering temperature, time and addition of Sn on the purity, mechanical properties and microstructure of Ti3AlC2 were investigated. The result showed that the TiC content was strongly influenced by sintering temperature for the Ti3AlC2 samples without Sn additive, and the most suitable sintering temperature to create the lowest TiC content was 1400°C. The addition of Sn additive led to a distinct decrease in TiC content. The flexural strength of the testing materials had close relation with the TiC content and sintering time. A certain content of TiC second phase and longer sintering time were helpful to improving the flexural strength. The sample sintered at 1400°C for 2 h possessed the highest flexural strength.

The superstructure phenomenon in Ti3Siy-xAlxCz interlayer solid solution ceramics was found and studied. It is showed that in the X-ray diffraction patterns of the interlayer solid solution Ti3Si0.9Al0.3C1.93 and Ti3Si0.8Al0.4C1.93 bulk samples, which were in-situ reactively synthesized by hot-pressing the elemental Ti, Si, Al and C (graphite) mixed powders, the diffraction peaks of [00L] crystal planes are very weak, there is only a small diffraction peak belonging to the [008], and the diffraction peaks belonging to [0021, [004] and [0061 crystal planes almost not exist. However, all diffraction peaks belonging to [00L] crystal planes appear in the x-ray diffraction pattern of the powders taken from the bulk samples. This superstructure phenomenon demonstrates that the Ti3Si0.9Al0.3C1.93 and Ti3Si0.8Al0.4C1.93 bulk samples indeed are random solid solution. Due to the internal stresses releasing, the powders taken from the bulk samples generated a transition from random state to order, consequently the x-ray diffraction patterns of the powders presented stronger [00L] crystal plane diffraction peaks. This superstructure phase-change may take some fundamental effects on performances of the Ti3Si0.9Al0.3C1.93 and Ti3Si0.8Al0.4C1.93 bulk materials.

The current-carrying wear characteristics of Ti3SiC2 and Ti3AlC2, which belong to the ternary carbides, were studied. And the wear mechanisms of Ti3SiC2 class materials with the interaction and coupled action under high-current, thermal stress and friction force were discussed. The tests were carried out using, a block-on-disk type, current-carrying, high speed friction tester, with sliding speeds of 20 m/s, normal pressures range in 0.4 similar to 0.8 MPa, and the current intensity of 0 A, 50 A and 100 A, respectively. The results showed that the Ti3SiC2 class materials showed good current-carrying tribological properties under the appropriate sliding speeds and normal pressures. However, the wear rates of Ti3SiC2 or Ti3AlC2 With current friction were larger than that without current, and increased with the increase of the current intensity. The friction surfaces were observed and analyzed using SEM & EDS. It was found that, the wear rate of the Ti3SiC2 class materials with current friction was composed of two parts: the interaction of micro-arc ablation and mechanical friction, and the coupled action of thermal and mechanical effect. The micro-arc ablation causes the oxidation, melting and decomposition of the friction surface and the crack creating of the subsurface. This induces the changing of the wear property of Ti3SiC2 class materials. The coupled action of the electrothermal effect and the frictional heat also makes the wear property worse. Which one will be the main mechanism: the interaction or the coupled action of mechanical, electrical and thermal, is depended on the material parameters of Ti3SiC2 class as well as the mechanical parameters such as normal pressure and sliding speed.

High purity Ti3Si0.8Al0.4C1.95 layered solid solution ceramic has been fabricated by in-situ hot-pressing from titanium, silicon, aluminum, and graphite elemental powders. The effect of the synthesis temperature to the purity of the product, the phase composition and the microstructure of the product were analyzed, and the density, flexural strength and resistivity were also analyzed. The result indicates that the appropriate temperature for hot-pressing is about 1550 V, but higher or lower temperature will lead to the appearance of the TiC and Ti5Si3; the grains have a typical platelike shape, and layered structure could be seen clearly from the SEM micrograph; the density, flexural strength and resistivity of the Ti3Si0.8Al0.4C1.95 are all between those of pure Ti3SiC2 and Ti3AlC2.

An interformational exfoliation behavior of the layered Ti3AlC2 induced by copper was firstly investigated via a “Cu-Ti3AlC2-Cu” sandwich sample infiltration-sintered at 1100oC to 1200oC. It was found that the molten Cu accelerates Ti3AlC2 to decompose, induces the interformational exfoliation to generate, and consequently forming a sub-micro-layered structure making up of TiC0.67 layers and Cu-Al alloy layers within a Ti3AlC2 grain. This interformational exfoliation behavior can be attributed to a topotactic mechanism due to the outward diffusion of Al the entering of Cu.

Cu/Ti3AlC2 cermets prepared by pressless sintering a mixture of Ti3AlC2 and copper powders were investigated. It was found that the Cu/Ti3AlC2 possesses an unusual microstructure made up of sub-micro-sheet layered Ti3C2 and Cu-Al alloy within one Ti3AlC2 particulate. The fracture strength measured by the three-point-bending manner is increased but the deformation rate is reduced with increase in the volume content of Ti3AlC2 from 30 % to 90 %. The highest fracture strength reached to as higher as 983.9 MPa, corresponding to an extreme strain of 2.64 %. The fracture in mode was changed from brittle to ductile with reduce in the content of Ti3AlC2. The higher fracture strength can be attributed to a stronger interface bond between Ti3AlC2 and Cu-Al phase. A significant network feature formed by the Cu-Al alloy surrounding Ti3AlC2 particulates was observed from the fracture face.

High purity Ti3Al1.2-xSnxC1.8 (x=0 similar to 0.8) solid solutions powders were fabricated using elemental powder mixture as the raw materials by the pressureless sintering. The formative condition and the microstructure of Ti3AlSn0.2C1.8 were investigated via X-ray diffraction (XRD), scanning electron microscope (SEM) in details. The high purity Ti3AlSn0.2C1.8 powders can be fabricated by a pressureless calcining process from titanium, aluminum, tin and graphite powders at the temperatures from 1350 degrees C to 1500 degrees C for 5 min. The SEM analysis indicated that the calcining temperatures have obvious influence on the microstructure. With the increase of the temperature, the grain morphology is changed to plate-like grain. On the basise of the investigation, a series of high purity Ti3Al1.2-xSnxC1.8 (x=0 similar to 0.8) powder were synthesized under the optimized technical condition.

Cu-Ti3AlC2 cermet was fabricated by pressureless sintering power mixtures of Cu and Ti3AlC2. The effect of Cu content on reaction product was studied. The fracture strength, Vickers hardness and conductivity of Cu-Ti3AlC2 were investigated. And the microstructure and fracture face were observed and analyzed. The experimental results showed that, under the proper condition, Ti3AlC2 bulks with high-density were fabricated by pressureless sintering when the content of Cu was in a certain range. Much higher fracture strength and Vickers hardness can be attributed to the special microstructure of Cu-Ti3AlC2.

The tribological behaviors of high pure bulk Ti3SiC2 dry-sliding against a low carbon steel disk were investigated on a block-on-disk type tester under several sliding speeds from 5m/s to 60m/s and normal pressures from 0.1MPa to 0.8MPa. It was found that both the coefficient of friction and the wear rate of Ti3SiC2 were dependent on the presence of a frictional film consisting of oxides of Ti, Si and Fe in the Ti3SiC2 friction surface. The oxide film was formed and the percentage of coverage was increased with increasing the normal pressure for the medium sliding speeds of 20m/s and 40m/s. The oxide film could be formed but was maintained difficultly with increasing the normal pressure when the sliding speed was up to 60m/s. Few of the oxides was generated and hence almost no oxide film was formed in the friction surface when the sliding speed was 5m/s. The presence of the oxide film induced the coefficient of friction to reduce, but made the wear rate of Ti3SiC2 increase. The coefficient of friction and the wear rate (×10−6mm3/Nm) of Ti3SiC2 were of 0.53 and 0.91, 0.26 and 1.35, 0.16 and 2.05, and 0.29 and 3.75 under the normal pressure of 0.8MPa and the sliding speed of 5m/s, 20m/s, 40m/s and 60m/s, respectively.

The argon-arc welding of Cu/Ti3AlSn0.2C1.8 cermet was carried out without filler. The changes of microstructure in welding zone and its vicinity were observed, and flexural strength of the welding zone was also tested. The results show that the joining of Cu/Ti3AlSn0.2C1.8 cermet by argon-arc welding can be performed. The microstructure in welding zone is made up of network-shaped Cu(Ti, Al, Sn) alloys and dispersed TiCx particles. The flexural strength of welding zone at room temperature reaches up to 851 MPa under the conditions of proper arc current density, arc time and pressure. The flexural strength of welding zone reaches or exceeds that of Cu/Ti3AlSn0.2C1.8 cermet.

Al/Ti3SiC2 composite samples were prepared by pressless-sintering route with high purity of polycrystalline Ti3SiC2 and aluminum powders. As yttria Y2O3 being additives during sintering process, the interesting change is that impurities Al4C3, Al4SiC4 and Al3Ti phase which are familiar in products of reactions between Ti3SiC2 and aluminum disappeared and that is valuable to stability of Al/Ti3SiC2 composite in atmosphere due to hydrolyzation of Al4C3. Then the tribological properties of 50Al/ 45Ti3SiC2/5Y2O3 and 50Al/50Ti3SiC2 were investigated by sliding the composites block dryly against low carbon steel disk for the sliding speed 20 m/s and the normal pressure of 0.2~0.8MPa. It was found that with load higher, the friction coefficient of 50Al/45Ti3SiC2/5Y2O3 increased from 0.21 to 0.57 and then reduced to 0.48, which is a little higher than 50Al/50Ti3SiC2 on large scale of pressure except under 0.2 ~ 0.3 MPa, but meanwhile it is remarkable that its rate of wear maintained a nearly steady value about 1.40 × 10-5 mm3/N·m comparing with 50Al/50Ti3SiC2, which shows a valuable tribological properties called non-pressure dependence to frictional materials.

Tribological behaviors and the relevant mechanism of a highly pure polycrystalline bulk Ti3AlC2 sliding dryly against a low carbon steel disk were investigated. The tribological tests were carried out using a block-on-disk type high-speed friction tester, at the sliding speeds of 20–60 m/s under a normal pressure of 0.8 MPa. The results showed that the friction coefficient is as low as 0.1∼0.14 and the wear rate of Ti3AlC2 is only (2.3–2.5) × 10−6 mm3/Nm in the sliding speed range of 20–60 m/s. Such unusual friction and wear properties were confirmed to be dependant dominantly upon the presence of a frictional oxide film consisting of amorphous Ti, Al, and Fe oxides on the friction surfaces. The oxide film is in a fused state during the sliding friction at a fused temperature of 238–324 °C, so it takes a significant self-lubricating effect.

Polycrystalline bulk samples of ternary carbide Ti3AlC2 ceramics were fabricated by reactively hot-pressing a mixture of Ti, Al, and graphite powders with and without Sn additive. The effects of sintering temperature, time and addition of Sn on the purity, mechanical properties and microstructure of Ti3AlC2 were investigated. The result showed that the TiC content was strongly influenced by sintering temperature for the Ti3AlC2 samples without Sn additive, and the most suitable sintering temperature to create the lowest TiC content was 1400°C. The addition of Sn additive led to a distinct decrease in TiC content. The flexural strength of the testing materials had close relation with the TiC content and sintering time. A certain content of TiC second phase and longer sintering time were helpful to improving the flexural strength. The sample sintered at 1400°C for 2 h possessed the highest flexural strength.

The tribological behavior of a new cermet Ti3AlC2/Cu was experimentally investigated. The results showed that the Ti 3AlC2/Cu was a good tribological material sliding against the low carbon steel, especially for a high sliding speed. The friction coefficient was as low as 0.13-0.15, and the Ti3AlC2/Cu wear rate was only 3.4× 10-6 mm3/Nm, for the sliding speed of 60 m/s and the normal pressure of 0.8 MPa. The forming of a frictional film consisted of Ti, Al, Cu and Fe oxides on the friction surfaces could be a fundamental cause.

The tribological behavior of a new cermet Ti3AlC2/Cu was experimentally investigated. The results showed that the Ti3AlC2/Cu was a good tribological material sliding against the low carbon steel, especially for a high sliding speed. The friction coefficient was as low as 0.13 ~ 0.15, and the Ti3AlC2/Cu wear rate was only 3.4×10-6 mm3/Nm, for the sliding speed of 60 m/s and the normal pressure of 0.8 MPa. The forming of a frictional film consisted of Ti, Al, Cu and Fe oxides on the friction surfaces could be a fundamental cause.