Papers by Author: Hong Liang Sun

Abstract: The effect of different aluminum content on peritectic reaction and mechanical properties of pentatomic TiAl-based alloy was investigated. The results indicate that the grain size gradually increase with increasing content of aluminum and addition 45.7% aluminum in TiAl-based alloy results in that the peritectic reaction can increase grain size greatly, respectively. The content of aluminum can increase the room temperature strength, high temperature strength but peritectic reaction can effectively reduce tensile strength. Aluminum content has a little effect on the ductility. The stress rupture life has positive correlation relationship with the content of aluminum.

Abstract: Particles reinforced Al-xwt.%Si-Al₂O₃ (x=10,20) composites are fabricated through in situ reaction sintering of Al and SiO₂ powder by hot isostatic pressing. Outgassing process and the microstructure of composites under different sintering processes are studied.XRD analysis confirms that the best hot outgassing temperature is 500°C,in situ reaction achieves completely and samples A2 and B2 have better microstructure at 550°C then heating-up to 700°C only for 1h.The microstructure analysis indicates that the reinforcement particulates distribute uniformly in the aluminum matrix.The mechanical properties test results show that the tensile strength of A2 is higher than B2. when x=10,the Al-Si-Al₂O₃ composites have better performance.

Abstract: Fully dense Ti3SiC2-64vol.%SiC(0.5m) composite materials are successfully fabricated by in situ synthesis under hot isostatic pressing. The high temperature flexure, tension and creep of Ti3SiC2-SiC composites were studied, and the results indicated that the composite had a high tensile strength under high temperature. Above 1000°C the composite were displayed a good high temperature plastic. The creep behavior is characterized by two regimes: an initial transient regime, where έ(dε/dt) decreases with t (time); a secondary creep regime in which έ is more or less constant with time.

Abstract: Fully dense samples of TiB2-TiCX and TiB2-TiCX/15SiC ceramic composites were fabricated by in-situ synthesis under hot isostatic pressing from TiH2, B4C and SiC powders. Their oxidized behaviors at different temperatures were tested. Optical micrograph studies and thermo-gravimetric analyses show that the highest effective temperature of oxidation resistance is 700°C for TiB2-TiCX, and 1100°C for TiB2-TiCX/15SiC. The weight gain of TiB2-TiCX/15SiC below 1100°C is quite low, and it rises up suddenly when the temperature reaches 1200°C. Thus, the highest effective temperature of oxidation resistance is 1100°C for TiB2-TiCX/15SiC. The oxidation dynamic curves of TiB2-TiCX/15SiC ceramics accord with the parabola’s law. The activation energy of TiB2-TiCx/15SiC (189.87kJ.mol-1) is higher than that of TiB2-TiCx (96.44kJ.mol-1). In the oxidation process of TiB2-TiCx/15SiC, TiB2 reacts with oxygen and generates TiO2 and B2O3 at first. A layer of whole homogeneous oxide film cannot be formed, in the mean time, the oxidation of TiC begins. When temperature goes up to 1000°C, TiC phase is totally oxidized. SiC is oxidized to SiO2 at about 900°C, Meanwhile, TiO2 forms denser film than B2O3, which grows and covers the surface of the material, and gives better property of oxidation resistance.

Abstract: TiB2-TiC ceramic matrix composites were fabricated by in situ synthesis under hot isostatic pressing (HIP) with 3TiH2-B4C and 11TiH2-3B4C being the raw materials, respectively. The XRD analysis indicates that the samples synthesized from 3TiH2-B4C have TiB2 and TiC phases, while those from 11TiH2-3B4C have not only TiB2 and TiCx phases, but also Ti3B4 phase. TiB2-TiCx ceramic matrix composites obtained from 11TiH2-3B4C have better mechanical properties than those from 3TiH2-B4C. The microstructures of the composites are investigated with SEM and TEM. TiB2 grains are platelet grains; Ti3B4 grains have two different morphologies. Ti3B4 phases are formed through two different paths: fine grain Ti3B4 is formed through TiB+B=Ti3B4 at low temperature; large plate-like grain Ti3B4 is formed through TiB2+TiB=Ti3B4 at high temperature.