| MoSi2 and MoSi2 matrix composites had been successfully prepared by means of mechanical alloying, heat treatment, IP and high-temperature sintering technique. Their room-temperature mechanical properties and low-temperature oxidation properties were determined by Vickers indentation and TGA, respectively. Using an MM-200 type tester measured their friction and wear properties under different conditions. The microstructure, surface micrograph and phase formation were investigated by means of SEM, microprobe, X-ray and TEM. Results are as following:1. SHS (Self-propagating High-temperature Synthesis) and diffusion solution are two kinds of formation mechanisms of MoSi2 by mechanical alloying at different milling conditions. The milling energy area what they need was accurately limited by using a Magini-Iasonna mode for the first time. Effects of milling parameters and charging volume on the phase formation in milling process were discussed through the energy maps. It shows that when the effective extensive factory above 1.06 J/g s, the forrmition mechanism of MoSi2 by mechanical alloying is SHS. Otherwise, when it is below 0.917 J/g-s, the formation mechanism of MoSi2 is diffusion solution. The total milling energy required for the beginning of crystalline M0S12 phase formation by SHS or diffusion solution are 24kJ/g and 114kJ/g, respectively. Charging volume should be limited in the rage of two third of volume of vial, or else, it will rapidly decrease the milling efficiency.2. The sintering properly of M0S12 synthesized by SHS and mechanical alloying, and the influence of rare-earth on it were investigated. Effects of mechanical activated sintering and rare earth activation sintering on MoSi2 were analyzed on the basis of a method by German et al.3. The trait of phase formation of Al-Mo-Si and W-Mo-Si systems during high energy milling process was observed in detail. The feasible preparation technology of AI/M0S12 and WSi2/MoSi2 composites was put forward. Results show that adding 8.5at.%Al and 50mol.%WSi2 could obviously strengthen and toughen MoSi2 material, respectively. The main strengthening mechanisms in MoSi2 matrix composites are fine grain strengthening, solid solution strengthening, the second phase particles strengthening. The main toughening mechanisms in Al/MoSi2composite are fine grain toughening, crack deflection and microbridging toughening, but to WSi2/MoSi2 composite, they are fine grain toughening, grain drawing toughening, and crack deflection, microbridging and bowing toughening.4. On the basis of thermodynamics and dynamics theory, the chemical-stability graph of oxide of MoSi2 ar.d the kinetics of oxidation of MoSi2 at low-temperature were founded. All these can be used to explain the relation of oxide to temperature and oxygen-pressure, and the relation of low-temperature oxidation property to microstructure of MoSi2 The kinetic reason that the very poor oxidation resistance of MoSi2 at about :500C is disclosed for the first time to be because of the maximum reaction constant. The low-temperature oxidation resistibility of MoSi2 material is clearly weakened by the addition of Al and WS12. And the reason resulting in PEST phenomenon is analyzed.5. The wear mechanisms of MoSi2 material against alloy steel under dry friction and oil lubrication, and against itself under dry friction condition were systematically investigated. Effects of the second phase, such as Al, WSi2 and rare-earth et al, on the dry friction and wear properties of MoSi2 matrix were also observed. As a result, MoSi2 and MoSi2 matrix composites have excellent wear resistibility. The wear mechanisms such as plastic deforming, fatigue fracture, oxidation, adherence and abrasive wear, are found in MoSi2 and MoSi2 matrix composites. By linear regression, the relation of friction coefficient, u., or wear rate, W, to load, P, can be described as u = a + bp + cp2 +dp3 +ep4 or W = a + bp + cp2 +dp3 + ep4 . The abrasive wear properties of MoSi2, MosSi3/MoSi2 and rare-earth/MoSi2...
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