Study On Fabricating Of Aluminum Matrix Composites Reinforced By In-Situ Synthesized Al-Ti Intermetallics

The issue on energy will be an important issue to be faced. The reserves of aluminum is up for metal resources, which is widely used in construction, high-speed trains aerospace and so on, And it is the first choice for lightening.The development of aluminum matrix composites has the important meaning, its performance is similar to certain low-carbon alloyed steel's. The situation reduces use and relieves dependence for ferrous metal. So the composites' preparation becomes very important. The reinforcing phases generated by in-situ synthesis technology are fine, having good wettability with matrix, which the applied reinforcing phases do not possess. And the interface between it and matrix is not polluted. But there are some problem, for example, the limitation of its volume fraction in the matrix, complicated technology and high cost. It is a bottleneck for the composites of further development and application. This topic used the stirring in-situ synthesis technology to prepare TiAl3/7075 composites. The density of in-situ synthetical TiAl3 phase is near the matrix, Its wettability is good with the matrix, And it has almost the same thermal expansion rate with the matrix. This topic used adding yttrium and ultrasonic treatment in order to increase the content of titanium in the matrix, improve the properties of materials greatly and provide some idea for enlarging the use of composites. The content of research are as follow:The best material added with reaction were defined through thermodynamic analysis and experimental phenomena. The author established the kinetic model of reaction system, deduced the kinetic equation, analyzed the factors which influences the rate of reaction. The factors were the initiative size of Ti particle, the boundary layer's thickness, the diffusion coefficient, the temperature of system.The relation between different Ti content and the composites's microstructure and property were studied. Stirring and holding time effecting the TiAl3's morphology and distribution were analyzed, And the relation between the TiAl3's morphology and Ti content. The TiAl3 phase's formation mechanism and influencing factors were analyzed. The chang law of the property of composites was discussed. The influence of rare earth yttrium on composites's microstructure was studied. The author found that rare earth yttrium effected the size of matrix grain, the TiAl3's morphology and distribution and analyzed the reason on this phenomenon, finally determined the best content of RE addition to the matrix and composites.Ultrasonic treatment producing an effect on the microstructure and property of the matrix and composites was studied. The effect of time, rate and way of ultrasonic work on the matrix's microstructure was analyzed The technology of prepareing composites had been determined, which contains the mass fraction of yttrium from one to six, And the relation between ultrasonic treatment and the change of TiAl3's morphology was analzyed.