Study On The Structure And Property Of High Temperature Ni₃Si Based Ordered Alloys

High temperature Intermetallic compounds possess many attractive properties for potential high temperature applications. Ni-Si system high temperature intermetallics (or high temperature order alloys) , in particular, is valued and researched as a new and potential high temperature structure and function material because the distinct and exceptional strength-temperature (or R characteristic) and good corrosion resistance. At the same time, the higher brittleness at room temperature and lower strength at high temperature always were the focus of study.The majour work of this study is the preparation of 3Ni/Si powders, block and composite using the technology of high-energy ball milling, hot-pressing sintering and arc melting respectively. The microstructure and property of the test materials were measured, and the relationship among them was analyzed by theory and discussed primarily. The new opinions as follows were obtained:(1) Phase and microstructure of 3Ni/Si blended powder mixtures in ball milling have been studied by means of Scanning Electron Microscope (SEM) and X-Ray Diffractometer (XRD). It was found that intermetallic compounds of Ni₃₁Si₁₂, was formed after 1h ball milling. As the milling time increasing, the compounds increased and then decreased. The blended powders were changed to amorphous gradually. The new diffraction peaks which were similar to the diffraction peaks of Ni were formed after 45h ball milling. The powders annealed at 900℃ and formed the intermetallic Ni₃Si. The compound of Ni₃₁Si₁₂ was taken as a metastable phsed by the Miedema's semi-empirical theory thermodynamic analysis and the crystal structure analysis. The author put forword an idea of Ni₃Si disorder compound of the powders after 75h milling time in this article, this was different from the opinion of the results powders were supersaturated solid solution.(2) The block of Ni₃Si was prepared when the blended powders of ball milling were sintered by hot-pressing sintering at 1100℃. The results show that the sample displayed fine exquiaxed grain morphology in metallurgical graphs. The hardness of the block was about 608.8 HV, furthermore, there wasn't cracking on the sample under the weight of 30 and 60 kilogram. This result showed that plasticity of the block is well relatively. Besides, the exellent corrosion H₂SO₄ resistance at elevated temperature was found in this study.(3) The microstructures of Ni₃Si based eutectic alloys by arc melting were studied. It was shown that Ni₃Si based eutectic alloy with regular and amorphous laminar morphology can be obtained by means of this way. It was found that Si content was affected the morphology of the alloys greatly. The microstructure displayed the typical morphology of hypoeutectic, eutectic and hypereutectic alloy respectively because of the different Si content. For the hardness of the eutectic alloy was between α-Ni and Ni₃Si phase, it was possible to toughen intermetallic Ni₃Si by means of arc melting.