| NCu30-4-2-1 alloy in addition to the ordinary monel alloy corrosion resistance, as well as high strength and hardness, and good wear resistance, and was used in the manufacture of jet fuel and other precision friction parts. In this thesis, the influence of working methods and heat treatment condition on the microstructure and hardness of NCu30-4-2-1 alloy was investigated by X-ray diffraction, optical microscopy, SEM, Vickers hardness tests and EDS tests. NCu30-4-2-1 alloy after aging were studied to observe corrosion of precipitated phase method and heat treatment on the NCu30-4-2-1 alloy microstructure and mechanical properties of impact. Infer that the strengthening mechanism of alloy, and the hardness method combined with the JMA equation, studied NCu30-4-2-1 alloy isothermal aging kinetics of phase transition.The main contents were as follows:(1) Metallographic etch can use 1g ammonium sulfate, 3g Citric acid and 100 ml water as the electrolyte. The corrosion condition is under the current density of 0.04 A/cm2 for 40 s. Then the NCu30-4-2-1 alloy precipitated phase can be observed by the present emission scanning electron microscopy(SEM).(2) Although NCu30-4-2-1 alloy at 950℃ solution heat 4 hours, there is very little β-Ni3 Si phased particles, but in the same aging condition, there was no significant difference that the aging precipitation phase morphology, size and quantity compared to these complete solid solution alloy specimens with higher temperatures. At the same time, due to the relatively low solid solution temperature, the alloy grain will be smaller and the quantity of twin will be more. The grain size is under the solid solution temperature of 1000 ℃ and 1050 ℃.So the solution at 950 ℃ heat preservation 4 hours, the sample vickers hardness value after aging treatment is higher. The fine crystal reinforcing can strengthen the alloy.(3) NCu30-4-2-1 alloy aging treatment at 500℃ to 650℃ after 950 ℃ solution incubated for 4 hours, the precipitates ?′-Ni3 Si evenly distributed in the grain interior, and with the aging temperature, precipitation phase ?′-Ni3 Si fine particles gradually become more uniform. Alloy at 500℃ to 650℃ aging process, with the increase of aging temperature, alloy vickers hardness value increased gradually. Under the same aging temperature, with the increase of aging time, alloy hardness fell slightly after rose first, finally the hardness of alloy basic remain unchanged. And it can infer that the NCu30-4-2-1 alloy ageing strengthening is the result of Orowan mechanism and cutting mechanism joint action, the Orowan mechanism is the main strengthening mechanism.(4) According to NCu30-4-2-1 alloy isothermal aging hardness value under different temperature and the JMA equation, it calculated the Avrami index n and k values under the different temperatures. To deduced the phase transformation kinetics equations of the alloy under different test temperatures. Calculated the activation energy of the NCu30-4-2-1 alloy phase transition E=42.45KJ/mol. Binding reaction mechanism equation, it reveals that the reaction mechanism of NCu30-4-2-1 alloy at500℃ to 650℃ isothermal aging process is a three-dimensional diffusion.(5) According to the hardness of alloy that can calculate the TTT diagram of NCu30-4-2-1 alloy at 500℃ to 650℃. Combined with ?′-Ni3 Si phase in the law of precipitation of 500℃ to 650℃ and diffusion type phase change law of homogeneous nucleation It can be inferred that the temperature is around 650℃ which is the fastest aging precipitation rate of ?′-Ni3 Si phase, and the precipitation of ?′-Ni3 Si phase is located in the lower part of the "C" curve Ni3 Si phase In the temperature range from 500℃ to 650℃. |
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