Microstructure And Properties Of Some Nickel Alloy And Sputtering Targets

Due to the numerous excellent properties, nickel alloy bulks and films have wide technical applications. The quality of sputtering target affects the quality of sputtering film directly. In order to get high quality target materials, thin films and special alloys, the research and development must be carried out at digital level. In this thesis, the solidification process of some binary and ternary nickel alloys were simulated based on the CALPHAD method. Since the traditional phase diagram and thermodynamic method cannot calculate out the site occupying fractions of alloying elements in defferent sublattices correctly, the sublattice models based on the strict crystallography structure information were employed for some typical Ni-based intermetallics, the site fractions and ordering behaviours of intermetalllics were predicted by combining first-principles calculations with thermodynamics computations. A suit of automatic program scripts was written, which are used for calculation task generation, calculation task management of masses end-member compounds, as well as data extraction, data checkout and thermodynamic database establishment for the huge numbers of end-members in different prototype structures.The site occupied ordering behavior of some Ni-Cr system intermetallic compounds were reported for the first time. The elastic modulus, shear modulus, Young’s modulus and Poisson’s ratio of CrNi-L10, Cr3Ni-Ll2, Cr3Ni-D022 were calculated by building supercells based on the predicted fine microstructure before. NiCr, Ni4Cr, NiCr4, NiCrFe, and Ni7Mn33 alloy were prepared by using the vacuum induction levitation melting method. Some clear and homogeneous alloy ingots were obtained. The heat treatment processes of alloys were fulfilled based on phase diagram analysis. The phase structure, phase transition and microstructure characteristics of Ni-Cr system alloy were studied systematically, and a series of binary and ternary nickel alloy targets with high quality were obtained. The magnetron sputtering process parameters were studied based on self-made target materials.The results show that the site occupying behaviour of atoms in stoichiometric Cr3Ni is ordered constantly below 800 K, Cr atoms occupy 3c sublattices, while Ni atoms occupy 1a sublattices. When the temperature rises beyond 800 K, alloys show weak disordering trendency. The site preference of different transition metals is from case to case, the more structure similar in periodic table with the matrix elements, the more site preference similar with the matrix elements (structure similar lead site compatibility). Some diversities exist in site preferences which depend on the heat treatment temperature and the types of different elements, and temperature appears strong influence on the site preferences of some elements. CrNi phase with Ll0 structure is brittle material, while Cr3Ni phase with L12 structure and D022 structure are ductile materials.The microstructure and local composition of Ni-Cr system alloys are very sensitive to heat treatment process. The appropriate homogenization heat treatment temperature is between 1200℃-1300℃ when the element content of Ni atoms is between 20%-70%. The main crystalline phase of the NiCr alloy is FCC plus BCC eutectic phase; while the main crystalline phases of Ni4Cr、NiCrFe and Ni7Mn3 alloys are FCC phases, and a little BCC phase precipitates at low temperature; while the main crystalline phase of NiCr4 alloy is BCC phase, and a little FCC phaseprecipitates at low temperature. The microstructure of NiCr4 alloy has serious composition segregation. NiCrFe and Ni7Mn3 alloys are nonsensitive to heat treatment temperature (i.e., thermo-stable). The composition homogeneities of different phases in Ni-Cr alloy are relatively good after heat treatment, which meet the requirements of uniformity of microscopic component in target material with high quality.The results from microhardness tests show that afterhomogenizing annealing heat treatment, the hardness of alloys decrease except Ni4Cr alloy. The hardness of NiCr4 alloy is higher, the hardness are 634.1 HV and 476.7 HV for as-cast and after heat treatment, respectively. The corrosion resistance ability of alloys after heat-treatment is very strong, in addition to Ni7Mn3 alloy, comprehensive ablity of corrosion resistance of other alloys is superior to 304 stainless steel. In 0.5 mol/L H2SO4 solution, the corrosion currents of NiCr, Ni4Cr, NiCr4, NiCrFe and Ni7Mn3 alloy are at least 50% lower than that of 304 stainless steel (2.35×10-5 A/cm2), and the corrosion potentials are at least 30% higher than 304 stainless steel (-0.425V), respectively. There are similar tendencies in 1 mol/L NaCl solution. The optimal magnetron sputtering process conditions for NiCr alloy target are:sputtering power is 160 W, vacuum is 7×10-4 Pa, airflow is 40 mms, sputtering pressure is 0.5 Pa, sputtering time is between 10-20 minutes, distance between target and substrate is 6 cm; for Ni7Mn3 alloy target, sputtering power should be decreased to 100 W.