| In the SparkPlasma Sintering,Joule heating and plasma are two main sintering mechanism.In this paper, by experimental measurement and theoretical calculation, we analysingtheregulation of Joule heating sintering mechanism.On the basis of discharge plasma physics, we assemble CaF2 inorganic nanometer spark plasma sinteringaid onthe Fe-6.5Si magnetic powder surface,researching the CaF2 help burning behavior to the magnetic powder.Discharge plasma sintering mechanism analysis and sintering process parameters on the effect of sintering is the emphasis in this study.Using SPS technology under 40 MPa and 550 MPa sintering pressure sintering Fe-6.5Si magnetic powder.According to the date from SPS device real-time record the current and voltage during sintering, we calculate the observational resistance.The resistance value of the powder, pressure head and graphite foil in the die are calculated, and the calculated results are compared with the observed results.Designing the data acquisition card outer of SPS equipment, collecting the pulse voltage in the sintering process in real time, we calculate the relationship between the sintering temperature, resistivity and relative density under different sintering pressure. It is found that the resistance of the circuit mainly comes from the graphite foil and the head during the low pressure sintering process.Using dry milling and wet milling process, we research the relationship between ball mill time and particle size, preparation of the CaF2 inorganic nano powder with average particle size about 10~30 nm.The CaF2 inorganic nano powder was evenly assembled on the outer surface of the magnetic powder by using the alcohol wet packing technology. Byusing automatically and manually sintering methods, under 40 MPa and 600 MPa sintering pressure, wemake use of the CaF2 inorganic nano powder as the spark plasma sintering aid sinteringthe good conductivity of Fe-6.5Si alloy. The inorganic nano powder content and coating effect on surface discharge gap control anddischarge effect in conductor particles was studiedunder 600 MPa pressure.Through controling proper parameters of the SPS process, sampling in the middle stage of sintering, the powder sample surface microstrurcture changes were observed by SEM,we ansys the CaF2 burning effectonFe-6.5Si powder sintering and explore thecoordination mechanismof SPS parameters and inorganic nano discharging enhancement effect.Under the same sintering conditions, in contrast to the pure Fe-6.5Si micron powder sintering, with add CaF2 sintering aidwhich the mass fraction is 0.5%, the sample which initial sintering temperature and final sintering temperature were reduced by 75℃and 70℃, we preparethe samples with relative density 99.1% under the situation of sintering temperaturereducing 60℃. The experimental results show that the smaller Joule heat can achieve a higher density.And the enhancement effect of CaF2 inorganic nano powder is confirmed. At the sintering temperature of 320℃, the partial melting phenomenon was found on the surface of Fe-6.5Si micron powder sintered with CaF2 inorganic nano spark plasma sintering aids.The Fe-6.5Si micro powder with CaF2 inorganic nano spark plasma sintering aids containing 0.5%was sintered under 400 MPa, 500 MPa and 600 MPa, respectively. The coordination mechanism of sintering pressure with sintering aids was studied. With CaF2 inorganic nano aids containing 0.5%, the soft magnetic properties of Fe-6.5Si bulkisincreasedunder540 ℃. Compared with the pure Fe-6.5Si sintering, the saturation magnetic induction increased from 1.72 Tto 2.06 T, and the resistivity increased more than two times. |
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