The temperature dependence of surface tension and density for Fe-Cr-Mo (AISI 4142), Fe-Cr-Ni (AISI 304), and Fe-Cr-Mn-Ni TRIP/TWIP high-manganese (16 wt% Cr, 7 wt% Mn, and 3-9 wt% Ni) liquid alloys are investigated using the conventional maximum bubble pressure (MBP) and sessile drop (SD) methods. In addition, the surface tension of liquid steel is measured using the oscillating droplet method on electromagnetically levitated (EML) liquid droplets at the German Aerospace Centre (DLR, Cologne). The data of thermophysical properties for Fe-Cr-Mn-Ni is of major importance for modeling of infiltration and gas atomization processes in the prototyping of a ''TRIP-Matrix-Composite.'' The surface tension of TRIP/TWIP steel increased with an increase in temperature in MBP as well as in SD measurement. The manganese evaporation with the conventional measurement methods is not significantly high within the experiments (D Mn \ 0.5 %). The temperature coefficient of surface tension (dr/dT) is positive for liquid steel samples, which can be explained by the concentration of surface active elements. A slight influence of nickel on the surface tension of Fe-Cr-Mn-Ni steel was experimentally observed where r is decreased with increasing nickel content. EML measurement of high-manganese steel, however, is limited to the undercooling state of the liquid steel. The manganese evaporation strongly increased in excess of the liquidus temperature in levitation measurements and a mass loss of droplet of 5 % was observed.

The aim of the current research is the experimental investigation of the mass median particle size d 50 as a function of surface tension for liquid Cr-Mn-Ni steel alloy with 16% Cr, 7% Mn, and 9% Ni. To modify the liquid steel design sulfur was add to the Cr-Mn-Ni steel in five steps up to a 1000 mass ppm. The surface tension of the liquid steel alloy was measured using maximum bubble pressure method and yttria stabilized capillary in a temperature range from 1701 to 1881 K. In addition, the same steel charges were sprayed to steel powder using a vacuum inert gas atomization using pure argon gas. The increase of sulfur in Cr-Mn-Ni steel will decrease the surface tension to 0.91 N m À1 . The temperature coefficient of surface tension is positive for all investigated Cr-Mn-Ni alloys due to a sulfur content !100 mass ppm. The final mass median particle size d 50 decreases from 54.3 mm for AISI 304 reference steel alloy to 17.1 mm for Cr-Mn-Ni steel alloy (16-7-9 S10) with the highest sulfur content and the lowest surface tension of all investigated liquid steels. It is concluded from the present work that surface tension is the decisive factor in adjusting d 50 at a constant spraying parameters.

In the last years new Cr‐Mn‐Ni‐TRIP/TWIP steels have been developed at the Institute of Iron and Steel Technology, Freiberg University of Mining and Technology. Within the Collaborative Research Center SFB 799, the ZrO2‐ceramic‐TRIP‐steel composite materials are produced using the infiltration of open foam ceramics with liquid steel and using powder metallurgy with small additions of ceramic powder before sintering. The thermophysical properties of liquid steel play an important role in both production routes. They affect the infiltration efficiency in one process and the produced powder size in the other, and therefore finally determine the composite properties. In this work some of these properties were estimated, as they are not available in literature. The investigated steels contain approximately 16% chrome, 7% manganese and 3% to 9% nickel. The surface tension was estimated using two methods: the drop weight method and the maximum bubble pressure method. In the drop weight method similar conditions at the gas/metal interface exist as during the atomization or the infiltration process, where liquid metal is exposed to high volume of inert gas. In all these cases the evaporation of manganese affects the surface tension. For comparison of results and for estimation of the liquid steel density the maximum bubble pressure method was used where the evaporation of manganese is limited. The wettability on partially MgO‐stabilized ZrO2 ceramic substrates and its change with contact time was determined using the sessile drop method.

The thermophysical properties of liquid Cr‐Mn‐Ni steel alloys (16 wt% Cr, 7 wt% Mn, and 3–9 wt% Ni) are investigated using the maximum bubble pressure method in which the manganese evaporation and change in chemical composition is very low after experimental trial. The surface tension of copper was measured as reference and experimental σ is in the range of literature values. It is shown that for AISI 304 austenitic steel the surface tension decreased by an increase of oxygen concentration in steel composition. For Cr‐Ni and Cr‐Mn‐Ni steels, the temperature coefficient dσtrue/dT is positive which is explained by sulfur steel concentrations larger 50 mass ppm. A slight influence of nickel to the surface tension of Cr‐Mn‐Ni steels was experimentally observed where σ was lowered by rising weight percentage of nickel.

In the present work the influence of phosphor on the flowability, the effect on the infiltration of ZrO 2 open foam ceramics and the martensite formation as well as the resulting mechanical properties of high alloyed Cr-Mn-Ni as-cast steels is studied. Additionally, the effect of phosphor on surface tension is investigated. The study is performed using thermodynamic calculations, static tensile tests, notch-bar impact tests, optical light microscopy, scanning electron microscopy, energy dispersive X-ray analysis, electron backscatter diffraction, and the magnetic scale for the detection of ferromagnetic phase fractions. Maximum bubble pressure method is used to measure the surface tension of the liquid steel. The martensite phase fraction is not significantly influenced with increasing phosphor content. The flowability and the quality of the infiltration of open foam ceramics are improved with increasing phosphor contents. The investigated specimens show an increasing yield and an ultimate tensile strength with higher phosphor contents. The uniform and the fracture elongation as well as the notch impact resistance remain at high values. Moreover, an increase in phosphor content did not significantly change the surface tension of the investigated CrMnNi alloys.

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The determination of viscosity of liquid Cr–Mn–Ni steel (16% Cr, 7% Mn) alloyed with 3–20% nickel is of interest in the present experimental investigation. The alloys are manufactured using a cold crucible induction levitation melting. The viscosity measurement is performed using a vibrating finger viscometer for high temperatures (≥1500 °C) and viscosities below 10 mPa s. The BN–ZrO2 vibrating finger is set in a driven harmonic oscillation in its resonance frequency of ca. 26 Hz. The constant peak‐to‐peak amplitude of the oscillator is controlled using a laser micrometer and a powered field coil. The viscosity of Fe–Cr–Mn–Ni alloys is slightly decreased from 3 to 6% nickel and from 6 to 9% nickel a slight increase of the isothermal viscosity is observed. Finally, the viscosity decreased significantly from 9 to 20% nickel content in the samples. The variation in the viscosity at high temperatures can be caused by a change in the primary solidification behavior, as shown in the phase diagram of the Cr–Mn–Ni steel. The temperature function of the viscosity of the high‐alloyed steels is expressed using the Arrhenius function. A precise viscosity measurement is necessary for a mathematical modeling of the vacuum inert gas atomization of steel powder manufacturing.

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