The Effect of Hydrogen on an Iron Based Amorphous Alloy
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THE EFFECT OF HYDROGEN ON AN IRON BASED AMORPHOUS ALLOY H. SHAHANI, H. SODERHJELM AND MATS NYGRENx Department of Casting of Metals, The Royal Institute of Technology Stockholm, Sweden, XThe Arrhenius Laboratory, Stockholm, Sweden
ABSTRACT
In this-investigation we have systematically studied the brittleness and the atomic structure in an Fe(SiBC) alloy. Different amounts of hydrogen have been dissolved in the alloy. It has then been studied at different cooling rates. Hydrogen gas of different partial pressures was dissolved into the melt. The alloy was then rapidly quenched by a chill block melt spinning method. The cooling rates were changed by changing the velocity on the chilling roll. The brittleness and the atomic structure were examined by bending tests and x-ray diffraction. X-ray diffractions showed that the ribbons were amorphous when the cooling rate was sufficient. Amorphous ribbons without any hydrogen were ductile, crystalline ribbons of this alloy were brittle. The ribbons with dissolved hydrogen and amorphous structure were brittle even at small amounts of hydrogen. At the highest cooling rates the ribbons with low hydrogen content were ductile. There seems to be a connection between the hydrogen content and the amorphous ribbons ductility. The hydrogen content only has a slight influence to amorphous structure.
INTRODUCTION
Hydrogen easily dissolves in liquid metals. The solubility decreases rapidly when the metal solidifies and with decreasing temperature. Many alloys become brittle even when a small amount of hydrogen is present. In this investigation we have dissolved different amounts of hydrogen in a Fe (Si 5 B1iC4) liquid alloy. Ribbons were then directly cast from the melt by a chill-block melt-spinning method. Both amorphous and crystalline atomic structures were obtained by changing the velocity of the chilling substrate. The hydrogen content, the brittleness and the atomic structure were then examined on the ribbons.
EXPERIMENTAL
The ribbons were made by a single roller melt spinning equipment. The diameter of the copper roll was 159 mm. Three grams of the Fe (SiBC) alloy was used for each experiment and it was melted by a high frequency induction furnace. The crucible was made of quartz; in the crucible bottom there was a hole with a diameter of 0.5 mm. A gas mixture was blown for 30 seconds through a lance onto the top of the liquid alloy.(Fig. 1). The gas mixture was a mixture of hydrogen and argon. The different amounts of hydrogez gas which were used in these experiments were 0, 5, 10, 50 and 100 volume %. The amount of gas was 200 liters per hour. The driving ejection pressure was 100 kPa; argon gas was used (Fig. 2). The distance between the crucible and the copper role was 3 mm and the melt jet inclination was 900. The substrate velocities were 4, 8, 13, 17, 21, 25, 29 and 33 m/s.
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Fig. 1. Gas flow during the gas treatment.
Fig. 2.
Gas flow during casting
The atomic structure was determined by x-ray diffraction, using nickel filtered CuKc radiation. The anount o
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