Strengthening of Vanadium Alloys by the Internal Oxidation Process(Metallurgy)

概要

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Fundamental experiments on the internal oxidation process of vanadium alloys, were carried out for the improvement of high temperature strength of the alloys, and the following results were obtained : (1) Zirconium and silicon were alloyed to vanadium, respectively, as an internally-oxidizing element. The former element was more favorable than the latter from the point of view of high temperature strength. (2) Excess of oxygen, supplied by decomposition of NiO, increased the amount of oxygen dissolved in solid-solution in the internally-oxidized alloys, which caused strengthening of the alloys not at high temperature but at low temperature, accompanied by brittlement. (3) Optimum zirconium contents of internally-oxidized V-Zr alloys was in the range of 0.3 and 1.0 wt%. (4) Strength of V-Zr alloys internally oxidized at a temperature above 980℃ was greater than those internally oxidized below this temperature. This fact was attributed to the volume expansion of ZrO_2 due to the β-α transformation when the alloy was cooled down through the transformation points of 980 to 1100℃. (5) Zirconium oxide particles formed by internal oxidation were appreciably stable at temperature around 1000℃, but they grew obeying Seybolt's law at 1300℃ and then dissolved into the matrix above 1500℃.
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