Abstract
In order to find the properties of the ternary alloys of iron and boron containing Si, Ti, V, Cr, Mn, Ni, Zr, Nb, Mo and W free from carbon, investigation have been made on the peritectoid reaction, microstructure, hardness, tempering properties, hardenability and mechanical properties. The boron contents in the specimens were 0.02% and 0.20%, and the alloying elements were added in consideration of the stoichimetric metal/boron ratio. The results are summerized as follows:
(1) Zr, Ti, Mo and Nb rose the peritectoid reaction temperature of Fe-B alloy, but Cr, Ni and Mn lowered it.
(2) In the Fe-B ternary alloys solution-quenched, the aciccular structure consisting of body-centered cubic appeared, and the fomation of this structure was closely related to the cooling rate and the alloying element.
(3) Si, Ni, Mn and Cr had a weak tendency to form alloy boride (special boride) and mainly formed iron boride, but Ti, Zr, Nb, Mo and W had a strong tendency to form alloy boride.
(4) W, Nb, Mo, Ti and Zr forming the fine-distributed alloy boride markedly increased the hardness of the Fe-B alloy annealed and solution-quenched.
(5) In the tempering of Fe-B ternary alloys after water-quenched from 1100°C, a secondary hardening associated with the precipitation of iron boride or alloy boride was found. In the specimens alloyed with Ni, Si and Cr, the peak hardness was developed at 100° to 200°C, but at 450° to 600°C in cases of Nb, Mo and W.
(6) W, Nb, Mn and Mo markedly increased the tensile strength of Fe-B alloys air-cooled and water-quenched at room temperature, but deteriorated their ductility and toughness.
