単ロール式急冷凝固法で作製したMg-Sc 合金のヌープ硬さに及ぼす Zr 添加の影響 ^†

Recently, it has been found that Mg-Sc alloys with a body-centered cubic (bcc) structure have excellent workability, strength and ductility, and exhibit superelasticity at room temperature. However, due to the high cost of Sc, such alloys have not yet been put into practical use. Therefore, in this study, Zr, which is less expensive than Sc, was added to a Mg-Sc alloy, and a single-roll rapid solidification method was used to directly obtain ribbons from the molten metal. The thickness of the resulting alloy ribbons was measured using a digital microscope, the crystal phase was identified using X-ray diffraction (XRD) analysis, the microstructure was observed using field-emission scanning electron microscopy, and the hardness was evaluated by a Knoop hardness test. The results indicated that continuous Mg-Sc-Zr alloy ribbons with a uniform width and a thickness of about 50 μm could be obtained. From the XRD results, the rapid cooling process caused an increase in the fraction of the bcc phase relative to that in a Mg-Sc ingot; this phase is stable at higher temperatures. The Knoop hardness of the Mg-Sc-Zr alloy ribbons was found to increase with increasing Zr content, which is considered to be due to microstructural refinement.