Sc对Ti-Al二元合金组织与显微硬度的影响

Effect of Scandium on Microstructures and Microhardness of Ti-Al Binary Alloys

采用真空电弧熔炼技术制备了Ti 6Al、Ti 3Al 3Sc、Ti 10Al以及Ti 8Al 2Sc四种成分的合金 ,借助X射线衍射技术 (XRD)对铸态合金的相组成进行了分析。将铸态合金分别在β相区、α +β相区和α相区的温度下进行真空等温退火 10h并进行水冷。借助光学金相显微镜对合金在不同退火态下的组织进行了分析 ,并用岛津显微硬度计测量了合金的显微硬度。试验结果表明 ,铸态Ti Al (Sc)合金的显微组织形貌主要为魏氏组织、双态组织和网篮组织 ,其主要析出相为Ti3Al和Al3Sc。金属Sc的加入明显细化了合金的组织 ,同时提高了合金中α片层组织的显微硬度。从金属Sc对合金的组织演变的影响上来看 ,金属Sc的加入具有稳定α相的作用。经过等温退火处理后的合金其显微硬度高于铸态合金的显微硬度 。

The four alloys,including Ti-6Al,Ti-3Al-3Sc,Ti-10Al and Ti-8Al-2Sc,were prepared by vacuum arc melting method.Phase composition of the as-cast alloys was analyzed by X-ray diffraction.As-cast alloys were isothermally annealed for 10 hours under the temperature of β phase region、(α+β) phase region and α phase region,respectively,and then quenched by water.Microstructures of the as-cast alloys and the alloys annealled at different temperatures were analyzed by optical microscopy.Microhardness of the alloys was measured by SHIMADZU HMV microhardness tester.The results show that microstructures of these alloys as-cast were Widmansttten,bi-modal and basket-wave structures.The main precipitated phases of the alloys were Ti_3Al and Al_3Sc.The addition of metal scandium could refine the microstructures significantly,and improve the microhardness of α lamellars.From the influence of metal scandium on the microstructure evolution,it is observable that the addition of scandium played a role of stabilizing α phases.After isothermally annealing,the microhardness of the alloys were higher than that of as-cast alloys.The content of Al and the addition of Sc both influence microhardness of matrix and lamellars in some extent.