氢化钛-石墨制备Al-Ti-C母合金的机理与组织

Mechanism and Microstructure of Al-Ti-C Mother Alloy Prepared by Titanium Hydride-graphite

采用扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射(XRD)等研究了由氢化钛-石墨法制备的Al-Ti-C母合金的组织性能。结果表明:由氢化钛-石墨与铝液反应制备Al-Ti-C母合金的机理是由氢化钛、石墨分别作为钛源、碳源,氢化钛受热分解为钛和氢,钛与铝、石墨反应生成钛铝、钛碳或者铝碳化合物。由铝钛化合物、碳铝化合物、钛碳化合物组成具有细化作用的Al-Ti-C母合金。合金的物相组成包括:α(Al)、铝钛、碳铝、钛碳化合物等物相,金相组织为等轴晶或者树枝晶,平均晶粒尺寸20～40μm。合金基体中存在针片状、长条状的初晶相,晶界上存在含钛、碳、铁、硅的花瓣状初晶,钛、碳组元沿晶界、晶内分布大体均匀,在初晶相附近存在明显的钛、碳富集、偏聚现象。冰晶石有利于碳与铝润湿、反应,生成的第二相在晶内扩散更充分、分布也更均匀。

The microstructure and properties of Al-Ti-C master alloy prepared by titanium hydride and graphite were studied by X-ray diffraction(XRD), scanning electron microscope(SEM) and energy dispersive spectrometer(EDS). The results show that the mechanism of Al-Ti-C alloy prepared by the reaction of titanium hydride-graphite and aluminum liquid is that titanium hydride and graphite are respectively used as titanium and carbon sources, and titanium and hydrogen are obtained by thermal decomposition of titanium hydride.Titanium react with aluminum and graphite to form titanium-aluminum, titanium-carbon or carbon-aluminum compounds. Titanium aluminum, carbon aluminum and titanium carbon compounds form refined Al-Ti-C alloy. The phase composition of the alloy includesα(Al), Ti-Al, C-Al, Ti-C compounds and other phases. The microscopic structure is equiaxed or dendrite structure, and the average grain size is 20~40 μm. There are needle like or rod like primary crystals in the alloy matrix. There are petal like primary crystals containing titanium, carbon, iron and silicon on the grain boundaries. The titanium and carbon elements distribute evenly along the grain boundaries and the grains. There is obvious titanium and carbon enrichment and segregation near the primary phase. Cryolite is conducive to the wetting and reaction of carbon and aluminum, and the second phases generated diffuse more fully and uniformly in the grain.