Internal oxidation method of metals and alloys with internally dispersed oxygen sources

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Hard and brittle oxide particles can be dispersed finely and uniformly in the matrices of ductile metals by mechanical alloying (MA). In case that the dispersed oxide is thermodynamically unstable with respect to the matrix metal, the oxide particles act as the oxygen sources, and more stable oxide is formed by the displacement reaction of oxygen. In this work, Cu alloys and magnesium were mechanically alloyed with addition of various metal oxides, and in situ formation of oxide dispersoids was studied in the matrix of Cu and Mg. It is a purpose of this work to obtain high performance materials by effective dispersion strengthening attained by such a process.All the obtained MA powders showed the structures in which fine oxide particles were uniformly dispersed in the matrix of Cu or Mg. In mechanically alloyed Cu alloys containing solute elements whose oxidation tendency is stronger than Cu, the added oxide particles acted as the supply source of oxygen and internal oxidation of solut … More e atoms occurred. In MA of Cu-Zn, Cu-Sn, Cu-Ni and Cu-Al alloys with addition of CuO, the displacement reaction of oxygen took place, thereby ZuO, SnOィイD22ィエD2, NiO, and AlィイD22ィエD2OィイD23ィエD2 were formed by preferential oxidation of the solute elements. Furthermore, when MA was performed for the Cu-Al alloy with additions of ZnO, NiO, and CrィイD22ィエD2OィイD23ィエD2, preferential oxidation of solute Al caused in situ formation of AlィイD22ィエD2OィイD23ィエD2 in the matrices of Cu-Zn, Cu-Ni and Cu-Cr alloys. It has been shown that the P/M materials of high strength can be obtained by applying such internal oxidation processes.In MA of pure Mg with addition of SiOィイD22ィエD2, displacement reaction of oxygen occurred and the in situ formation of MgO and MgィイD22ィエD2Si was confirmed by X ray diffraction. The reaction progressed further by heating the MA powder, and hardness increased were observed along with it. In MA of pure Mg with addition of TiOィイD22ィエD2, complex oxide MgTiOィイD23ィエD2 was formed by heating of the MA powders. However, decomposition of ZrOィイD22ィエD2 was not observed after heating of the MA powders of Mg-ZrOィイD22ィエD2. In the bulk material of Mg-SiOィイD22ィエD2 prepared by vacuum hot press, the hardness reached HV162 due to internal oxidation. Less