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P-B比（pilling-bedworth ratio）
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| 金属与氧结合在金属表面生成的氧化物膜中的每个金属离子体积与金属中的每个金属原子体积之比。反映氧化物膜中的应力状况。P-B比在l～2之间的金属，其表面氧化物膜中产生一定程度的压应力，膜比较致密，金属抗氧化性强。P-B比小于1或大于2时，氧化物膜中产生张应力或过大的压应力，容易造成膜破裂，金属抗氧化性低 |
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A correlation between the radius of curvature of metallic substrates with strainfree coherent monolayers of oxides and the Pilling-Bedworth ratio was found to follow the expression |R|≈19.5/|φ–1| for a large number of metal- oxide systems in which the metal and the oxide have identical cubic structures. For any given Pilling-Bedworth ratio φ, the radius of curvature of basally oriented hexagonal substrates was lower than that when the surface was perpendicular to the basal plane. Based on the theory of Pilling-Bedworth ratio (PBR) for metals, PBR for oxidation of alloys is suggested as. Three Al2O3 forming alloys (Ni3Al, NiAl and NiAl3) were used as examples to calculate PBR with this method. The results showed significant discrepancies compared with the PBR calculated with aluminium metal. Calculation with the traditional method gave the PBR value for oxidation of Al as 1.29; calculations with the modified method gave the PBR values for Ni3Al, NiAl and NiAl3 alloys as 1.71~1.88, 1.64~1.78, and 1.48~1.57, respectively. |
2楼2007-07-31 14:14:49
