研究结果表明,难变形镍铬钴基高温合金,在长期时效中,微量和少量σ相的析出,对合金的力学性能没有明显的影响;析出多量σ相,则显著降低合金的室温拉伸、冲击韧性、持久、蠕变和断裂韧性,此时材料的断裂沿σ相界面发展。但对高温拉伸性能没有影响。 σ相在室温是一种硬而脆的相,在较高温度时显示了一定塑性,可以发生较大变形。
An investigation has been carried out on the effect of σ-phase on the mechanical properties of a Ni-Cr-Co based superalloy. Specimens treated to different amount of σ-phase were compared with the same alloy without such phase. It was found that specimens containing σ-phase up to 0.7% (by volume)showed little deterioration in properties, whereas in the case of those with σ-phase amounted to 2—4%, the room temperature tensile strength, impact toughness, endurance, creep and fracture toughness of the alloy were very markedly lowered. Moreover, cracks along the interfaces between the σ-phase grains and the matrix were often observed. Tensile properties at high temperatures, however, seems to be little affected by such phase. It would appear that σ-phase, being hard and brittle at room temperature, becomes deformable at elevated temperatures.
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