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    热压烧结Nb-23Ti-15Al超高温合金的压缩性能及其变形机制

    Compressive Properties and Deformation Mechanisms of Hot-Pressed Sintered Nb-23Ti-15Al Ultra-High Temperature Alloys

    • 摘要: 采用热压烧结工艺在不同温度(1 350,1 440 ℃)下制备Nb-23Ti-15Al合金,研究了合金的室温和高温(1 100 ℃)压缩变形行为及其变形机制。结果表明:1 350,1 440 ℃烧结所得合金的室温抗压强度分别高达1 740,2 200 MPa,但合金均未发生屈服即断裂,室温脆性较大。高温压缩时两种温度烧结所得合金的抗压强度相近并表现出良好塑性,应变超过50%而不断裂,且出现应变软化现象;1 440 ℃烧结所得合金的应变软化更显著。高温压缩时,两种温度烧结所得合金的变形均集中于β相。1350 ℃烧结所得合金中β相存在位错缠结及位错弯折,未见明显滑移带,变形局域化程度较轻,δ相中仅存在少量平行位错,部分Ti(O,C)相中存在弯曲位错或位错列;1 440 ℃烧结所得合金β相变形局域化显著,β相中出现明显滑移带,带内塞积大量位错。

       

      Abstract: Nb-23Ti-15Al alloys were synthesized via hot-pressing sintering at different temperatures (1 350 ℃, 1440 ℃), and their compressive deformation behaviors and deformation mechanisms of the alloys at both room temperature and high temperature (1 100 ℃) were investigated. The results show that the room-temperature compressive strengths of the alloys sintered at 1 350 ℃ and 1 440 ℃ reached 1 740 MPa and 2 200 MPa, respectively.. However, both alloys fractured without yielding during room temperature compression, indicating the high brittleness at room temperature. Under high temperature compression, the compressive strengths of the alloys prepared at the two sintering temperatures were similar, and both exhibited excellent plasticity, with strains exceeding 50% without fracture, along with noticeable strain softening. The strain softening was more pronounced in the alloy sintered at 1 440 ℃. During high temperature compression, deformation in both alloys was concentrated in the β phase. In the alloy sintered at 1 350 ℃, dislocation tangles and kinks were observed in the β phase, with no obvious slip bands, indicating relatively low deformation localization. Additionally, only a few parallel dislocations were present in the δ phase, and curved dislocations or dislocation arrays were identified within some Ti(O, C) phases. In contrast, the alloy sintered at 1 440 ℃ showed significant deformation localization in the β phase, where distinct slip bands were formed, and a high density of dislocations was accumulated within these bands.

       

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