【作者】 刘臣；

【导师】 田素贵； 尚丽娟；

【作者基本信息】 沈阳工业大学 ， 材料学， 2012， 硕士

【摘要】 本文通过对等温锻造GH4169G合金进行不同条件的热处理、蠕变性能测试及组织形貌观察,研究了热处理制度对合金蠕变性能的影响;通过蠕变曲线的测定及变形合金的微观形貌观察,计算出不同工艺处理合金的蠕变激活能和应力指数,研究了不同状态合金在蠕变期间的变形与断裂机制。结果表明:ITF-GH4169G合金的晶粒尺寸约为15~20μm,其组织结构由γ基体、γ′、γ″、δ相及碳化物组成,经不同工艺热处理后,析出相具有不同的形态。经直接时效处理合金中沿晶界析出粒状δ相,经标准热处理,合金中沿晶界可析出大量针状和块状δ相,其中,δ相中富含Cr、Fe是使其具有针状形态的主要原因。与其它处理工艺相比较,经直接时效处理合金具有较好的蠕变抗力,测定出DA-GH4169G合金在660°C/650MPa条件下的蠕变寿命为295小时,在试验的温度和应力范围内,计算出该合金的蠕变激活能为:532.7kJ/mol。蠕变期间合金的变形机制是位错滑移和孪晶变形,测定出合金的孪晶面为{111},其中,微量P、B可促使沿晶界析出粒状碳化物相,并抑制晶界滑移,是使合金具有较好蠕变抗力的主要原因。在蠕变的后期,首先在样品表面出现单取向特征的滑移迹线,随蠕变进行,当激活另一滑移迹线或孪晶切过滑移迹线时,可改变原滑移迹线方向,或在原滑移迹线处形成滑移台阶。蠕变期间合金易于沿垂直于应力轴的晶界发生裂纹萌生,随蠕变进行,裂纹可沿垂直于应力轴的晶界扩展,或与应力轴方向成一定角度扩展,直至发生合金蠕变的沿晶断裂。与无P、B合金相比,GH4169G合金蠕变断裂的断口呈现非光滑表面,其中,添加微量P、B可提高合金晶界的结合强度,抑制晶界滑移,是改善合金蠕变抗力、致使蠕变断口呈现非光滑表面的主要原因。更多还原

【Abstract】 In the paper, by means of heat treatment at different conditions, creep properties measurement and microstructure observation, the influence of heat treatment regimes on the creep properties of the GH4169G alloy is investigated. In the further, the creep activation energy and stress exponent of the alloy are calculated according to the data of the creep curves, and the deformation and fracture mechanisms of the alloy during creep are discussed.Results show that, the grain size of ITF-GH4169G alloy is about 15~20μm, and the microstructure of the alloy consists of theγ,γ′,γ″,δphases and carbides. The precipitated phase in the alloy treated by different regimes displays the various configuration. The particle-likeδphase is precipitated along the boundaries after direct aged (DA), and the needle-likeδphase is precipitated along the boundaries after standard heat treatment (STD). Thereinto, the elements Cr and Fe is thought to be the main reason of theδphase transformed into the needle-like configuration. Compared to other treatment technologies, GH4169G alloy treated by direct aged displays the better creep resistance. And the creep lifetime of the alloy at 660℃\650MPa is measured to be 295, in the ranges of the applied temperatures and stresses, the activation energy of DA-GH4169G alloy during steady state creep is calculated to be 532.7kJ/mol. The deformation mechanisms of GH4169G alloy during creep is the dislocations slipping and twinning, and the twinning plane activated in the alloy during creep is determined as {111} plane. And it is thought that the traces phosphorus and boron may promote the particle-like carbides precipitated along the boundaries to restrain the boundaries slipping, which is thought to be the main reason of alloy displaying the better creep resistance.During creep of the alloy, the slipping traces with single oriented feature appear in the surface of the sample. As the creep goes on, the direction of the slipping traces is changed or the slipping step is kept in the original trace when the activated another slipping trace or twinning shears through the trace. During the later stage of creep, the cracks are easily initiated along the boundaries vertical to the stress axis, as the creep goes on, the cracks are propagated along the boundaries up to occurring creep fracture. Compared to GH4169 alloy, the creep fracture of GH4169G alloy displays the non-smooth surface, thereinto, the adding trace phosphorus and boron may improve the adhesive strength of the boundaries and restrain the boundaries slipping to enhance the creep resistance of the alloy, which is the main reason of the creep fracture displaying the non-smooth surface.更多还原