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首页> 外文会议>6th Japan-France Materials Science Seminar JFMSS-6 on Microstructural Design for Improved Mechanical Behaviour of Advanced Materials Oct 4-6, 1999, Poitiers, France >Microstructural design criteria of fully lamellar TiAl alloys for improved creep strength
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Microstructural design criteria of fully lamellar TiAl alloys for improved creep strength

机译：改善蠕变强度的全片状TiAl合金的显微组织设计标准

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摘要

Grain size, volume fraction of constituent phases, lamellar spacing and lamellar orientation are the major microstructural variables to be considered in alloy design of fully lamellar TiAl alloys. Effects of the four variables on creep strength of TiAl alloys were studied by using polycrystalline specimens and PST (single grain) crystals. Creep rate of TiAl alloys is independent of grain size, and insensitive to the phase volume fraction (i.e. aluminum concentration). Grain size can be reduced down to 100 μm without loosing creep strength. Aluminum concentration is essentially free in the alloy design as far as creep strength is concerned. Creep rate of the alloys decreases with decreasing lamellar spacing, suggesting that refinement of lamellar micro structure is effective in improving creep strength. However, the strengthening by lamellar refinement disappears at low stress due to the increasing contribution of microstructural instability of fine lamellar microstructure. Stabilization of lamellar microstructures is necessary to prevent this loss of creep strength. Creep rate of the hard-orientated PST crystals, in which lamellar plates are aligned parallel or perpendicular to the stress axis, is reduced by two orders of magnitude with respect to the soft orientation. Creep strength of polycrystalline TiAl alloys can be improved significantly by the control of their texture.
机译：晶粒度，组成相的体积分数，层状间距和层状取向是全层状TiAl合金的合金设计中要考虑的主要微观结构变量。通过使用多晶试样和PST（单晶粒）晶体研究了这四个变量对TiAl合金蠕变强度的影响。 TiAl合金的蠕变速率与晶粒尺寸无关，并且对相体积分数（即铝浓度）不敏感。晶粒尺寸可减小至100μm，而不会降低蠕变强度。就蠕变强度而言，铝合金设计中的铝含量基本没有。合金的蠕变速率随着层状间距的减小而降低，表明层状微结构的细化可有效改善蠕变强度。然而，由于细小层状微结构的微结构不稳定性的增加贡献，层状细化的强化在低应力下消失了。为了防止这种蠕变强度的损失，必须稳定层状微结构。相对于软取向，其中薄板平行或垂直于应力轴排列的硬取向PST晶体的蠕变速率降低了两个数量级。通过控制其质地，可以显着提高多晶TiAl合金的蠕变强度。

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