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本文研究了通过特殊热处理的方法获得弯曲晶界(锯齿晶界),以改善高温合金 GH220的高温强度及塑性。研究指出,单纯获取弯曲晶界并不能达到改善高温强度的目的,合理的热处理工艺,应该既能获得弯曲晶界并能使晶内的γ′相大小、形态、分布合理,才能使晶界和晶内强度得以配合。本文研究的1220℃×4h 空冷至1070℃×2.5h 空冷,及950℃×2h 空冷,的热处理工艺达到了上述要求,使 GH220合金的高温强度,特别是塑性指标获得明显的改善。在获得弯曲晶界的热处理过程中,M_6C 型碳化物是引起晶界局部迁移并形成弯曲晶界的主要因素。这与以往的某些 Ni 基合金的研究结果显著不同。同时从机理上讨论了碳化物引起弯曲晶界形成的条件以及弯曲晶界对改善高温强度及塑性指标的作用。
In this paper, the bending grain boundaries (sawtooth grain boundaries) were obtained by special heat treatment to improve the high temperature strength and ductility of superalloy GH220. It is pointed out that simply obtaining the curved grain boundaries can not achieve the purpose of improving the high temperature strength. Reasonable heat treatment process should not only achieve the bending grain boundaries but also make the γ ’phase size, shape and distribution in the crystal reasonable so that the grain boundaries and Crystal strength to be matched. In this paper, 1220 ℃ × 4h air-cooled to 1070 ℃ × 2.5h air-cooled, and 950 ℃ × 2h air-cooled, heat treatment process to achieve the above requirements, GH220 alloy high temperature strength, especially the plastic index was significantly improved. In the process of heat treatment for obtaining the curved grain boundary, the M_6C carbide is the main factor causing the grain boundary to migrate locally and form the bent grain boundary. This is significantly different from the previous studies on some Ni-based alloys. At the same time, the mechanism of the formation of bending grain boundary caused by carbides and the effect of bending grain boundaries on the improvement of high temperature strength and plasticity are discussed from the mechanism.