镍基单晶高温合金[111]取向拉压不对称分析

试验表明,[111]取向镍基单晶高温合金宏观滑移迹线符合六面体滑移特征,而微观位错滑移机制为八面体滑移。针对上述宏、微观现象,提出了一种"之"字形交滑移模型,使宏观六面体滑移迹线与微观位错的八面体滑移在该模型中得到了很好的统一。同时,在上述"之"字形交滑移变形机制的基础上,对[111]取向的拉压不对称特性进行了分析,提出一种位错分解方式,对[111]取向产生拉压不对称特性的微观机制进行了表征。最终,基于上述两种机理,建立了[111]取向镍基单晶高温合金的拉压不对称预测模型。该模型不仅能够对[111]取向镍基单晶高温合金屈服强度进行预测,而且可以表征屈服强度的拉压不对称特性,即压缩屈服强度大于拉伸屈服强度以及拉压不对称随温度升高愈加严重的现象。

The Study of Tension/Compression Asymmetry of [111] Oriented Nickel Base Single Crystal Superalloys

The results of experiments show that the macroscopic deformation bands of [111] oriented nickel base single crystal superalloys belong to cubic slip mechanism and microscopic dislocations slip is octahedral. For above results, a zig-zagged cross slip model has been proposed to interpret above phenomenon. This model could characterize both macroscopic cubic deformation and microscopic octahedral slip well. The gradual decrease of the yield strength of nickel base single crystal superalloys with increasing of temperature has been also studied and the model could interpret this phenomenon well. Based on above zig-zagged cross slip model, the tension/compression asymmetry of [111] oriented nickel base single crystal superalloys has been studied and a dissociation mechanism of the superdislocation which could predict the yield strength of tension lower than that of compression has been also proposed. Finally, based on above cross slip model and dissociation mechanism, a yield strength predicted model has been proposed which could characterize tension/compression asymmetry of [111] oriented nickel base single crystal superalloys.