【摘要】 利用四轴X射线衍射仪(XRD)测定片状DD10镍基单晶高温合金减薄至不同厚度时基体相(γ)和沉淀强化相(γ′)的晶格常数.根据减薄过程中两相间约束变化得到晶格常数和错配度变化规律,计算出合金从三维块体错配应力状态向二维平面应力状态转化达到失稳状态的临界厚度以及与不同应力状态对应的晶格错配度.依照一定的假设条件,推算出与应力松弛条件对应的无错配应力状态下两相的晶格常数.分析结果表明:合金减薄达到临界厚度后,γ′相晶格常数随厚度减小而线性变小,γ相晶格常数无明显变化,与此对应的晶格错配度绝对值变大;减薄过程伴随γ/γ′两相间约束的减弱和相间微观应力松弛,晶格取向差和晶体嵌镶度增大,表层应力状态向平面应力状态转化.测量得到的临界厚度与无错配应力状态下的晶格常数可为高温合金单晶材料的应用设计和残余应力测试提供参考.更多还原

【Abstract】 The lattice constants of the matrix phase 7 and the precipitated phaseγ’ in a waferlike nickel-base single crystal superalloy DD10 were determined by four-axis X-ray diffractometer (XRD).The variations of the lattice constants and lattice mismatches ofγandγ’ phases in the alloy wafer with different thicknesses,i.e.,different interphase restriction conditions were obtained.A critical thickness of the alloy wafer to reach an unstable stress state was defined based on the observed changes of lattice mismatch associated with a transformation of stress state from the 3D bulk state to 2D plane state.The lattice mismatches corresponding to different mismatch stress states were calculated. The lattice constants of theγandγ’ phases under a relaxed non-mismatch stress state were evaluated based on certain assumptions.The results showed that after the thickness of the alloy wafer reached the critical value,the lattice constant of theγ’ phase decreased linearly with the decrease of the thickness,whereas that of theγphase kept nearly constant,resulting in a linear increase of the absolute value of lattice mismatch.Accompanied with the thinning process,the crystal lattice misorientation and the mosaicity increased,theγ/γ’ interphase restraint reduced and the interphase stress relaxed, and the measured stress state changed to the plane state.The estimated critical thickness and the lattice constants under non-mismatch stress state could provide references for the design of the components and the measurement of the residual stress in the superalloy.更多还原