共查询到16条相似文献,搜索用时 46 毫秒
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对单晶高温合金DD6进行表面渗碳处理,采用SEM、TEM研究了DD6合金渗碳层组织,运用EDS与SAD分析了渗碳层内碳化物的类型。结果表明,表面渗碳处理后,在渗碳层γ相内析出大量细小的MC型碳化物,与合金名义成分相比,其化学成分富含铌、钽和钼,而铝和镍含量较低。该碳化物呈块状析出,尺寸约为0.1μm,弥散分布在渗碳层区域内。由于碳化物的析出,渗碳层区域内的γ′相不能保持完整的立方化形态。渗碳处理温度越高,渗碳层深度越大。MC碳化物与基体γ相之间存在[001]MC∥[001]γ,(200)MC∥(200)γ的晶体学取向关系。 相似文献
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为优化一种单晶高温合金中的Re含量,在真空定向凝固炉中制备了3%Re和5%Re的镍基单晶高温合金,热处理后分别在980 ℃长期时效400、800、2 000 h,测试合金热处理后1 100 ℃拉伸性能,采用JMatPro软件计算了合金相图,通过光学显微镜、扫描电镜和能谱仪研究Re含量对合金枝晶组织,热处理组织和980 ℃时效400、800、2 000 h的组织和1 100 ℃拉伸性能的影响。结果表明,随着单晶高温合金中Re含量增加,一次枝晶间距轻微减小,共晶的体积分数升高;γ′相尺寸下降,立方化程度增加;不同Re含量合金时效800 h后无TCP相析出,时效2 000 h后有TCP相析出,随着Re含量增加,TCP相析出量增加。合金组织稳定性随着Re含量增加而降低。随着Re含量增加,合金的高温拉伸性能显著提高。 相似文献
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DD6单晶镍基高温合金中含有Ta、Re、W等合金元素,因此样品溶解较为困难,得到的样品溶液也不稳定。实验采用盐酸-硝酸体系溶解样品,以镍基体匹配法绘制校准曲线克服了基体镍的干扰,实现了氢化物发生-原子荧光光谱法对DD6单晶镍基高温合金样品中As含量的测定。对溶样方法进行了探讨,结果表明,采用20mL盐酸-5mL硝酸、加热(100℃左右)溶解样品后,虽然会有少量不溶物存在,但待测元素As已完全溶出,即不溶物中未夹带元素As,因此实验选择该溶样方法进行溶样。对仪器的负高压、灯电流进行了优化试验,确定负高压为280V,灯电流为60mA。根据样品中镍的含量,分别采用无基体匹配和镍基体匹配法建立校准曲线,结果表明,对于同样质量浓度的As标准溶液,有基体镍存在时的测定结果均较无基体镍时明显偏低,说明镍基体的干扰对测定不可忽略,故实验采用镍基体匹配法绘制校准曲线。方法线性范围为0.00005%~0.001%,方法检出限为2×10-5μg/mL。按实验方法对6个DD6单晶镍基高温合金样品进行测定,测得结果与高流速辉光放电质谱法基本一致,测得结果的相对标准偏差(RSD,n=8)为2.3%~8.7%。 相似文献
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在定向凝固炉中采用螺旋选晶法制备了一种单晶高温合金试棒,标准热处理后分别在980 ℃,1 070 ℃,1 100 ℃和1 140 ℃长期时效处理500 h,研究了不同温度长期时效后合金的显微组织和1 100 ℃的拉伸性能.结果表明合金在不同温度长期时效后,γ′相发生粗化或筏排化.随着时效温度增加,γ′相粗化或筏排化程度增加,γ′相体积分数减少,γ相基体通道变宽.在980 ℃长期时效500 h后,无TCP相析出;1 070 ℃,1 100 ℃,1 140 ℃长期时效500 h后,有针状TCP相析出.随着长期时效温度增加,TCP相含量增加.随着时效温度升高,合金拉伸强度降低,拉伸延伸率先增加后在1 140 ℃时效时又降低.长期时效后γ′相粗化或筏排化、γ′相含量减少和TCP相析出是合金拉伸强度降低的主要原因. 相似文献
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《钢铁研究学报(英文版)》2015,(8)
Tensile properties of the second generation single crystal superalloy DD6 were investigated from 20 °C to 1 100 °C. Microstructure evolution and fracture mechanism were examined by scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The results show that the tensile strength decreases slightly with increasing temperature from 20 °C to 400 °C. The tensile strength of the alloy increases with the increase of temperature from 400 °C to 800 °C. Above 800 °C, the yield strength of the alloy decreases greatly with increasing temperature. The elongation and contraction of area almost present opposite tendency in contrast to changes of the tensile strength. At lower and intermediate temperature(from 20 °C to 850 °C), the tensile fracture mechanism shows quasi-cleavage mode, while at high temperature(980 °C and 1 100 °C), it is dimple mode. The γ′ precipitate morphology still maintains cubic after tensile fracture at lower and intermediate temperature. The γ′ phase changes into rectangular solid at high temperature. The γ′ phase is sheared by anti-phase boundary(APB) or stacking faults at lower and intermediate temperature. At high temperature, dislocations overcome γ′ through by-passing mechanism. 相似文献
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DD6 single crystal superalloy slabs were prepared with seed method in the directionally solidified furnace with high temperature gradient. The transverse stress rupture properties and fracture behaviour of the alloy at 760 ℃/758 MPa, 850 ℃/550 MPa and 980 ℃/250 MPa were investigated and compared with those of longitudinal specimens. The transverse stress rupture lives are corresponding with the longitudinal stress rupture lives at 760 ℃/758 MPa and 850 ℃/550 MPa. The transverse stress rupture lives are slightly less than the longitudinal stress rupture lives at 980 ℃/250 MPa. The fracture mechanism of the transverse stress rupture of the alloy at 760 ℃/758 MPa shows quasi-cleavage mode and the fracture mechanism at 980 ℃/250 MPa shows dimple mode, while the fracture mechanism at 850 ℃/550 MPa shows quasi-cleavage and dimple mixture mode. At higher temperature and lower stress, the microcracks are easier to initiate and interconnect in the transverse specimen than those in longitudinal specimen because there are interdendritic regions perpendicular to the axis of stress. 相似文献
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The specimens of the second generation single crystal superalloy DD6 with different Hf contents were prepared in the directionally solidified furnace with a high temperature gradient. The long term aging of the specimens after full heat treatment was performed at 1040 ℃ for 800 h. The effect of Hf on the microstructure and stress rupture properties under 980 ℃/250 MPa of the alloy after long term aging was investigated. The results show that the γ′ coarsening and rafting and no topologically close packed phase (TCP) are observed in the microstructures of DD6 alloy with different Hf contents after aged at 1040 ℃ for 800 h. It indicates that DD6 alloy with different Hf contents all possesses good microstructure stability. With increasing Hf content the rupture life after long term aging turns shorter and the elongation represents the increasing first and decreasing afterwards. The fracture mechanism of the alloy with different Hf contents at 980 ℃/250 MPa all shows dimple model. The influence of the microstructures on the stress rupture properties of the alloy is also discussed. 相似文献
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一种镍基单晶高温合金的显微偏析行为 总被引:5,自引:0,他引:5
研究了一种新型镍基单晶高温合金DD98铸态组织的显微偏析行为.实验结果表明,当合金以枝晶凝固时,组织中存在显微偏析.其中元素Mo、Cr、Ti、Ta、Al在枝晶间富集,Ti、Mo、Ta、Cr的偏析较为严重,Al的偏析程度相对小一些,Ni、Co、W为枝晶干偏析元素,其中W的偏析最为严重;共晶中富集Al、Ta、Ti、Ni,贫Co、W、Cr、Mo.凝固速率对枝晶偏析有显著的影响.随着抽拉速率的增加,元素Al、Mo、Co、Ti的偏析程度增加,而Ta的偏析程度降低,其它元素的偏析程度变化不大. 相似文献
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研究了直流电场对DD3单晶高温合金凝固显微偏析的影响.实验结果表明在定向凝固速度为5μm/s和电流密度为0~20 A/cm2的条件下,随电流密度增大,胞晶或树枝晶间距减小.与不施加电场时相比,电流密度为6A/cm2时,凝固偏析明显减轻;电流密度为20A/cm2时,凝固偏析恶化.DD3单晶高温合金定向凝固过程中,由于电场的加入,引起溶质有效再分配系数的变化,减轻了凝固偏析;胞晶或树枝晶间距减小,也有利于减轻凝固偏析;胞晶间的原子团簇向胞晶侧面集聚,造成凝固偏析增大.上述因素共同作用决定了最终凝固组织的偏析. 相似文献