元素V对DZ417G高温合金组织和性能的影响

发布时间：2018-06-08 04:22

本文选题：DZ417高温合金 + V元素　；参考：《沈阳工业大学》2017年硕士论文

【摘要】：通过真空定向凝固技术制备出具有V含量分别为0.69%、0.96%和1.04%的DZ417G柱状晶高温合金,并对其进行组织观察、相组成分析、蠕变性能测试、拉伸性能测试及长时效处理,深入探讨了V对DZ417G合金组织及性能的影响。扫描电子显微镜观察不同V含量铸态和热处理态合金γ'相及碳化物形貌表明:随合金中V含量增加,合金中碳化物形貌逐渐由棒状转变为块状,对棒状和块状碳化物进行能谱分析表明,棒状碳化物中Cr、Al、Co等非MC型碳化物形成元素较多,而块状碳化物中Ti、Mo、V等MC型碳化物形成元素较多。随V含量增多,合金中γ'相形貌几乎不变,但能谱分析表明:γ'相中V含量亦随合金中V含量增加而增加。采用电解法萃取合金中的γ'相,并对不同V含量热处理态及铸态合金中的γ'相进行XRD衍射分析,结果表明:合金中γ基体相主要为Ni,Cr,Co,Mo,Ti,Al元素组成的固溶体,γ'相主要为Ni3[Al,Ti],碳化物主要是MC型的VC和[Ti,Mo]C。测定出合金中γ相及γ'相的晶格常数,并计算晶格错配程度,随合金中V含量增加,合金中γ相及γ'相的晶格常数均减小,γ/γ'两相晶格错配度降低。热处理后对不同V含量合金进行中温及高温蠕变性能测试表明,随V含量增加,合金蠕变寿命均大幅增加,蠕变激活能及应力指数增加;观察裂纹的萌生及扩展表明,中温及高温蠕变期间,碳化物都是裂纹的主要发源地。对合金的微观组织观察表明,低V合金中位错迹线较长,位错主要以攀移绕过机制通过γ'相,而高V合金中位错迹线长度大幅度缩短,位错切入γ'相形成不全位错+层错组态。对热处理后不同V含量合金进行室温、中温及高温拉伸性能测试表明,室温条件下高V合金拉伸性能较好,中温条件下低V拉伸性能较好,高温条件下高V合金拉伸性能较好。断口观察表明,室温拉伸低V合金断口处分布大量细小碳化物,而高V合金断口处碳化物尺寸较大,数量较少;中温条件下,低V合金中滑移迹线较少,而高V合金中滑移迹线较多;高温拉伸条件下,低V合金断口平滑,高V合金韧窝较多,并存在大量滑移迹线。合金长时效处理1000h后,观察合金中的碳化物演化,表明:碳化物已经发生分解,棒状碳化物已经分解断开,而块状碳化物由边缘开始分解;时效期间γ'相形貌变化特征表明,随合金中V含量增多,γ'相长大速率加快;时效后含V0.69%合金较时效前合金的蠕变寿命增加,而含V0.96%及1.04%合金蠕变寿命降低。
[Abstract]:DZ417G columnar superalloys with V content of 0.69% and 1.04% were prepared by vacuum directional solidification technique. The microstructure, phase composition, creep properties, tensile properties and long aging treatment of DZ417G superalloys were investigated. The effect of V on the microstructure and properties of DZ 417G alloy was discussed. The morphology of 纬 'phase and carbides of as-cast and heat-treated alloys with different V contents were observed by scanning electron microscope (SEM). The results showed that the morphology of carbides in the alloys changed from rod-like to block-like with the increase of V content in the alloys. The energy spectrum analysis of rod and block carbides shows that there are more forming elements of non-MC type carbides such as Cr-AlC- Co in rod-like carbides, while there are more MC-type carbides in bulk carbides such as Tianmo-V. The morphology of 纬 'phase in the alloy was almost unchanged with the increase of V content, but the energy spectrum analysis showed that the V content in 纬' phase also increased with the increase of V content in the alloy. The 纬 'phase in the alloy was extracted by electrolysis, and the 纬' phase in the as-cast alloy and the heat treated state with different V content were analyzed by XRD diffraction. The results show that the 纬 -matrix phase is mainly a solid solution composed of NiCrCrCoCoMoTiTiAl, the 纬 'phase is mainly Ni3 [Alanti], and the carbides are mainly MC type VC and [TiTiMo] C. The lattice constants of 纬 phase and 纬 'phase in the alloy were measured and the lattice mismatch degree was calculated. With the increase of V content in the alloy, the lattice constants of 纬 phase and 纬' phase decreased and the mismatch of 纬 / 纬 'phase lattice decreased. After heat treatment, the creep properties of the alloys with different V contents were tested at moderate and high temperatures. The creep life and creep activation energy and stress exponent of the alloys increased with the increase of V content, and the crack initiation and propagation were observed. The carbides are the main source of cracks during the creep at moderate temperature and high temperature. The microstructure of the alloy shows that the dislocation trace line is longer in the low V alloy, the dislocation mainly passes through 纬 'phase by climbing around mechanism, while in the high V alloy, the length of the dislocation trace line is shortened greatly, and the dislocation cuts into 纬' phase to form the incomplete dislocation layer fault configuration. The tensile properties of the alloys with different V content after heat treatment were tested at room temperature, moderate temperature and high temperature. The results showed that the tensile properties of high V alloys were better at room temperature, low V tensile properties at medium temperature and good tensile properties at high temperature. Fracture observation shows that a large number of fine carbides are distributed at the fracture surface of low V alloy at room temperature, while the size of carbide at fracture surface of high V alloy is large and the quantity is small, and the slip trace line is less in low V alloy at moderate temperature. Under high temperature tensile condition, the fracture surface of low V alloy is smooth, the dimples of high V alloy are more, and there are a lot of slip trace lines in high V alloy. After long aging treatment for 1000h, the carbide evolution in the alloy was observed. The results show that the carbide has been decomposed, the rod carbide has been decomposed and the block carbide has been decomposed from the edge, and the morphology of 纬 'phase has changed during aging. With the increase of V content in the alloy, the growth rate of 纬 'phase increases, and the creep life of the alloy containing V0.69% increases, while the creep life of the alloy containing V0.96% and 1.04% decreases after aging.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG132.3

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