WC和SiC对TiAl二元合金组织和力学性能的影响

发布时间：2018-06-28 06:41

  本文选题：TiAl合金 + WC　； 参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：TiAl合金具有很多优异的综合性能,在航空航天有着广泛的应用。随着航空航天发动机向着更快更强的目标发展,TiAl合金作为结构材料的力学性能还需进一步提高。改善和提高TiAl合金性能的有效方法是合金化,或者是通过原位自生的方法生成增强相来提高合金的综合力学性能。本文采用真空电弧熔炼的方法在TiAl二元合金中加入WC和SiC,研究添加不同质量分数的WC和SiC对Ti43Al和Ti47Al二元合金的影响,通过OM、SEM、EPMA、XRD等方法观察和测试显微组织结构,并对其室温压缩性能进行了测试,研究在不同WC和SiC添加量下合金力学性能的变化规律,分析讨论WC和SiC对TiAl二元合金的作用机理和强化机制。实验结果表明,在Ti43Al中加入WC后,Ti43Al合金的显微组织得到细化,室温压缩强度和压缩率都得到一定的提升。当WC添加量为4.5wt%时,合金显微组织一次枝晶臂间距达到最小为70.65μm,压缩强度为1235.11MPa,与Ti43Al基体合金相比提高了46.62%。当WC添加量达到6.0wt%和7.5wt%时,基体片层组织中出现细长针状增强相,XRD分析表明增强相是Ti2AlC,且其室温压缩性能和压缩率逐渐下降。WC对Ti47Al的组织和性能也有一定影响,随着WC加入量的不断增加,基体片层中出现棒状增强相,且其数量逐渐增多,分布均匀,XRD分析表明基体中生成了Ti2AlC增强相,α2相的最强衍射峰向左偏移,Ti47Al-xWC合金的显微组织明显细化,由最初的柱状枝晶转变成四重对称等轴晶组织,晶粒尺寸由原始的141.86μm减小到60.02μm,室温压缩强度和压缩率都逐渐提升。当WC添加量为6.0wt%时,晶粒尺寸达到最小为60.02μm,室温压缩强度达到最大为2323.99MPa,与Ti47Al基体合金相比提高了21.19%。在Ti43Al中加入SiC后,当SiC添加量为0.1、0.3、0.5、0.7wt%时,Ti43Al-xSiC的组织和室温压缩性能变化不明显,但是当SiC的加入量达到0.9wt%时,晶粒尺寸为105.99μm,Ti43Al合金的显微组织由粗大的柱状晶组织变成细小的等轴晶组织。室温压缩强度大幅度提升,压缩强度达到1382.72MPa,与Ti43Al基体合金相比提高了64.14%。SiC对Ti47Al合金的组织和性能有显著的影响,当在Ti47Al中加入SiC后,随着SiC加入量的增多,基体片层中生成了细小棒状的Ti2AlC增强相,晶界处弥散分布大量的富Si析出相。当SiC添加量为0.5wt%时,压缩强度达到最大值为2196.49MPa,与基体合金相比提高了19.94%。
[Abstract]:Tial alloys have many excellent comprehensive properties and are widely used in aeronautics and astronautics. The mechanical properties of tial alloys as structural materials need to be further improved with the development of aerospace engines towards faster and stronger targets. The effective way to improve and improve the properties of tial alloys is to improve the comprehensive mechanical properties of tial alloys by alloying or by in-situ generation of reinforcing phases. In this paper, WC and sic were added to tial binary alloy by vacuum arc melting. The effect of WC and sic on Ti43Al and Ti47Al binary alloy was studied. The microstructure was observed and tested by OMSEMEPMA-XRD. The compressive properties at room temperature were tested and the mechanical properties of the alloys with different WC and sic contents were studied. The mechanism and strengthening mechanism of WC and sic on tial binary alloys were analyzed and discussed. The experimental results show that the microstructure of Ti43Al alloy is refined and the compression strength and compression ratio of Ti43Al alloy are improved at room temperature after adding WC into Ti43Al alloy. When the WC content is 4.5 wt%, the primary dendritic arm spacing of the alloy microstructure reaches the minimum of 70.65 渭 m and the compression strength is 1235.11 MPA, which is 46.62% higher than that of Ti43Al matrix alloy. When WC content reached 6.0 wt% and 7.5 wt%, XRD analysis showed that the reinforcing phase was Ti _ 2AlC, and the compression properties and compressibility of Ti _ (47) Al decreased gradually at room temperature. The microstructure and properties of Ti _ (47) Al were also affected by WC. With the increasing of WC content, the rod-like reinforcement phase appears in the matrix layer, and its number increases gradually. XRD analysis showed that Ti _ 2AlC reinforcement phase was formed in the matrix, and the microstructure of Ti _ 47 Al-xWC alloy with the strongest diffraction peak shifted to the left of 伪 _ 2 phase was obviously refined, which changed from columnar dendrite to four-fold symmetrical equiaxed structure, and the microstructure of Ti _ (47) Al-xWC alloy was changed from columnar dendrite to tetra-symmetric equiaxed structure. The grain size was reduced from 141.86 渭 m to 60.02 渭 m, and the compression strength and compression ratio increased gradually at room temperature. When WC content is 6.0 wt%, the grain size reaches the minimum of 60.02 渭 m and the maximum compression strength at room temperature is 2323.99 MPA, which is 21.19% higher than that of Ti47Al matrix alloy. When sic was added into Ti43Al, the microstructure and room temperature compressive properties of Ti43Al-xSiC did not change obviously when the amount of sic was 0.1wt% 0.3U 0.5wt%, but when the content of sic reached 0.9wt%, the microstructure and room temperature compressive properties of Ti43Al-xSiC did not change obviously. The microstructure of Ti43Al alloy with grain size of 105.99 渭 m is changed from coarse columnar structure to fine equiaxed structure. The compression strength of Ti47Al alloy was increased greatly at room temperature, and the compressive strength reached 1382.72 MPa. Compared with Ti43Al matrix alloy, the microstructure and properties of Ti47Al alloy were significantly increased by 64.14.SiC. When sic was added into Ti47Al, the content of sic increased with the increase of sic content. A fine rod reinforced Ti _ 2AlC phase was formed in the matrix, and a large number of Si-rich precipitates were dispersed at the grain boundaries. When the content of sic was 0.5 wt%, the compressive strength reached the maximum value of 2196.49 MPa, which increased 19.94% compared with the matrix alloy.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.23
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本文编号：2077105