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本实验采用真空非自耗电弧熔炼法制备了含C量不同的Nb-20Ti-16Al合金,C元素添加含量为0、1at.%和10at.%,而后在1100℃下进行不同时间的热处理。通过X射线衍射分析(XRD),扫描电子显微镜(SEM)和电子探针(EPMA)观察合金的组织。合金的高温压缩强度在gleeble-3800上进行,应变速率为10-2 s-1,测试温度为1100℃。室温断裂韧性在显微维氏硬度计上通过压痕法进行。实验结果表明,铸态合金在1100℃热处理过程中,Nb-20Ti-16Al合金中过饱和Nbss(铌基固溶体)发生了分解,即发生了Nbss→Nbss+Nb3Al反应;而添加了C元素的合金中,在Nb3Al析出的同时,碳化物发生了分解,反应可表示为Nbss+(Nb,Ti)C→Nbss+Nb3Al。随着保温时间的延长,Nb3Al的尺寸和体积分数增加,而Nbss的体积分数减小。C元素的添加能够使Nbss和Nb3Al的晶格常数减小,表明C原子主要以置换原子的形式固溶于Nbss和Nb3Al中。随着C元素的增加,热处理后的合金Nbss体积分数减小,高温压缩强度增加,而室温断裂韧性下降。
In this experiment, Nb-20Ti-16Al alloy with different content of C was prepared by vacuum non-consumable arc melting method. The content of element C was 0, 1at.% And 10at.%, And then heat treated at 1100 ℃ for different time . The alloy structure was observed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe (EPMA). The high temperature compressive strength of the alloy was measured on a gleeble-3800 with a strain rate of 10-2 s-1 and a test temperature of 1100 ° C. Room temperature fracture toughness is measured on a micro Vickers hardness tester by the indentation method. The experimental results show that the Nbss → Nbss + Nb3Al reaction takes place in the as-cast Nb-20Ti-16Al alloy during the heat treatment at 1100 ℃, whereas the addition of the C-element alloy , The carbides decompose during the precipitation of Nb3Al, and the reaction can be expressed as Nbss + (Nb, Ti) C → Nbss + Nb3Al. As the holding time prolongs, the size and volume fraction of Nb3Al increase while the volume fraction of Nbss decreases. The addition of C element can reduce the lattice constants of Nbss and Nb3Al, indicating that the C atoms mainly dissolve in Nbss and Nb3Al in the form of substitutional atoms. With the increase of C element, the Nbss volume fraction of heat-treated alloy decreases, the compressive strength at high temperature increases, while the fracture toughness at room temperature decreases.