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本文用普通透射电子显微镜研究了高质量氢化脱氢(HHDH)法Ti-6Al-4V粉末经不同温度热等静压(HIP)成型后的显微组织特征和性能。实验结果表明:显微组织的形态依赖于热等静压工艺。在β转变温度以下HIP时,显微组织是等轴晶粒;但是,在HIP温度为850℃时,等轴晶粒间可局部形成网状α片;等轴晶粒的尺寸也随着HIP温度的升高而变大。在β转变温度以上HIP时,则形成的显微组织是片状或者是针状晶,原始β晶界清晰可见。每个β晶粒内有几组平行排列的α集束,这些α片都具有几乎相同的结晶学取向。粉末中的氧含量和热等静压后的随炉冷却速度也影响合金的显微组织和性能。在缓慢冷却的情况下,可以形成沉淀产物,并首次发现在HHDH-Ti6Al-4V中也存在界面相。氧含量对显微组织的影响不太明显,然而对性能的影响却是可观的。含氧量低的粗粉试样,在950℃HIP成型可以得到较好的综合性能,而且可与熔锻的Ti-6Al-4V棒材相媲美。
In this paper, the microstructures and properties of Ti-6Al-4V powders prepared by high-temperature hydrogen-dehydrogenation (HHDH) method after hot isostatic pressing (HIP) were investigated by transmission electron microscopy. The experimental results show that the morphology of the microstructure depends on the hot isostatic pressing process. At HIP below the β-transformation temperature, the microstructure is equiaxed grains; however, at the HIP temperature of 850 ° C, reticular α-sheets are locally formed between the equiaxed grains; and the size of the equiaxed grains also increases with HIP The temperature increases and becomes larger. At HIP above the beta transus temperature, the microstructure formed is flaky or acicular and the original beta grain boundaries are clearly visible. There are several groups of α-bundles arranged in parallel within each β-grain, and these α-sheets all have almost the same crystallographic orientation. The oxygen content in the powder and the cooling rate of the furnace after hot isostatic pressing also affect the microstructure and properties of the alloy. In the case of slow cooling, a precipitated product can form, and for the first time it is found that there is also an interphase in HHDH-Ti6Al-4V. The effect of oxygen content on the microstructure is less pronounced, but the effect on the performance is considerable. Low oxygen content of the coarse powder sample, HIP molding at 950 ℃ can get better overall performance, and with the forged Ti-6Al-4V bar comparable.