材料科学
微观结构
等轴晶
电子背散射衍射
退火(玻璃)
粒度
合金
复合材料
均质化(气候)
晶粒生长
再结晶(地质)
冶金
各向同性
各向异性
生物多样性
生态学
古生物学
物理
量子力学
生物
作者
Alessandro Carrozza,Alberta Aversa,Federico Mazzucato,Emilio Bassini,Diego Manfredi,Sara Biamino,Anna Valente,Paolo Fino
标识
DOI:10.1016/j.matchar.2022.111958
摘要
This work deals with the effect of different heat treatments on directed energy deposition (DED)-produced Ti-6Al-4V samples. Annealing treatments at 1050 °C followed by different cooling rates were conducted to allow a complete recrystallization of the microstructure and remove the columnar prior-β grains, thus increasing the overall isotropy of the material. An agine treatment at 540 °C was also performed for further microstructural stabilization. The microstructures, textures and mechanical properties were then assessed. Due to the heat treatments, greatly differing microstructures were achieved in an equiaxed grain morphology. However, a “grain memory” effect was detected which resulted in the grains size increasing along the height of the samples. This effect was correlated to the intrinsic prior-β grain width variation along Z on the as-printed specimens, typical of the DED technology. Electron backscatter diffraction analyses proved that the intensity of the preferential directions increased after the heat treatments, likely due to the crystallographic variant selection mechanisms taking place when the samples cool down from the annealing temperature. This effect is also influenced by the significant difference in terms of prior-β grains sizes between the heat-treated and the as-printed specimens. To sum up, a complete homogenization of the material via heat treatment above the β-transus temperature proved to be challenging. In fact, the data suggest that the intrinsic texture-related anisotropy granted by the manufacturing process is very difficult to be eliminated. • The post-annealing cooling mean has a great impact on the final microstructure. • “Grain memory” effect prevents full prior-β grains homogenization. • Comparing the texture of different microstructures is hard due to the dissimilar sizes. • Crystallographic variant selection mechanisms take place during the heat treatment.
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