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Microstructure and Mechanical Properties of Powder Metallurgical TiAl-Based Alloy Made by Micron Bimodal-Sized Powders
Journal of Materials Engineering and Performance ( IF 2.3 ) Pub Date : 2020-11-23 , DOI: 10.1007/s11665-020-05342-3
Yibo Ren , Ying Han , Shun Yan , Jiapeng Sun , Zhenxin Duan , Hua Chen , Xu Ran

Three powder metallurgical Ti-48Al-2Cr-2Nb compacts were prepared using spherical pre-alloyed powders, mechanically milled powders, and a mixture of the spherical pre-alloyed powders and the mechanical milled powders in a weight ratio of 1:4. Different microstructures corresponding to coarse grains, ultrafine grains, and bimodal-size grains, respectively, were obtained. The compact with a bimodal grain structure exhibits a good combination of high-yield compressive strength (~ 1393 MPa) and improved compression ratio to fracture (~ 13.9%) at room temperature due to the effects of back-stress and ductile γ-TiAl single-phase layer generated near the ultrafine/coarse grain interface. At high temperatures, the compressive properties of the compact with the bimodal grain size distribution are sensitive to the temperature. A relatively high deformation resistance is achieved at 750 °C. At this temperature, the coarse grain region of the bimodal grain-sized microstructure undergoes more strain, and the dynamic recrystallization is promoted with increasing strain, improving the ductility. By contrast, the ultrafine grains in the bimodal grain size microstructure dominate the dynamic softening when the temperature is higher than 850 °C due to their accelerated dynamic recrystallization and easy grain boundary slip that are responsible for the good formability and the sharp decrease in deformation resistance of this alloy.



中文翻译:

微米双峰粉末制备的粉末冶金TiAl基合金的组织和力学性能

使用球形预合金粉末,机械研磨的粉末以及球形预合金粉末和机械研磨粉末的重量比为1:4的混合物制备了三种粉末冶金Ti-48Al-2Cr-2Nb压块。获得了分别对应于粗晶粒,超细晶粒和双峰尺寸晶粒的不同微观结构。由于背应力和延性γ的影响,具有双峰晶粒结构的压块在室温下表现出高屈服抗压强度(〜1393 MPa)和断裂压缩比(〜13.9%)的良好组合。-TiAl单相层在超细/粗晶粒界面附近产生。在高温下,具有双峰粒度分布的压坯的压缩特性对温度敏感。在750°C下可获得相对较高的抗变形性。在此温度下,双峰晶粒大小组织的粗晶粒区域承受更大的应变,并且随着应变的增加而促进了动态再结晶,从而改善了延展性。相比之下,当温度高于850°C时,双峰晶粒尺寸微结构中的超细晶粒占主导地位,这归因于其加速的动态再结晶和易发生的晶界滑移,这导致良好的可成形性和抗变形性急剧下降。这种合金。

更新日期:2020-11-25
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