Microstructural evolution and mechanical properties of rapidly solidified Ni-Ge alloys

被引：0
|
作者：
Yan P. [1 ]
Wang W. [1 ]
Yan N. [1 ]
Sha S. [1 ]
Wei B. [1 ]
机构：
[1] School of Physical Science and Technology, Northwestern Polytechnical University, Xi'an
来源：
Zhongguo Kexue Jishu Kexue/Scientia Sinica Technologica | 2020年 / 50卷 / 08期
关键词：
Dendritic growth; Eutectic growth; Plastic deformation; Rapid solidification; Yield strength;
D O I：
10.1360/SST-2020-0022
中图分类号：
学科分类号：
摘要：
Structural evolution and mechanical performances of rapidly solidified Ni95Ge5 and Ni33Ge67 alloys were investigated under two conditions involving drop-tube containerless processing and copper-mold injection casting. As the cooling rate increased, the coarse dendritic structure of the primary (Ni) phase for Ni95Ge5 alloy changed to equiaxed grains structure, and the microstructure of Ni33Ge67 alloy showed a transition from coarse (NiGe + Ge) eutectic to refined structure plus some primary Ge phase. Containerless processing can produce finer microstructures than those of injection casting owing to higher cooling rate. Nanoindentation measurements indicated that both alloys showed a remarkable enhancement of Vickers hardness along with the microstructural evolution, and the hardening mechanism for a single-phase alloy was found to be grain-boundary strengthening, while that of the eutectic alloy was attributed to the multiphase coordinated strengthening. The strain hardening exponents of Ni95Ge5 and Ni33Ge67 alloys were calculated as 0.28 and 0.77, respectively. The special morphology evolution and lower strain hardening exponent of Ni95Ge5 alloy remarkably improved the hardening ability. Its hardness increased up to 56.6% that was much higher than the eutectic alloy. Moreover, these alloys displayed different relations between hardness and strength. The average ratio of hardness to strength for Ni95Ge5 alloy was 2.75, while that for Ni33Ge67 alloy was 9.09. Both the experimental evidence and theoretical analysis revealed that obvious enhancements of hardness and strength were achieved using a high cooling rate; thus, the drop-tube processed alloy particles showed better mechanical properties than those of the as-cast alloys owing to their higher cooling rates. It is obvious that rapid solidification conditions can improve the mechanical properties of both the alloys to various degrees. © 2020, Science Press. All right reserved.
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页码：1042 / 1054
页数：12
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