Microstructure, precipitates and compressive properties of various holmium doped NiAl Cr(Mo, Hf) eutectic alloys
The microstructure and mechanical properties of NiAl-28Cr-6Mo-0.2Hf eutectic alloys with various holmium additions have been investigated by using of SEM, TEM and compression test. The results reveal that minor Ho addition could optimize the microstructure by refining the lamella inside of eutectic cell and controlling the coarsening of intercellular region. However the minor Ho addition results in the Ni_2Al_3Ho phase, which has hexagonal crystal structure and an orientation relationship with NiAl phase of )(Ni2AljHo)//[lll]_(NiA]) and (002)_(Ni2AljHo)//(l l'0)NjA1. Moreover the Ni17Ho2 phase is found in the Ni2Al3Ho phase, which has twin crystal inside and an orientation relationship with Ni2Al3Ho phase of [1 23]a1i7hO2//[1 24]Ni2AljHo and (11 )MnUoJ/(210)Ni;Al3Ho. In addition, the Ho addition promotes the precipitation of Ni2AlHf phase. More Ho addition coarsens the Cr(Mo) phases along the intercellular and results in more strengthening precipitates inside eutectic cell. When the Ho addition comes to 0.5 at.%, the alloy almost loses the cellular eutectic characteristic and exhibits a microstructure with coarse NiAl, massive Cr(Mo) and Ni2Al3Ho phases. The microstructure optimizations improve the mechanical properties of the alloy significantly, especially the alloy with 0.1 at.% Ho content.......
【作者名称】: Liyuan Sheng
, Lijun Wang
, Tingfei Xi
, Yufeng Zheng
, Hengqiang Ye
【作者单位】: Peking University, Beijing 100871, China ,PKU-HKUST ShenZhen-Hong Kong Institution, Shenzhen 518057, China
, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
, Peking University, Beijing 100871, China
, Peking University, Beijing 100871, China
, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
【关 键 词】: A. Intermetallics
, E. Mechanical properties
, F. Microstructure
【期刊名称】: Materials & design
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