Xinghao DU
,
Jianting GUO
,
Bide ZHOU
,
Liangyue XIONG
材料科学技术（英）
In order to study the subboundaries evolution in superplastically deformed NiAl, the positron lifetime change during superplastic deformation process was measured. It is shown that the superplastic deformation of NiAl has not influence on its τ2, the newly recrystallized grain boundaries formed during entire superplastic deformation process belong to the calegory of subboundaries and have not contribution to the superplastic strain.
关键词:
NiAl
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Xinghao DU
,
Jianting GUO
材料科学技术（英）
A multiphase NiAl-28Cr-5.85Mo-0.15Hf alloy, which was directionally solidified (DS) in an Al2O3-SiO2 mold by standard Bridgman method and then underwent prolonged solution and aging treatment was prepared. The microstructure, tensile properties as well as tensile creep of the heat-treated alloy at different temperatures were studied. The alloy was composed of NiAl, Cr(Mo) and Hf-rich phase and small amount of fine Heusler phase (Ni2AlHf). Although the present alloy exhibited high tensile strength at low temperature, it was weaker than that of system with high content Hf but still stronger than that of many NiAl-based alloys at high temperatures. The fracture toughness is lower than that of DS NiAl-28Cr-6Mo alloy. Nevertheless, advantageous effects on the mechanical properties, $i.e$. the decrease in brittle-to-ductile transition temperature (BDTT) were obtained for the low content of Hf. The obtained creep curves exhibit conventional shape: a short primary creep and long accelerated creep stages. The rupture properties of the heat-treated alloy follow the Monkman-Grant relationship, which exhibits similar creep behavior to that of NiAl/Cr(Mo) system with high Hf content.
关键词:
NiAl/Cr(Mo
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