The influence of Hf on the precipitation behavior of γ'phase and the subsequent tensile properties of a Ni-Cr-Mo alloy after long-term thermal exposure was investigated.The results reveal that the addition of Hf ...The influence of Hf on the precipitation behavior of γ'phase and the subsequent tensile properties of a Ni-Cr-Mo alloy after long-term thermal exposure was investigated.The results reveal that the addition of Hf increases the average diameter ofγ'phases after thermal exposure at 700℃ for 5000 h,which enhances the critical resolved shear stress required for dislocations to shear the γ'phases in the Ni-Cr-Mo alloy.Simultaneously,element Hf incorporated into the γ'phases increases the lattice mismatch between the γ'and γ phase,thereby strengthening the coherency strengthening effect.These two factors collectively contribute to the enhanced strength of the alloy.Thus,Hf alloying effectively improves the yield strength of the Ni-Cr-Mo alloy after thermal exposure at 700℃.展开更多
Using the slurry reaction sintering process to prepare Hf-Ta-Si composite coating on Ta12W alloy surface,the effect of Si content on the in-situ formation mechanism of the Hf-Ta-Si coating was investigated.Results sho...Using the slurry reaction sintering process to prepare Hf-Ta-Si composite coating on Ta12W alloy surface,the effect of Si content on the in-situ formation mechanism of the Hf-Ta-Si coating was investigated.Results show that 30Hf:70Si coatings exhibit inferior surface uniformity with some pores.The upper part of the sample displays a four-layer gradient structure:the outermost layer is primarily composed of HfSi and HfC,the middle layer consists of(Ta,Hf)_(5)Si_(3)solid solution,the lower main-layer consists of TaSi_(2),and the coating/substrate interface layer is Ta_(5)Si_(3).However,the flow of molten Si under gravity leads to Si-enrichment on the lower part of the coating.After optimizing the Hf:Si ratio to 40:60,the gradient differences in elemental distribution on the coating surface decrease.The surface layer is dominated by HfSi/HfC,but the precipitation of HfC becomes more uniform.The continuity of the(Ta,Hf)_(5)Si_(3)solid solution in middle layer is enhanced,whereas the lower layer and the interface transition layer remain unchanged.Overall,a denser multi-layer gradient structure is formed with improved surface uniformity.Additionally,the acid-alcohol resin in the organic solvent suffers high-temperature pyrolysis and in-situ reacts with Hf to generate the ultra-high-temperature ceramic HfC.This phenomenon is expected to enhance the oxidation resistance and high-temperature stability of coating.展开更多
基金National Key Research and Development Program of China(2021YFB3704103)National Natural Science Foundation of China(51571191)。
文摘The influence of Hf on the precipitation behavior of γ'phase and the subsequent tensile properties of a Ni-Cr-Mo alloy after long-term thermal exposure was investigated.The results reveal that the addition of Hf increases the average diameter ofγ'phases after thermal exposure at 700℃ for 5000 h,which enhances the critical resolved shear stress required for dislocations to shear the γ'phases in the Ni-Cr-Mo alloy.Simultaneously,element Hf incorporated into the γ'phases increases the lattice mismatch between the γ'and γ phase,thereby strengthening the coherency strengthening effect.These two factors collectively contribute to the enhanced strength of the alloy.Thus,Hf alloying effectively improves the yield strength of the Ni-Cr-Mo alloy after thermal exposure at 700℃.
基金National Natural Science Foundation of China(52071274)Natural Science Foundation of Shaanxi Province of China(2025JC-YBMS-466)+1 种基金Key Research and Development Projects of Shaanxi Province(2023-YBGY-442)Science and Technology Nova Project-Innovative Talent Promotion Program of Shaanxi Province(2020KJXX-062)。
文摘Using the slurry reaction sintering process to prepare Hf-Ta-Si composite coating on Ta12W alloy surface,the effect of Si content on the in-situ formation mechanism of the Hf-Ta-Si coating was investigated.Results show that 30Hf:70Si coatings exhibit inferior surface uniformity with some pores.The upper part of the sample displays a four-layer gradient structure:the outermost layer is primarily composed of HfSi and HfC,the middle layer consists of(Ta,Hf)_(5)Si_(3)solid solution,the lower main-layer consists of TaSi_(2),and the coating/substrate interface layer is Ta_(5)Si_(3).However,the flow of molten Si under gravity leads to Si-enrichment on the lower part of the coating.After optimizing the Hf:Si ratio to 40:60,the gradient differences in elemental distribution on the coating surface decrease.The surface layer is dominated by HfSi/HfC,but the precipitation of HfC becomes more uniform.The continuity of the(Ta,Hf)_(5)Si_(3)solid solution in middle layer is enhanced,whereas the lower layer and the interface transition layer remain unchanged.Overall,a denser multi-layer gradient structure is formed with improved surface uniformity.Additionally,the acid-alcohol resin in the organic solvent suffers high-temperature pyrolysis and in-situ reacts with Hf to generate the ultra-high-temperature ceramic HfC.This phenomenon is expected to enhance the oxidation resistance and high-temperature stability of coating.
文摘随着微电子技术的不断发展,MOSFET 的特征尺寸已缩小至100nm 以下,SiO_2作为栅介质材料已不能满足技术发展的需求,因此必须寻求一种新型高 K 的介质材料来取代 SiO_2。当今普遍认为 Hf 基栅介质材料是最有希望取代 SiO_2而成为下一代 MOSFET 的栅介质材料。综述了高 K 栅介质材料的意义、Hf 基高 K 栅介质材料的最新研究进展和 Hf 基高 K 栅介质材料在克服自身缺陷时使用的一些技术;介绍了一款由 Hf 基高 K 介质材料作为栅绝缘层制作的 MOSFET。
