Based on the Fe/C ultrafine particle obtained by means of laser pyrolysis method, a series of Fe-C-Mn ultrafine particle catalysts for F-T synthesis were prepared by adding certain amounts of Mn organic compounds to t...Based on the Fe/C ultrafine particle obtained by means of laser pyrolysis method, a series of Fe-C-Mn ultrafine particle catalysts for F-T synthesis were prepared by adding certain amounts of Mn organic compounds to the Fe/C UFP. XRD and TEM tests for the obtained catalysts showed that the active phases, α-Fe, Fe3Cand (Fe,Mn)O. were directly obtained. and that the particle size was in the range of 2-4 nm. The catalysts so obtained have stable structure, long life, high activity and selectivity for light olefins, especially for propylene. Testing of the crystal structure in the process of the reaction demonstrated the carbonide mechanism of FT synthesis and the presence of α-Fe, FexCy and (Fe, Mn)O, thus supporting the belief that these are the active phases.展开更多
The influence of hot deformation on the incubation period of ferrite transformation was calculated to determine the onset of deformation induced transformation. Temperature A r3d depends on deformation condition and a...The influence of hot deformation on the incubation period of ferrite transformation was calculated to determine the onset of deformation induced transformation. Temperature A r3d depends on deformation condition and alloying composition, and decreases with increasing carbon content. When deformation induced ferrite transformation occurs, the flow curves of dislocation density will show strong softening characteristic. Through temperature heavy deformation, ferrite transformation is enhanced and more volume fraction is obtained. The simulated results are in good agreement with the experiment ones.展开更多
A proper addition of Mn to Fe-C alloys could delay the isothermal transformation and change remarkably the TTT-curves to bay-like shape.The concentration of Mn at the α/γ interphase boundary and thir partition betwe...A proper addition of Mn to Fe-C alloys could delay the isothermal transformation and change remarkably the TTT-curves to bay-like shape.The concentration of Mn at the α/γ interphase boundary and thir partition between α- and γ- phase were measured by STEM/TEM-EDAX.The results show that the partition of Mn diminishes gradually as the reaction temperature decreases.There exists a certain temperature range with the strong- est Mn concentration spike at the interphase although no Mn partition is found between austenite and ferrite,and this temperature range is correspondent with the bay-temperature on TTT curves of the alloys.It is thus suggests that the change of TTT-curve configuration is due to the partition of alloy elements.The bay-like shape is attributed to the solute drag ef- fect and the solute drag-like effect caused by the enrichment of Mn at the α/γ interphase.展开更多
The thermodynamic database of the Fe C Mn-Si system has been developed in the framework of the CALPHAD approach. The sub-ternary systems have been carefully evaluated and revised based on available experimental data. ...The thermodynamic database of the Fe C Mn-Si system has been developed in the framework of the CALPHAD approach. The sub-ternary systems have been carefully evaluated and revised based on available experimental data. A satisfactory description of the liquid phase in the Fe C-Si system has been obtained. The C Mn Si system was assessed treating the liquid phase as a substitutional solution. Phase equilibria in the C- Mn-Si system, especially those involving the liquid phase, can be well described. Based on the extrapolation of the experimental data in the quaternary system, the Fe Mn Si system has been modified to agree well with experimental data at high temperatures. The comparison between the calculated and measured phase transformation tempera tures confirms the reliability of the present quaternary database. Additionally, the solidification process of Fe-0. 16C-1. 5Mn-1. 5Si （wt. %） alloy was simulated by using the thermodynamic database developed.展开更多
将C含量(质量分数)分别为0.05%和0.4%的Fe-C-Mn-Si钢进行等温处理得到贝氏体组织,采用EBSD技术对奥氏体共格孪晶界上形成的贝氏体铁素体变体进行分析.结果表明,2种钢中的贝氏体铁素体与母相奥氏体均成近似K-S取向关系.奥氏体孪晶界两侧...将C含量(质量分数)分别为0.05%和0.4%的Fe-C-Mn-Si钢进行等温处理得到贝氏体组织,采用EBSD技术对奥氏体共格孪晶界上形成的贝氏体铁素体变体进行分析.结果表明,2种钢中的贝氏体铁素体与母相奥氏体均成近似K-S取向关系.奥氏体孪晶界两侧形成取向相同的变体对.此变体对形成后,孪晶界基本不再显现.晶体学分析表明,共格孪晶界两侧可能出现的变体对最多不超过3组,且这3组变体对的惯习面均与孪晶界平行,因此,贝氏体铁素体变体都将沿孪晶界生长.含C量为0.05%的Fe-C-Mn-Si钢中奥氏体孪晶界上只观察到一组贝氏体铁素体变体对的形成,这是因为C含量较低,贝氏体铁素体生长速度较快,消除了其它变体对的形核机会,先形核的变体对一旦形核就迅速覆盖整个孪晶面.而在含C量为0.4%的Fe C Mn-Si钢中,由于C含量较高,贝氏体铁素体生长速度较慢,3组变体对均有机会形核,因此,在孪晶界上可以观察到这3组变体对同时出现.展开更多
Warm deformation tests were performed using a kind of tubby heater. The microstructures and mechanical properties of an Fe-C-Mn-Si multiphase steel resulting from different warm deformation temperatures were investiga...Warm deformation tests were performed using a kind of tubby heater. The microstructures and mechanical properties of an Fe-C-Mn-Si multiphase steel resulting from different warm deformation temperatures were investiga- ted by using LOM （light optical microscopy）, SEM and XRD. The results indicated that the microstructure contai- ning polygonal ferrite, granular bainite and a significant amount of the stable retained austenite can be obtained through hot deformation and subsequent austempering. Warm deformation temperature affects the mechanical prop- erties of the hot rolled TRIP steels. Ultimate tensile strength balance reached maximum （881 MPa） when the speci- men was deformed at 250 ~C, and the total elongation and strength-ductility reached maximum （38% and 28 614 MPa ~ ~, respectively） at deforming temperature of 100 ~C. Martensite could nucleate when austenite was deformed above M~, because mechanical driving force compensates the decrease of chemical driving force. The TRIP effect occurs in the Fe-C-Mn-Si multiphase steel at deforming temperature ranging from 15 to 350 ~C. The results of the effects of warm deformation on the mechanical properties of the Fe-C-Mn-Si multiphase steel can provide theoretical basis for the ap- plications and the warm working of the hot rolled TRIP sheet steels in industrial manufacturing.展开更多
文摘Based on the Fe/C ultrafine particle obtained by means of laser pyrolysis method, a series of Fe-C-Mn ultrafine particle catalysts for F-T synthesis were prepared by adding certain amounts of Mn organic compounds to the Fe/C UFP. XRD and TEM tests for the obtained catalysts showed that the active phases, α-Fe, Fe3Cand (Fe,Mn)O. were directly obtained. and that the particle size was in the range of 2-4 nm. The catalysts so obtained have stable structure, long life, high activity and selectivity for light olefins, especially for propylene. Testing of the crystal structure in the process of the reaction demonstrated the carbonide mechanism of FT synthesis and the presence of α-Fe, FexCy and (Fe, Mn)O, thus supporting the belief that these are the active phases.
文摘The influence of hot deformation on the incubation period of ferrite transformation was calculated to determine the onset of deformation induced transformation. Temperature A r3d depends on deformation condition and alloying composition, and decreases with increasing carbon content. When deformation induced ferrite transformation occurs, the flow curves of dislocation density will show strong softening characteristic. Through temperature heavy deformation, ferrite transformation is enhanced and more volume fraction is obtained. The simulated results are in good agreement with the experiment ones.
文摘A proper addition of Mn to Fe-C alloys could delay the isothermal transformation and change remarkably the TTT-curves to bay-like shape.The concentration of Mn at the α/γ interphase boundary and thir partition between α- and γ- phase were measured by STEM/TEM-EDAX.The results show that the partition of Mn diminishes gradually as the reaction temperature decreases.There exists a certain temperature range with the strong- est Mn concentration spike at the interphase although no Mn partition is found between austenite and ferrite,and this temperature range is correspondent with the bay-temperature on TTT curves of the alloys.It is thus suggests that the change of TTT-curve configuration is due to the partition of alloy elements.The bay-like shape is attributed to the solute drag ef- fect and the solute drag-like effect caused by the enrichment of Mn at the α/γ interphase.
基金the financial support from the Chinese National Key Project of Science and Technology (Grant No. 2012ZX06004-012)the support from the Chinese Scholarship Council (CSC)the support from the Shanghai Municipal Science and Technology Commission (Grant No. 15DZ2260300,15DZ2260301)
文摘The thermodynamic database of the Fe C Mn-Si system has been developed in the framework of the CALPHAD approach. The sub-ternary systems have been carefully evaluated and revised based on available experimental data. A satisfactory description of the liquid phase in the Fe C-Si system has been obtained. The C Mn Si system was assessed treating the liquid phase as a substitutional solution. Phase equilibria in the C- Mn-Si system, especially those involving the liquid phase, can be well described. Based on the extrapolation of the experimental data in the quaternary system, the Fe Mn Si system has been modified to agree well with experimental data at high temperatures. The comparison between the calculated and measured phase transformation tempera tures confirms the reliability of the present quaternary database. Additionally, the solidification process of Fe-0. 16C-1. 5Mn-1. 5Si （wt. %） alloy was simulated by using the thermodynamic database developed.
文摘将C含量(质量分数)分别为0.05%和0.4%的Fe-C-Mn-Si钢进行等温处理得到贝氏体组织,采用EBSD技术对奥氏体共格孪晶界上形成的贝氏体铁素体变体进行分析.结果表明,2种钢中的贝氏体铁素体与母相奥氏体均成近似K-S取向关系.奥氏体孪晶界两侧形成取向相同的变体对.此变体对形成后,孪晶界基本不再显现.晶体学分析表明,共格孪晶界两侧可能出现的变体对最多不超过3组,且这3组变体对的惯习面均与孪晶界平行,因此,贝氏体铁素体变体都将沿孪晶界生长.含C量为0.05%的Fe-C-Mn-Si钢中奥氏体孪晶界上只观察到一组贝氏体铁素体变体对的形成,这是因为C含量较低,贝氏体铁素体生长速度较快,消除了其它变体对的形核机会,先形核的变体对一旦形核就迅速覆盖整个孪晶面.而在含C量为0.4%的Fe C Mn-Si钢中,由于C含量较高,贝氏体铁素体生长速度较慢,3组变体对均有机会形核,因此,在孪晶界上可以观察到这3组变体对同时出现.
基金Sponsored by National Natural Science Foundation of China (50334010)
文摘Warm deformation tests were performed using a kind of tubby heater. The microstructures and mechanical properties of an Fe-C-Mn-Si multiphase steel resulting from different warm deformation temperatures were investiga- ted by using LOM （light optical microscopy）, SEM and XRD. The results indicated that the microstructure contai- ning polygonal ferrite, granular bainite and a significant amount of the stable retained austenite can be obtained through hot deformation and subsequent austempering. Warm deformation temperature affects the mechanical prop- erties of the hot rolled TRIP steels. Ultimate tensile strength balance reached maximum （881 MPa） when the speci- men was deformed at 250 ~C, and the total elongation and strength-ductility reached maximum （38% and 28 614 MPa ~ ~, respectively） at deforming temperature of 100 ~C. Martensite could nucleate when austenite was deformed above M~, because mechanical driving force compensates the decrease of chemical driving force. The TRIP effect occurs in the Fe-C-Mn-Si multiphase steel at deforming temperature ranging from 15 to 350 ~C. The results of the effects of warm deformation on the mechanical properties of the Fe-C-Mn-Si multiphase steel can provide theoretical basis for the ap- plications and the warm working of the hot rolled TRIP sheet steels in industrial manufacturing.
