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| 1 | Strengthening FCC-CoCrFeMnNi high entropy alloys by Mo addition显示文摘In order to strengthen the face-centered-cubic(FCC) type CoCrFeMnNi high entropy alloys(HEAs), different contents of Mo(0–16 at.%, similarly hereinafter) were alloyed. Phase evolution, microstructure,mechanical properties and related mechanism of these HEAs were systematically studied. The results show that sigma phase is appeared with addition of Mo, and the volume fraction of it increases gradually from 0 to 66% with increasing Mo content. It is found that Mo is enriched in sigma phase, which indicates that Mo element is beneficial to form sigma phase. Compressive testing shows that the yield strength of the alloys increases gradually from 216 to 765 MPa, while the fracture strain decreases from 50%(no fracture) to 19% with increasing of Mo. The alloy exhibits the best compressive performance when Mo content reaches 11%, the yield strength, fracture strength and fracture strain are 547 MPa, 2672 MPa and44% respectively. The increased volume fraction of sigma phase plays an important role in improving the compressive strength of(CoCrFeMnNi)_(100-x)Mo_xHEAs. | Gang Qin Ruirun Chen Huiting Zheng Hongze Fang Liang Wang Yanqing Su Jingjie Guo Hengzhi Fu | 2019 | Journal of Materials Science & Technology2019，35，4： | 11 |
| 2 | NbMoTiVSi_(x) refractory high entropy alloys strengthened by forming BCC phase and silicide eutectic structure显示文摘In order to improve mechanical properties of refractory high entropy alloys,silicide was introduced and NbMoTiVSi_(x)(x=0,0.1,0.2,0.3,and 0.4,molar ratio) refractory high entropy alloys are prepared by vacuum arc melting.Phase composition,micro structure evolution and mechanical properties were systematically studied.Results show that the silicide phase is formed in the alloys with addition of silicon,and the volume fraction of silicide increases from 0 to 8.3 % with increasing of silicon.Microstructure observation shows that the morphology of dendrite changes from columnar to near equiaxed,eutectic structure is formed at grain boundaries and composed of secondary BCC phase and silicide phase.The average length of the primary and second dendrites decreases with the increasing of silicon.Whereas,the ratio of eutectic structure increases from 0 to 19.8 % with the increment of silicon.The refinement of microstructure is caused by heterogeneous nucleation from the silicide.Compressive tests show that the yield and ultimate strength of the alloys increases from 1141.5 MPa to 2093.1 MPa and from 1700.1 MPa to 2374.7 MPa with increasing silicon content.The fracture strain decreases from 24.7 %-11.0 %.Fracture mechanism is changed from ductile fracture to ductile and brittle mixed fracture.The improvement of the strength is caused by grain bounda ry strengthening,which includes more boundaries around primary BCC phase and eutectic structure in grain boundary,both of them is resulted from the formation of silicide. | Qin Xu Dezhi Chen Chongyang Tan Xiaoqin Bi Qi Wang Hongzhi Cui Shuyan Zhang Ruirun Chen | 2021 | Journal of Materials Science & Technology2021，，1： | 9 |
| 3 | Microstructures and mechanical properties of Nb-alloyed CoCrCuFeNi high-entropy alloys显示文摘Nb has a positive effect on improving the mechanical properties of metal materials, and it is expected to strengthen CoCrCuFeNi high-entropy alloys(HEAs) with outstanding ductility and relatively weak strength. In this paper, the alloying effects of Nb on the microstructural evolution and the mechanical properties of the(CoCrCuFeNi)_(100-x)Nb_xHEA were investigated systematically. The result shows that Nb promotes the phase transition from FCC(face-centered cubic) to Laves phase, and the volume fractions of Laves phase increase from 0% to 58.2% as the Nb content increases. Compressive testing shows that the addition of Nb has a positive effect on improving the strength of CoCrCuFeNi HEA. The compressive yield strength of(CoCrCuFeNi)_(100-x)Nb_xHEAs increases from 338 MPa to 1322 MPa and the fracture strain gradually reduces from 60.0%(no fracture) to 8.1% as the Nb content increases from 0 to 16 at.%. The volume fraction increase of hard Laves phase is the key factor for the strength increase, and the reduction of the VEC(valence electron concentration) value induced by the addition of Nb is beneficial for the increase of the Laves phase content in these alloys. | Gang Qin Shu Wang Ruirun Chen Xue Gong Liang Wang Yanqing Su Jingjie Guo Hengzhi Fu | 2018 | Journal of Materials Science & Technology2018，34，2： | 8 |
| 4 | Lamellar orientation control in directionally solidified TiAl intermetallics显示文摘TiAl-based alloys are potentially used as high-temperature structural materials with a high specific strength in the range of^900°C.However,the mechanical properties of TiAl-based alloys are extremely anisotropic with respect to the lamellar orientation of the microstructures.A balance combination of room-temperature ductility and strength can be achieved when the lamellar orientation are aligned parallel to the tensile stress direction.Lamellar orientation control of TiAl-based alloys by directional solidification technique has been widely studied in recent years.Two different directional solidification processes can be used to modify the lamellar orientation.One is a seeding technique and the other is adjusting the solidification path.This paper reviews the principles of the two methods and their progress.The influence of alloy composition and solidification parameters on lamellar orientation control is also discussed. | Su Yanqing Liu Tong Li Xinzhong Chen Ruirun Ding Hongsheng Guo Jingjie Fu Hengzhi | 2014 | China Foundry2014，11，4： | 7 |
| 5 | Numerical simulation of electro-magnetic and flow fields of TiAl melt under electric field显示文摘This article aims at building an electromagnetic and fluid model, based on the Maxwell equations and Navier-Stokes equations, in TiAl melt under two electric fields.FEM (Finite Element Method) and APDL (ANSYS Parametric Design Language) were employed to perform the simulation, model setup, loading and problem solving.The melt in molds of same cross section area with different flakiness ratio (i.e.width/depth) under the load of sinusoidal current or pulse current was analyzed to obtain the distribution of electromagnetic field and flow field.The results show that the induced magnetic field occupies sufficiently the domain of the melt in the mold with a flakiness ratio of 5:1.The melt is driven bipolarly from the center in each electric field.It is also found that the pulse electric field actuates the TiAl melt to flow stronger than what the sinusoidal electric field does. | Zhang Yong Ding Hongsheng Jiang Sanyong Chen Ruirun Guo Jingjie | 2010 | China Foundry2010，7，3： | 6 |
| 6 | Influences of pulse electric current treatment on solidification microstructures and mechanical properties of Al-Si piston alloys显示文摘Three kinds of Al-Si piston alloys were prepared and subjected to pulse electric current treatment (PECT)at different pouring temperatures.Some aspects of the solidification microstructures were examined including the morphology and the distribution of the matrix and the secondary phases by using of optical microscopy(OM),SEM and EDS methods.Results indicate that PECT can refine the grains of a-Al in the alloys as effectively as chemical modification by sodium salt.The processing parameters of PECT on the multi-component Al-Si alloys were then optimized through the testing of tensile strength,elongation and microhardness of the prepared alloys.A new theory was put forward to explain the mechanism of PECT. | Ding Hongsheng Zhang Yong Jiang Sanyong Chen Ruirun Zhao Zhilong Guo Jingjie Xu Daming Fu Hengzhi | 2009 | China Foundry2009，6，1： | 6 |
| 7 | An innovative method for the microstructural modification of TiAl alloy solidified via direct electric current application显示文摘Ti-48Al-2Cr-2Nb alloy solidified with the application of direct electric current has a refined and homogeneous microstructure without segregation. We observed an initial decrease followed by a subsequent increase in grain size and lamellar spacing, with the increase in current density. Similar trend can also be obtained by varying the amount of α2-phase(Ti_3Al). Using a directional solidification processing method,the columnar crystal microstructure transforms into an equiaxed crystal microstructure at a current density of 32–64 m A/mm^2. High dislocation density is also introduced with a minimum cross-sectional grain size of 460 μm at a current density of 64 mA/mm^2. The application of electric current alters the free energy of the critical nucleus and temperature via joule heating, causing a transformation from a columnar grain microstructure into an equiaxed grain microstructure. The increase in current density leads to a rise of the nucleation rate, and a resulting undercooling combined with temperature gradient contribute to growth of the primary phase, which finally results in grain coarsening at a critical current density of 96 mA/mm^2.The climb and cross-slip of dislocation and the migration of grain boundary ultimately create variable lamellae spacing of TiAl alloy. | Zhanxing Chen Hongsheng Ding Ruirun Chen Shiqiu Liu Jingjie Guo Hengzhi Fu | 2019 | Journal of Materials Science & Technology2019，35，1： | 5 |
| 8 | Characterization of zirconia-based slurries with different binders for titanium investment casting显示文摘The materials and physical properties of primary slurry are crucial to the surface quality of the finished castings,especially for high reactivity titanium alloys.The aim of this study is to investigate the influence of different binders on the physical properties of primary slurry for titanium alloy investment casting.The zirconia-based slurries with different binders were evaluated by comparing the parameters:viscosity,bulk density,plate weight, suspensibility,gel velocity and strength.The results indicate that a higher viscosity of binder leads to a higher viscosity and suspensibility of slurry with the same powder/binder ratio.The retention rate and thickness of primary layer increase with an increase in the viscosity of the slurry,and a higher retention rate is associated with a thicker primary layer.The gel velocity of the slurry is correlated with the gel velocity of the binder.The green strength and the baked strength of the primary layer are determined by the properties of the binder after gel and by the production of the binder after fired,respectively. | Zhao Ertuan Kong Fantao Chen Yanfei Chen Ruirun Chen Yuyong | 2012 | China Foundry2012，9，2： | 4 |
| 9 | Electromagnetic characteristics of square cold crucible designed for silicon preparation显示文摘In the present work,the strength and distribution of electromagnetic field in the square cold crucible that designed for casting multicrystalline silicon were measured and analyzed by using a small coil method.The results show that in the perpendicular direction the maximum of magnetic flux density(B) appears at the position slightly above the middle of the coil,and then B attenuates toward both sides,and decreases more to the bottom of the crucible.In the horizontal direction,from the edge(corner) to the center,B firstly decreases gradually,and then slightly increases in the center.While along the inner sides of the crucible,the distribution is relatively uniform,especially in the effective acting range.B increases with the increasing of the input power.Moving the coil to the top of the crucible,B increases and the effective acting range of the electromagnetic field becomes bigger.For the coils with different turns,the five turns coil can induce the highest magnetic flux density. | Chen Ruirun Huang Feng Guo Jingjie Ding Hongsheng Yang Jieren Fu Hengzhi | 2011 | China Foundry2011，8，2： | 3 |
| 10 | Effect of power parameter and induction coil on magnetic field in cold crucible during continuous melting and directional solidification显示文摘Bottomless electromagnetic cold crucible is a new apparatus for continuous melting and directional solidification;however,improving its power efficiency and optimizing the configuration are important for experiment and production.In this study,a 3-D finite element (FE) method based on experimental verification was applied to calculate the magnetic flux density (Bz).The effects of the power parameters and the induction coil on the magnetic field distribution in the cold crucible were investigated.The results show that higher current intensity and lower frequency are beneficial to the increase of Bz at both the segment midpoint and the slit location.The induction coil with racetrack section can induce greater Bz,and a larger gap between the induction coil and the shield ring increases Bz.The mechanism for this effect is also discussed. | Chen Ruirun Yang Jieren Ding Hongsheng Huang Feng Su Yanqing Guo Jingjie Fu Hengzhi | 2012 | China Foundry2012，9，1： | 2 |
| 11 | Twin and twin intersection phenomena in a creep deformed microalloyed directionally solidified high Nb containing TiAl alloy显示文摘The creep behavior of a directionally solidified TiAl alloy with a high Nb content after microalloying by the addition of small amounts of W,Cr,and B elements was investigated by scanning electron microscopy and transmission electron microscopy.By means of directional solidification and microalloying,a TiAl alloy with a fine and uniform microstructure and continuous columnar crystals was obtained.High-density dislocations,deformation nanotwins,and twin intersections were observed inγlamellae.The results show that,in comparison with the ternary TiAl alloy,the microalloyed high Nb containing TiAl alloy exhibited better creep properties at 760℃and 275 MPa.The decrease in stacking fault energy can promote dislocation dissociation and the formation of deformation twins,and the twin intersections can hinder the movement of dislocation to enhance the creep performance of the TiAl alloy. | Xuesong Xu Hongsheng Ding Haitao Huang He Liang Hao Guo Ruirun Chen Jingjie Guo Hengzhi Fu | 2022 | Journal of Materials Science & Technology2022，，32： | 2 |
| 12 | Enhanced strength and ductility in Ti46Al4Nb1Mo alloys via boron addition显示文摘To improve the strength and ductility of Ti Al alloys by second phase, Ti46 Al4 Nb1 Mo alloys doped with different B content(0.4%, 0.8%, 1.2%, 1.6% and 2.0%, atomic percent, hereafter in at.%, referred to as TNMx B) were prepared. Macro/microstructure evolution, mechanical properties and deformation mechanisms of the alloys were studied systematically. Results showed that the microstructure of TNM-0.4 B and TNM-0.8 B alloy remained columnar dendrites, and the secondary dendritic arms of columnar grains were more obvious. When the content of B is 1.2%, the columnar dendrites transformed to equiaxed grains, and theα2/γ lamellae colony size was further refined in TNM-1.6 B and TNM-2.0 B alloy. The morphologies and kinds of the borides were changed with increasing B content, XRD results showed that Ti B phase appeared with 1.6%B content, and both Ti B and Ti B2 phase formed in TNM-2.0 B alloy. There were straight and curved Ti B phases located around grain boundaries in TNM-0.4 B and TNM-0.8 B alloy, and when the content of B increased to 1.2%, the curved Ti B phases were reduced, while the tiny and straight Ti B phases increased. With further increasing B content to 1.6% and 2.0%, the tiny and straight Ti B phases were coarser. Compressive testing results showed that the mechanical properties of the TNM alloy were enhanced with increasing B content. The maximum strength and strain of TNM alloy were 2339 MPa and33.7% with 1.6% B addition. The compressive strength and strain were mainly enhanced via refinement of lamellar colony and formation of Ti B, and it is found that pile-up of dislocations and deformed twins promoted by Ti B are predominant in improving the mechanical properties of TNM alloys with higher strength and strain. | Yingmei Tan Ruirun Chen Hongze Fang Yangli Liu Hongzhi Cui Yanqing Su Jingjie Guo Hengzhi Fu | 2022 | Journal of Materials Science & Technology2022，，7： | 2 |
| 13 | Rolling reduction-dependent deformation mechanisms and tensile properties in aβtitanium alloy显示文摘This work investigated the dependence of deformation mechanisms and mechanical properties on cold rolling reductions of the metastable TB8 titanium alloy.Results shown that the crystal orientation of the matrix changes with the increasing level of reduction,leading to the activation of complex deformation mechanisms in the matrix.When the rolling reduction is 10%,the deformation mechanisms are dominated by dislocations and{332}<113>deformation twins.As the reductions increase to 20%-50%,the secondary deformation twinning(SDT)is triggered in primary deformation twins besides the primary kink band is activated.Meanwhile,the secondary kink bands and{332}<113>twins have be observed in the primary kink bands.When the reduction reaches to 60%,the deformation mechanisms are dominated by dislocations and deformation twins.Furthermore,the matrix refined by crisscrossing among the twins,kink bands and other deformation mechanisms during cold rolling,which shortens the dislocation mean free path and then affects the strength and shape of the alloy.The dynamic Hall-Petch effect and the interaction between multi-scale deformed structures control the work hardening behavior of the alloy. | Zhaoxin Du Qiwei He Ruirun Chen Fei Liu Jingyong Zhang Fei Yang Xueping Zhao Xiaoming Cui Jun Cheng | 2022 | Journal of Materials Science & Technology2022，，9： | 2 |
| 14 | Directional solidification of titanium alloys by electromagnetic confinement in cold crucible 显示文摘 | DING Hongsheng CHEN Ruirun GUO Jingjie | 2005 | Materials Letters2005，59，7： | 1 |
| 15 | Optimizing the microstructures and mechanical properties of Al-Cu-based alloys with large solidification intervals by coupling travelling magnetic fields with sequential solidification显示文摘Alloys with large solidification intervals are prone to issues from the disordered growth and defect formation;accordingly, finding ways to effectively optimize the microstructure, further to improve the mechanical properties is of great importance. To this end, we couple travelling magnetic fields with sequential solidification to continuously regulate the mushy zones of Al-Cu-based alloys with large solidification intervals. Moreover, we combine experiments with simulations to comprehensively analyze the mechanisms on the optimization of microstructure and properties. Our results indicate that only downward travelling magnetic fields coupled with sequential solidification can obtain the refined and uniform microstructure, and promote the growth of matrix phase -Al along the direction of temperature gradient.Additionally, the secondary dendrites and precipitates are reduced, while the solute partition coefficient and solute solid-solubility are raised. Ultimately, downward travelling magnetic fields can increase the ultimate tensile strength, yield strength, elongation and hardness from 196.2 MPa, 101.2 MPa, 14.5 % and85.1 kg mm-2 without travelling magnetic fields to 224.1 MPa, 114.5 MPa, 17.1 % and 102.1 kg mm-2,and improve the ductility of alloys. However, upward travelling magnetic fields have the adverse effects on microstructural evolution, and lead to a reduction in the performance and ductility. Our findings demonstrate that long-range directional circular flows generated by travelling magnetic fields directionally alter the transformation and redistribution of solutes and temperature, which finally influences the solidification behavior and performance. Overall, our research present not only an innovative method to optimize the microstructures and mechanical properties for alloys with large solidification intervals,but also a detailed mechanism of travelling magnetic fields on this optimization during the sequential solidification. | Lei Luo Liangshun Luo Robert O.Ritchie Yanqing Su Binbin Wang Liang Wang Ruirun Chen Jingjie Guo Hengzhi Fu | 2021 | Journal of Materials Science & Technology2021，，2： | 1 |
| 16 | Continuous melting and directional solidification of silicon ingot with an electromagnetic cold crucible显示文摘In order to avoid contamination from the crucible and to modify the structures,a new solidification method based on cold crucible technology was used to prepare silicon ingots.A silicon ingot with square cross section was directionally solidified with a cold crucible.The mechanism of the cold crucible directional solidification of silicon ingot was revealed.Due to the induction heat that was released in the surface layer and the incomplete contact between the crucible and the melt,the lateral heat loss was reduced and the silicon ingot was directionally solidified.The structures,dislocation defects and the grain growth orientation of the ingot were determined.The results show that neither intergranular nor intragranular precipitates are found in the ingot,except for the top part that was the last to solidify.The average dislocation density is about 1 to 2×106 cm-2.The grains are preferentially <220> orientated. | Huang Feng Chen Ruirun Guo Jingjie Ding Hongsheng Su Yanqing Yang Jieren Fu Hengzhi | 2012 | China Foundry2012，9，1： | 1 |
| 17 | Progress in research on cold crucible directional solidification of titanium based alloys显示文摘Cold crucible directional solidification(CCDS)is a newly developed technique,which combines the advantages of the cold crucible and continuous melting.It can be applied to directionally solidify reactive,high purity and refractory materials.This paper describes the principle of CCDS and its characteristics;development of the measurement and numerical calculation of the magnetic field,flow field and temperature field in CCDS;and the CCDS of Ti based alloys.The paper also reviews original data obtained by some scholars,including the present authors,reported in separate publications in recent years.In Ti based alloys,Ti6Al4V,TiAl alloys and high Nb-containing TiAl alloys,have been directionally solidified in different cold crucibles.The crosssections of the cold crucibles include round,near rectangular and square with different sizes.Tensile testing results show that the elongation of directionally solidified Ti6Al4V can be improved to 12.7%from as cast5.4%.The strength and the elongation of the directionally solidified Ti47Al2Cr2Nb and Ti44Al6Nb1.0Cr2.0V are 650 MPa/3%and 602.5MPa/1.20%,respectively.The ingots after CCDS can be used to prepare turbine or engine blades,and are candidates to replace Ni super-alloy at temperatures of 700 to 900°C. | Chen Ruirun Guo Jingjie Chen Xiaoyu Dong Shulin Ding Hongsheng Su Yanqing Fu Hengzhi | 2014 | China Foundry2014，11，4： | 1 |
| 18 | Effects of Tantalum on Microstructure Evolution and Mechanical Properties of High-Nb TiAl Alloys Reinforced by Ti2AlC显示文摘Experiments have been carried out to study the relationship between the addition of tantalum and microstructure,especially the formation of the B2 phase in lamellar colonies.The mechanical properties,with different contents of Ta,were also measured.Ti46Al8Nb2.6CxTa alloys were prepared by casting with the content of Ta varying from zero to 1.0 at.%.Experimental results show that the B2 phase forms in lamellar colonies with the addition of Ta,and its content increases when the content of Ta increases.Meanwhile,theγphase decreases and the lattice parameter of theα2 phase increases.The size of the lamellar colony decreased from 29.9 to 21.6μm.Ta dissolves into Ti_(2)AlC by substitution,and its solubility is more than 1.1%tested by EDS.Nb,which is necessary for the formation of the B2 phase,comes from two aspects.The first is that Ta dissolves into the Ti_(2)AlC and partly replaces the Nb atom and the second is the decrease in theγphase because it has higher solid solubility for Nb.The increase in Nb in the liquid phase increases the composition supercooling and heteronucleation at the solidification front,which accounts for refining the lamellar colony.Room temperature compressive testing showed that the compressive strength and the strain increased when the Ta content increased up to 0.8%and then decreased.Improvement of the compressive properties resulted from the grain boundary strengthening and their decrease induced by more content of the B2 phase.Tensile properties,at elevated temperature,were improved with testing temperature increasing from 750 to 950℃,because solid solution strengthening is a major influence factor. | Hongze Fang Ruirun Chen Yong Yang Yanqing Su Hongsheng Ding Jingjie Guo | 2019 | Research2019，，1： | 1 |
| 19 | Feasibility of Directional Solidification of Silicon Ingot by Electromagnetic Casting显示文摘 | Huang Feng Chen Ruirun Guo Jingjie | 2012 | Materials Science in Semiconductor Processing2012，15，： | 1 |
| 20 | Using multiple regression analysis to predict directionally solidified TiAl mechanical property显示文摘The mechanical properties of TiAl alloy prepared by directional solidification were predicted through a machine learning algorithm model.The composition,input power,and pulling speed were designated as input variables as representative factors influencing mechanical properties,and multiple linear regression analysis was conducted by collecting data obtained from the literature.In this study,the R^(2)value of the tensile strength prediction result was 0.7159,elongation was 0.8459,nanoindentation hardness was 0.7573,and interlamellar spacing was 0.9674.As the R^(2)value of the elongation obtained through the analysis was higher than the R^(2)value of the tensile strength,it was confirmed that the elongation had a closer relationship with the input variables(composition,input power,pulling speed)than the tensile strength.By adding the elongation to the tensile strength as an input variable,it was observed that the R^(2)value was further increased.The tensile test prediction results were divided into four groups:The group with the lowest residual value(predicted value-actual value)was designated as group A,and the group with the largest residual value was designated as group D.When comparing the values of group A and group D,more overpredictions occurred in group A,while more under predictions occurred in group D.Using the residuals and R^(2)values,the cause of the well-prediction was studied,and through this,the relationship between the mechanical properties and the microstructure was quantitatively investigated. | Seungmi Kwak Jaehwang Kim Hongsheng Ding Xuesong Xu Ruirun Chen Jingjie Guo Hengzhi Fu | 2022 | Journal of Materials Science & Technology2022，，9： | 1 |
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