W-containing refractory high-entropy alloys(RHEAs)are promising for elevated-temperature applications,while the complexity of dendritic microstructure poses challenges in achieving controllable machining performance.I...W-containing refractory high-entropy alloys(RHEAs)are promising for elevated-temperature applications,while the complexity of dendritic microstructure poses challenges in achieving controllable machining performance.In this work,the controllability of sinking electrical discharge machining(EDM)performance on dendritic-structured(TiVCr)_(95)W_(5)and(FeVCr)_(95)W_(5)RHEAs was evaluated using a mathematical model that expresses the relationship between discharge parameters and machining performance.A superior controllability of the material removal rate and surface roughness(Ra)was obtained by the high accuracy and good predictability of the model,with the R^(2)value close to 1 and a predicted error for Ra below 5%.This was attributed to the stable removal behavior of the dendritic microstructure.Melting was the primary removal mechanism for both dendrites and inter-dendrites.The W element can stabilize the removal behavior of constituent elements.No obvious compositional variation was observed within the crater formed in dendrites.As more W diffused into inter-dendrites,the variation of Cr and V in inter-dendrites reduced from approximately 20.0%to less than 2.0%.Similar melting removal mechanisms led to an analogous relationship between the machining performance and processing conditions of the two RHEAs.Compared to the relatively high surface roughness achieved by wire-EDM,the optimized Ra values of 0.329 and 0.728μm for(TiVCr)_(95)W_(5)and(FeVCr)_(95)W_(5),respectively,demonstrated the superiority of sinking EDM for RHEAs.The present findings have confirmed the superior controllable sinking EDM performance for W-containing RHEAs,providing useful guidance for the processing of W-containing RHEAs in practical applications.展开更多
In this paper,W-containing SiC-based ceramic nanocomposites were successfully prepared by a polymer-derived ceramic approach using allylhydridopolycarbosilane(AHPCS)as a SiC source,WC16 as a tungsten source,polystyren...In this paper,W-containing SiC-based ceramic nanocomposites were successfully prepared by a polymer-derived ceramic approach using allylhydridopolycarbosilane(AHPCS)as a SiC source,WC16 as a tungsten source,polystyrene(PS)as a pore forming agent as well as divinyl benzene(DVB)as a carbon rich source.High-temperature phase behavior of the W-containing SiC-based ceramics after heat treatment was studied,showing that excessive DVB content in the feed will inhibit the crystallinity of W-containing nanoparticles in the final ceramic nanocomposites.The high specific surface area(SSA)of 169.4-276.9 m^(2)/g can be maintained even at high temperature in the range of 1400-1500℃,due to the carbothermal reaction which usually occurs between 1300 and 1400℃.All prepared W-containing SiC-based nanocomposites reveal electrocatalytic activity for the hydrogen evolution reaction(HER).In detail,compared with reversible hydrogen electrode(RHE),the ceramic sample PWA-2-1300 after heat treatment at 1300℃ has the smallest overpotential of 286 mV when the current density is 10 mA·cm^(-2) in acid medium,indicating the promising perspective in the water splitting field.展开更多
基金supported by Anhui Provincial Natural Science Foundation(No.2308085ME172,2308085QE164)the National Magnetic Confinement Fusion Energy Research&Development(MCF Energy R&D)Program(No.2022YFE03140000)。
文摘W-containing refractory high-entropy alloys(RHEAs)are promising for elevated-temperature applications,while the complexity of dendritic microstructure poses challenges in achieving controllable machining performance.In this work,the controllability of sinking electrical discharge machining(EDM)performance on dendritic-structured(TiVCr)_(95)W_(5)and(FeVCr)_(95)W_(5)RHEAs was evaluated using a mathematical model that expresses the relationship between discharge parameters and machining performance.A superior controllability of the material removal rate and surface roughness(Ra)was obtained by the high accuracy and good predictability of the model,with the R^(2)value close to 1 and a predicted error for Ra below 5%.This was attributed to the stable removal behavior of the dendritic microstructure.Melting was the primary removal mechanism for both dendrites and inter-dendrites.The W element can stabilize the removal behavior of constituent elements.No obvious compositional variation was observed within the crater formed in dendrites.As more W diffused into inter-dendrites,the variation of Cr and V in inter-dendrites reduced from approximately 20.0%to less than 2.0%.Similar melting removal mechanisms led to an analogous relationship between the machining performance and processing conditions of the two RHEAs.Compared to the relatively high surface roughness achieved by wire-EDM,the optimized Ra values of 0.329 and 0.728μm for(TiVCr)_(95)W_(5)and(FeVCr)_(95)W_(5),respectively,demonstrated the superiority of sinking EDM for RHEAs.The present findings have confirmed the superior controllable sinking EDM performance for W-containing RHEAs,providing useful guidance for the processing of W-containing RHEAs in practical applications.
基金the National Natural Science Foundation of China(Nos.51872246 and 52061135102)for financial support.
文摘In this paper,W-containing SiC-based ceramic nanocomposites were successfully prepared by a polymer-derived ceramic approach using allylhydridopolycarbosilane(AHPCS)as a SiC source,WC16 as a tungsten source,polystyrene(PS)as a pore forming agent as well as divinyl benzene(DVB)as a carbon rich source.High-temperature phase behavior of the W-containing SiC-based ceramics after heat treatment was studied,showing that excessive DVB content in the feed will inhibit the crystallinity of W-containing nanoparticles in the final ceramic nanocomposites.The high specific surface area(SSA)of 169.4-276.9 m^(2)/g can be maintained even at high temperature in the range of 1400-1500℃,due to the carbothermal reaction which usually occurs between 1300 and 1400℃.All prepared W-containing SiC-based nanocomposites reveal electrocatalytic activity for the hydrogen evolution reaction(HER).In detail,compared with reversible hydrogen electrode(RHE),the ceramic sample PWA-2-1300 after heat treatment at 1300℃ has the smallest overpotential of 286 mV when the current density is 10 mA·cm^(-2) in acid medium,indicating the promising perspective in the water splitting field.
