The influence of in-situ synthesized TiC nanoparticles on age-hardening behavior of Al–Cu alloys was investigated in Al–4.5 Cu–1.5 TiC alloy. It was found that TiC nanoparticles decrease the peak-age time effective...The influence of in-situ synthesized TiC nanoparticles on age-hardening behavior of Al–Cu alloys was investigated in Al–4.5 Cu–1.5 TiC alloy. It was found that TiC nanoparticles decrease the peak-age time effectively, from about 20 h for Al–4.5 Cu alloy decreasing to about 12 h for the Al–4.5 Cu–1.5 TiC. Mechanical property test shows that the age-hardening effect has been improved by the TiC nanoparticles. The increment of yield strength before and after aging is about 84 MPa for Al–4.5 Cu, while, it reaches to about113 MPa for the Al–4.5 Cu–1.5 TiC. After aging heat treatment, precipitates have been observed both in matrix and around TiC nanoparticles. Due to the difference of coefficient of thermal expansion between TiC and Al, high density dislocations in the Al–4.5 Cu–1.5 TiC were generated during water quenching after solution. Dislocations play a role of diffusion path for Cu atoms during aging, which reduces the peak-age time. Alpha-Al lattice distortion resulted from lattice mismatch of TiC/Al interface induces the precipitation of θ' phase around TiC nanoparticles, which increases the number density of θ' and improves the age-hardening effect. This finding is supposed to be also applicable to alloy systems of Al–Cu–Mg,Al–Cu–Mg–Li, Al–Cu–Mg–Ag, etc.展开更多
A kind of Al-TiB2/TiC in situ composite with a homogenous microstructure was successfully prepared through in situ reaction of pure Ti and Al-B-C alloy with molten aluminum.In order to improve the distribution of the ...A kind of Al-TiB2/TiC in situ composite with a homogenous microstructure was successfully prepared through in situ reaction of pure Ti and Al-B-C alloy with molten aluminum.In order to improve the distribution of the particles and mechanical properties of the composites,subsequent hot rolling with increasing reduction was carried out.The microstructure evolution of the composites was characterized using field emission scanning electron microscopy(FESEM)and the mechanical properties were studied through tensile tests and microhardness measurement.It is found that both the microstructure uniformity and mechanical properties of the composites are significantly improved with increasing rolling reduction.The ultimate tensile strength and microhardness of the composites with90%rolling reduction reach185.9MPa and HV59.8,respectively,140%and35%higher than those of as-cast ones.Furthermore,the strengthening mechanism of the composite was analyzed based on the fracture morphologies.展开更多
A new technology-rotationally accelerated shot peening（RASP）, was developed to prepare gradient structured materials. By using centrifugal acceleration principle and large steel balls, the RASP technology can produc...A new technology-rotationally accelerated shot peening（RASP）, was developed to prepare gradient structured materials. By using centrifugal acceleration principle and large steel balls, the RASP technology can produce much higher impact energy compared to conventional shot peening. As a proof-of-concept demonstration, the RASP was utilized to refine the surface layer in pure copper（Cu） with an average grain size of 85 nm. The grain size increases largely from surface downwards the bulk, forming an800 ？m thick gradient-structured surface layer and consequently a micro-hardness gradient. The difference between the RASP technology and other established techniques in preparing gradient structured materials is discussed. The RASP technology exhibits a promoting future for large-scale manufacturing of gradient materials.展开更多
Ultra-strong joints of pure Cu and Cu–30Zn alloy were obtained by friction stir welding under flowing water. The effects of heat inputting condition and material characteristics on the morphologies, microstructures a...Ultra-strong joints of pure Cu and Cu–30Zn alloy were obtained by friction stir welding under flowing water. The effects of heat inputting condition and material characteristics on the morphologies, microstructures and mechanical properties of welding joints were studied. Defect-free stirring zones of pure Cu and Cu–30Zn were characterized by onion-ringed structure and plastic flowing bands, respectively. Both low stacking fault energy and fast cooling condition contributed to the formation of small recrystallized grains less than 1 μm in stirring zones. The welding joints in both materials exhibited enhanced mechanical performances due to ultrafine-grained microstructure in stirring zones and disappearance of soft heataffected-zone. The technique of digital image correlation was used to study the tensile deformation behaviors of welding joints and verify the improved tensile properties.展开更多
TiC_x contained Al-Ti-C is a kind of grain refiner for Al alloys. In this work, the influence of C/Ti stoichiometry, i.e. the x value in TiC_x on grain refinement efficiency was investigated. TiC_x particles have been...TiC_x contained Al-Ti-C is a kind of grain refiner for Al alloys. In this work, the influence of C/Ti stoichiometry, i.e. the x value in TiC_x on grain refinement efficiency was investigated. TiC_x particles have been obtained in five Al-5Ti-m C（m = 0.1, 0.5, 0.8, 1, 1.25） master alloys and the x values were measured to be0.72, 0.75, 0.79, 0.81 and 0.8, respectively. It was found that the refinement performance of the master alloys had a close relationship with the x value of TiC_x . The Al-5Ti-m C alloy with lower-x TiC_x shows better refinement efficiency and anti-fading capability. It is supposed that TiC_x particles with lower x are more preferred to release Ti atoms during nucleating process and have a better Ti-absorbing capability.This contributes to the Ti-rich zone formation at TiC_x /melt interface, thus enhancing the refinement and anti-fading capability.展开更多
Density functional theory combined with the Gr¨uneisen approximation is used to calculate the thermal properties of single-walled boron nanotubes(BNTs).The specific heat and thermal expansion are investigated.The...Density functional theory combined with the Gr¨uneisen approximation is used to calculate the thermal properties of single-walled boron nanotubes(BNTs).The specific heat and thermal expansion are investigated.The thermal expansion coeffi-cient of the BNT is found to be significantly correlated with tube size and chirality.A remarkable thermal contraction is found at small tube diameters.These results indicate that BNTs would have potential applications in sensors,actuators,and memory materials.展开更多
Black phosphorus(BP)has garnered significant interest in the field of biomedicine because of its exceptional degradability.The oxidation product of BP phosphate has been utilized in numerous studies for the purpose of...Black phosphorus(BP)has garnered significant interest in the field of biomedicine because of its exceptional degradability.The oxidation product of BP phosphate has been utilized in numerous studies for the purpose of repairing bone defects and inducing apoptosis and autophagy in cancer cells.Nevertheless,this process has drawbacks in terms of low yield and a slow rate of phosphate production.In this study,we found that the oxidation rate of BP was increased 120-fold and the yield proportion of phosphate BP product was increased from 30%to 85%with the presence of less than 0.1%copper ions(Cu^(2+))in the reaction system.The enhancement was attributed to the fact that the presence of Cu^(2+)promoted the bonding of oxygen on the BP surface and then the desorption of phosphate molecules from the BP surface.This study offers a novel perspective on the process of BP oxidation and introduces innovative concepts for the development of biological drug delivery systems capable of rapid decomposition.展开更多
基金financially supported by the Key Program of the National Natural Science Foundation of China (No. 51731007)the National Natural Science Foundation of China (No. 51501092)
文摘The influence of in-situ synthesized TiC nanoparticles on age-hardening behavior of Al–Cu alloys was investigated in Al–4.5 Cu–1.5 TiC alloy. It was found that TiC nanoparticles decrease the peak-age time effectively, from about 20 h for Al–4.5 Cu alloy decreasing to about 12 h for the Al–4.5 Cu–1.5 TiC. Mechanical property test shows that the age-hardening effect has been improved by the TiC nanoparticles. The increment of yield strength before and after aging is about 84 MPa for Al–4.5 Cu, while, it reaches to about113 MPa for the Al–4.5 Cu–1.5 TiC. After aging heat treatment, precipitates have been observed both in matrix and around TiC nanoparticles. Due to the difference of coefficient of thermal expansion between TiC and Al, high density dislocations in the Al–4.5 Cu–1.5 TiC were generated during water quenching after solution. Dislocations play a role of diffusion path for Cu atoms during aging, which reduces the peak-age time. Alpha-Al lattice distortion resulted from lattice mismatch of TiC/Al interface induces the precipitation of θ' phase around TiC nanoparticles, which increases the number density of θ' and improves the age-hardening effect. This finding is supposed to be also applicable to alloy systems of Al–Cu–Mg,Al–Cu–Mg–Li, Al–Cu–Mg–Ag, etc.
基金Project(51501092)supported by the National Natural Science Foundation of ChinaProject(30915011332)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2014M550292)supported by China Postdoctoral Science Foundation
文摘A kind of Al-TiB2/TiC in situ composite with a homogenous microstructure was successfully prepared through in situ reaction of pure Ti and Al-B-C alloy with molten aluminum.In order to improve the distribution of the particles and mechanical properties of the composites,subsequent hot rolling with increasing reduction was carried out.The microstructure evolution of the composites was characterized using field emission scanning electron microscopy(FESEM)and the mechanical properties were studied through tensile tests and microhardness measurement.It is found that both the microstructure uniformity and mechanical properties of the composites are significantly improved with increasing rolling reduction.The ultimate tensile strength and microhardness of the composites with90%rolling reduction reach185.9MPa and HV59.8,respectively,140%and35%higher than those of as-cast ones.Furthermore,the strengthening mechanism of the composite was analyzed based on the fracture morphologies.
基金supports from the National Natural Science Foundation of China (Grant No. 51301092)Pangu Foundation are acknowledged
文摘A new technology-rotationally accelerated shot peening（RASP）, was developed to prepare gradient structured materials. By using centrifugal acceleration principle and large steel balls, the RASP technology can produce much higher impact energy compared to conventional shot peening. As a proof-of-concept demonstration, the RASP was utilized to refine the surface layer in pure copper（Cu） with an average grain size of 85 nm. The grain size increases largely from surface downwards the bulk, forming an800 ？m thick gradient-structured surface layer and consequently a micro-hardness gradient. The difference between the RASP technology and other established techniques in preparing gradient structured materials is discussed. The RASP technology exhibits a promoting future for large-scale manufacturing of gradient materials.
基金supported financially by the National Natural Science Foundation of China (Nos. 11672195 and 51301092)Sichuan Youth Science and Technology Foundation (No. 2016JQ0047)
文摘Ultra-strong joints of pure Cu and Cu–30Zn alloy were obtained by friction stir welding under flowing water. The effects of heat inputting condition and material characteristics on the morphologies, microstructures and mechanical properties of welding joints were studied. Defect-free stirring zones of pure Cu and Cu–30Zn were characterized by onion-ringed structure and plastic flowing bands, respectively. Both low stacking fault energy and fast cooling condition contributed to the formation of small recrystallized grains less than 1 μm in stirring zones. The welding joints in both materials exhibited enhanced mechanical performances due to ultrafine-grained microstructure in stirring zones and disappearance of soft heataffected-zone. The technique of digital image correlation was used to study the tensile deformation behaviors of welding joints and verify the improved tensile properties.
基金supported by a grant from the National Natural Science Fund of China (No. 51501092)the National Basic Research Program of China (No. 2012CB825702)
文摘TiC_x contained Al-Ti-C is a kind of grain refiner for Al alloys. In this work, the influence of C/Ti stoichiometry, i.e. the x value in TiC_x on grain refinement efficiency was investigated. TiC_x particles have been obtained in five Al-5Ti-m C（m = 0.1, 0.5, 0.8, 1, 1.25） master alloys and the x values were measured to be0.72, 0.75, 0.79, 0.81 and 0.8, respectively. It was found that the refinement performance of the master alloys had a close relationship with the x value of TiC_x . The Al-5Ti-m C alloy with lower-x TiC_x shows better refinement efficiency and anti-fading capability. It is supposed that TiC_x particles with lower x are more preferred to release Ti atoms during nucleating process and have a better Ti-absorbing capability.This contributes to the Ti-rich zone formation at TiC_x /melt interface, thus enhancing the refinement and anti-fading capability.
基金the National Basic Research Program of China(973 Program Grant No.2012CB215405)the National Natural Science Foundation of China(Grant No.11374272)City University of Hong Kong(Project No.7008092).
文摘Density functional theory combined with the Gr¨uneisen approximation is used to calculate the thermal properties of single-walled boron nanotubes(BNTs).The specific heat and thermal expansion are investigated.The thermal expansion coeffi-cient of the BNT is found to be significantly correlated with tube size and chirality.A remarkable thermal contraction is found at small tube diameters.These results indicate that BNTs would have potential applications in sensors,actuators,and memory materials.
基金supported by the National Natural Science Foundation of China(22125602,U2067215,22206087 and22076078)the National Key R&D Program of China(2022YFC3701402)
文摘Black phosphorus(BP)has garnered significant interest in the field of biomedicine because of its exceptional degradability.The oxidation product of BP phosphate has been utilized in numerous studies for the purpose of repairing bone defects and inducing apoptosis and autophagy in cancer cells.Nevertheless,this process has drawbacks in terms of low yield and a slow rate of phosphate production.In this study,we found that the oxidation rate of BP was increased 120-fold and the yield proportion of phosphate BP product was increased from 30%to 85%with the presence of less than 0.1%copper ions(Cu^(2+))in the reaction system.The enhancement was attributed to the fact that the presence of Cu^(2+)promoted the bonding of oxygen on the BP surface and then the desorption of phosphate molecules from the BP surface.This study offers a novel perspective on the process of BP oxidation and introduces innovative concepts for the development of biological drug delivery systems capable of rapid decomposition.
