The microstructure of an explosively compacted Nd-Fe-B permanent magnet(Nd-Fe-B) was investigated by means of TEM and XRD. It is shown that there are three kinds of phases: Nd2Fe14B matrix phase, O-rich phases and N...The microstructure of an explosively compacted Nd-Fe-B permanent magnet(Nd-Fe-B) was investigated by means of TEM and XRD. It is shown that there are three kinds of phases: Nd2Fe14B matrix phase, O-rich phases and Nd-rich phase with different structures and compositions in the magnet. The hard magnetic phase Nd2Fe14B is tetragonal, which lattice parameters are determined to be a=0.88 nm and c=1.22 nm. The O-rich phase locates at the grain boundaries and the triple junctions has fcc structure whose lattice parameter is a=0.559 nm. A dislocation is observed in this phase. It is also found that a large number of the block-shaped Nd-rich phases with hcp structure are embedded in the Nd2Fe14B matrix or at grain boundary. Their lattice parameters are determined to be a=0.395 nm and c=0.628 nm.展开更多
CuCr bulk alloy was produced by mechanical alloying and explosive compaction technology. Four kinds of milling time were used to analyze the function and influence on mechanical alloying. The samples were characterize...CuCr bulk alloy was produced by mechanical alloying and explosive compaction technology. Four kinds of milling time were used to analyze the function and influence on mechanical alloying. The samples were characterized by X-ray diffraction and optical microscope, and the density and hardness of the four samples were detected. The results show that the CuCr grain size is decreased with the milling time increasing, and nano-crystalline is observed in both Cu and Cr phase after 20 h milling. The density and hardness of samples are also increased with the increase of the milling time, so that the sample relative density reaches 96.6% and hardness reaches HV 217. The results indicate that high quality of CuCr bulk alloy can be manufactured using explosive compaction method when mechanical alloying and explosive compaction process parameters are reasonably selected.展开更多
Anisotropic bonded magnets were prepared by warm compaction using anisotropic Nd-Fe-B powder. The forming process, magnetic properties, and temperature stability were studied. The results indicate that the optimal tem...Anisotropic bonded magnets were prepared by warm compaction using anisotropic Nd-Fe-B powder. The forming process, magnetic properties, and temperature stability were studied. The results indicate that the optimal temperature of the process, which was decided by the vis-cosity of the binders, was 110°C. With increasing pressure, the density of the magnets increased. When the pressure was above 700 MPa, the powder particles were destroyed and the magnetic properties decreased. The magnetic properties of the anisotropic bonded magnets were as follows: remanence Br=0.98 T, intrinsic coercivity iHc=1361 kA/m, and maximum energy product BHmax=166 kJ/m3. The magnets had excellent thermal stability because of the high coercivity and good squareness of demagnetization curves. The flux density of the magnets was 35% higher than that of isotropic bonded Nd-Fe-B magnets at 120°C for 1000 h. The flux density of the bonded magnets showed little change with regard to temperature.展开更多
Warm compaction and room temperature compaction were applied to prepare bonded Nd-Fe-B magnets. The results indicated that the density of magnet was determined by the compaction pressure and warm compaction temperatur...Warm compaction and room temperature compaction were applied to prepare bonded Nd-Fe-B magnets. The results indicated that the density of magnet was determined by the compaction pressure and warm compaction temperature, whereas, the thermosetting temperature could hardly affect the density of magnet. The mechanical properties of magnets were the best when the thermosetting temperature was 200 ℃. The Br, Hob, and (BH)max of warm compaction magnet were higher than those of room compaction. When the warm compaction temperature and thermosetting temperature were invariable, the density of magnet increased with the increase of compaction pressure, which resulted in the increase of Br, Hcb, and (BH)max of magnet and the decrease of Hcj of magnet. When the warm compaction temperature and compaction pressure were invariable, the magnetic properties of magnets decreased with the increase of thermosetting temperature. The magnetic properties of warm compaction molding magnets were better than those of injection molding magnets.展开更多
CuCr alloys are prepared by mechanical alloying and explosive compaction. After we have studied their structure and flaws, the results show that the CuCr alloys have definite strength and toughness, while their fractu...CuCr alloys are prepared by mechanical alloying and explosive compaction. After we have studied their structure and flaws, the results show that the CuCr alloys have definite strength and toughness, while their fractured surface displays ductile characteristics. In the metallurgical structure, CuCr alloys are composed of two phases of uniform distribution; the SEM morphology is like thin strips with an end arrangement that is bonded to each other and the two-phase distribution of CuCr alloys is more homogenous. It is in only in a very small zone that formation of Cu-rich and Cr-rich phases take place. The flaws of the compaction samples are mainly central-holes and cracks.展开更多
Ti1Al2O3 Functionally Gradient Material (FGM) was prepared by an explosive compaction/SHS process. Ten sheets of the compounding powder were laminated and pressed to get a green body of FGM. It was then compacted expl...Ti1Al2O3 Functionally Gradient Material (FGM) was prepared by an explosive compaction/SHS process. Ten sheets of the compounding powder were laminated and pressed to get a green body of FGM. It was then compacted explosively By burying the explosive compaction body into a stoichiometric Al/TiO2 mixture and igniting the combustion of the stoichiometric Al/TiO2 mixture, the SHS reaction of the explosive compaction body was initiated by the heat released from the combustion of the stoichiometric Al/TiO2 mixture. In this way, Ti/Al2O3 FGM was synthesized. The adiabatic temperatures of each gradient layer were calculated when the preheating temperatures were 298 K and 1173 K, respectively The microstructure, composition and properties of Ti/Al2O3 FGM and the reaction mechanism of each gradient layer were studied. It was found that Ti/Al2O3 FGM prepared by the explosive compaction/SHS process had a high density and a high microhardness. Its structure, composition and properties showed apparent gradient distribution. The structure of the standard stoichiometric ratio gradient layer of FGM was a network structure. Its reaction mode could be described as follows: Al powder melted first, then the molten Al penetrated into the TiO2 zone and reacted with TiO2, and big pores were left in the original positions of Al powder. The reaction of gradient layers with the addition of Al3O3 as diluents was similar to that of the standard stoichiometric ratio gradient layer, so were their structure and composition. However, the reaction of gradient layers with the addition of Ti as diluents was more complex and the composition deviated slightly from the designed one展开更多
Powder compaction is one of the most crucial processes in initiating explosive device manufacturing. The quality of powder compaction may influence the performances of product directly. Traditional powder compaction m...Powder compaction is one of the most crucial processes in initiating explosive device manufacturing. The quality of powder compaction may influence the performances of product directly. Traditional powder compaction mainly makes use of manual gravitational spiral loading machine or lever loading machine. Potential accident by the strike in powder compaction of initiating explosive device could risk life, property and the environment. To prevent this risk, automatic control system and control strategy can be used to guarantee no strike in pressing process. The scope of this paper is to analyze and review the control strategy for powder compact and discuss the experimental results for the application of the proposed strategy.展开更多
The production of CuCr alloys utilizing explosive compaction was studied. Mixture powders of CuCr alloys placed in tubes with a dimension of d14.0 mm×21.4 mm can be compacted using explosive pads of 16.5 mm or 22...The production of CuCr alloys utilizing explosive compaction was studied. Mixture powders of CuCr alloys placed in tubes with a dimension of d14.0 mm×21.4 mm can be compacted using explosive pads of 16.5 mm or 22.5 mm. Thicker pads of explosive make the compacts more porous. The effects of the ratio of m e/m p, ratio of m e/(m p+m t) and impact energy on the density of compacts were similar, they were chosen to control explosive compaction, respectively. When adequate value of the parameters m e/m p, m e/(m t+m p) and impact energy of unit area of tube was chosen, high density(7.858 g/cm 3), high hardness(HB189) and low conductance (13.6 MS/m) of CuCr alloys could be made by explosive compaction. The general properties of CuCr alloys by explosive compaction are similar to those of CuCr alloys by traditional process.展开更多
Observations of microstructure of explosive compacts made of Al or Al-Li alloy powders by atomization with water,nitrogen or ultrasoic Ar gas were carried out under optical and scanning electron microscopes.The rsults...Observations of microstructure of explosive compacts made of Al or Al-Li alloy powders by atomization with water,nitrogen or ultrasoic Ar gas were carried out under optical and scanning electron microscopes.The rsults indicate that super quality explosive compact can only be obtained by powders of which the thickness of the oxide layer is less than 30 nm.展开更多
Direct explosive compaction and sintering of a mixture of Ti-30Al-2Mn(wt%)and Ti-38Al-2Mn(wt%) intermetallic compound powders were carried out.Microstructure and phase characteristics of the alloys were analysed by TE...Direct explosive compaction and sintering of a mixture of Ti-30Al-2Mn(wt%)and Ti-38Al-2Mn(wt%) intermetallic compound powders were carried out.Microstructure and phase characteristics of the alloys were analysed by TEM,SEM,X-ray diffractometry and optical microscopy.The results showed that the rel- ative density of the samples which were explosive-compacted and sintered reached 99.90%,and fine grain structure was obtained.Through the explosive-compacting and then sintering at 1373 K in argon atmos- phere,mutual diffusion between Ti-30Al-2Mn particles and Ti-38Al-2Mn particles took place and TiAl phase was formed in the alloy.TiAl based alloys prepared by high-energy ball-milling powders had much fi- ner grain size than those prepared by general ball-milling powdeis.展开更多
为获得黏土中爆炸成坑体积与耦合地冲击能量的关系,采用10.5 g TNT厘米级球形炸药球作为爆炸源,在Φ1500 mm×1490 mm分层式爆炸装置中开展了变埋深条件下的爆炸实验,利用3D扫描设备记录不同埋深下弹坑的真实体积,并通过动态土压力...为获得黏土中爆炸成坑体积与耦合地冲击能量的关系,采用10.5 g TNT厘米级球形炸药球作为爆炸源,在Φ1500 mm×1490 mm分层式爆炸装置中开展了变埋深条件下的爆炸实验,利用3D扫描设备记录不同埋深下弹坑的真实体积,并通过动态土压力传感器测得地冲击传播衰减规律。实验结果表明:随埋深增大,耦合至黏土中的有效地冲击能量急剧增大,装药中心下方的有效弹坑体积与耦合至黏土中的有效地冲击能量基本呈正比关系,当装药比例埋深与封闭爆炸条件下爆炸空腔半径相当时,耦合至黏土中的有效地冲击能量基本达到饱和。结合实验结果给出了黏土中爆炸耦合地冲击能量分配随装药比例埋深的变化规律,建立了地下爆炸等效封闭当量计算方法,为地下工程抗爆设计提供了理论依据。展开更多
基金Project(50071035) supported by the National Natural Science Foundation of China Project(02ZE14054) supported bythe Natural Science Foundation of Shanghai China
文摘The microstructure of an explosively compacted Nd-Fe-B permanent magnet(Nd-Fe-B) was investigated by means of TEM and XRD. It is shown that there are three kinds of phases: Nd2Fe14B matrix phase, O-rich phases and Nd-rich phase with different structures and compositions in the magnet. The hard magnetic phase Nd2Fe14B is tetragonal, which lattice parameters are determined to be a=0.88 nm and c=1.22 nm. The O-rich phase locates at the grain boundaries and the triple junctions has fcc structure whose lattice parameter is a=0.559 nm. A dislocation is observed in this phase. It is also found that a large number of the block-shaped Nd-rich phases with hcp structure are embedded in the Nd2Fe14B matrix or at grain boundary. Their lattice parameters are determined to be a=0.395 nm and c=0.628 nm.
基金Project(10802038) supported by the National Natural Science Foundation of ChinaProject(0802019C) supported by Jiangsu Planned Projects for Postdoctoral Research Funds
文摘CuCr bulk alloy was produced by mechanical alloying and explosive compaction technology. Four kinds of milling time were used to analyze the function and influence on mechanical alloying. The samples were characterized by X-ray diffraction and optical microscope, and the density and hardness of the four samples were detected. The results show that the CuCr grain size is decreased with the milling time increasing, and nano-crystalline is observed in both Cu and Cr phase after 20 h milling. The density and hardness of samples are also increased with the increase of the milling time, so that the sample relative density reaches 96.6% and hardness reaches HV 217. The results indicate that high quality of CuCr bulk alloy can be manufactured using explosive compaction method when mechanical alloying and explosive compaction process parameters are reasonably selected.
文摘Anisotropic bonded magnets were prepared by warm compaction using anisotropic Nd-Fe-B powder. The forming process, magnetic properties, and temperature stability were studied. The results indicate that the optimal temperature of the process, which was decided by the vis-cosity of the binders, was 110°C. With increasing pressure, the density of the magnets increased. When the pressure was above 700 MPa, the powder particles were destroyed and the magnetic properties decreased. The magnetic properties of the anisotropic bonded magnets were as follows: remanence Br=0.98 T, intrinsic coercivity iHc=1361 kA/m, and maximum energy product BHmax=166 kJ/m3. The magnets had excellent thermal stability because of the high coercivity and good squareness of demagnetization curves. The flux density of the magnets was 35% higher than that of isotropic bonded Nd-Fe-B magnets at 120°C for 1000 h. The flux density of the bonded magnets showed little change with regard to temperature.
基金supported by the National Natural Science Foundation of China (Grant No.50074014)
文摘Warm compaction and room temperature compaction were applied to prepare bonded Nd-Fe-B magnets. The results indicated that the density of magnet was determined by the compaction pressure and warm compaction temperature, whereas, the thermosetting temperature could hardly affect the density of magnet. The mechanical properties of magnets were the best when the thermosetting temperature was 200 ℃. The Br, Hob, and (BH)max of warm compaction magnet were higher than those of room compaction. When the warm compaction temperature and thermosetting temperature were invariable, the density of magnet increased with the increase of compaction pressure, which resulted in the increase of Br, Hcb, and (BH)max of magnet and the decrease of Hcj of magnet. When the warm compaction temperature and compaction pressure were invariable, the magnetic properties of magnets decreased with the increase of thermosetting temperature. The magnetic properties of warm compaction molding magnets were better than those of injection molding magnets.
文摘CuCr alloys are prepared by mechanical alloying and explosive compaction. After we have studied their structure and flaws, the results show that the CuCr alloys have definite strength and toughness, while their fractured surface displays ductile characteristics. In the metallurgical structure, CuCr alloys are composed of two phases of uniform distribution; the SEM morphology is like thin strips with an end arrangement that is bonded to each other and the two-phase distribution of CuCr alloys is more homogenous. It is in only in a very small zone that formation of Cu-rich and Cr-rich phases take place. The flaws of the compaction samples are mainly central-holes and cracks.
文摘Ti1Al2O3 Functionally Gradient Material (FGM) was prepared by an explosive compaction/SHS process. Ten sheets of the compounding powder were laminated and pressed to get a green body of FGM. It was then compacted explosively By burying the explosive compaction body into a stoichiometric Al/TiO2 mixture and igniting the combustion of the stoichiometric Al/TiO2 mixture, the SHS reaction of the explosive compaction body was initiated by the heat released from the combustion of the stoichiometric Al/TiO2 mixture. In this way, Ti/Al2O3 FGM was synthesized. The adiabatic temperatures of each gradient layer were calculated when the preheating temperatures were 298 K and 1173 K, respectively The microstructure, composition and properties of Ti/Al2O3 FGM and the reaction mechanism of each gradient layer were studied. It was found that Ti/Al2O3 FGM prepared by the explosive compaction/SHS process had a high density and a high microhardness. Its structure, composition and properties showed apparent gradient distribution. The structure of the standard stoichiometric ratio gradient layer of FGM was a network structure. Its reaction mode could be described as follows: Al powder melted first, then the molten Al penetrated into the TiO2 zone and reacted with TiO2, and big pores were left in the original positions of Al powder. The reaction of gradient layers with the addition of Al3O3 as diluents was similar to that of the standard stoichiometric ratio gradient layer, so were their structure and composition. However, the reaction of gradient layers with the addition of Ti as diluents was more complex and the composition deviated slightly from the designed one
文摘Powder compaction is one of the most crucial processes in initiating explosive device manufacturing. The quality of powder compaction may influence the performances of product directly. Traditional powder compaction mainly makes use of manual gravitational spiral loading machine or lever loading machine. Potential accident by the strike in powder compaction of initiating explosive device could risk life, property and the environment. To prevent this risk, automatic control system and control strategy can be used to guarantee no strike in pressing process. The scope of this paper is to analyze and review the control strategy for powder compact and discuss the experimental results for the application of the proposed strategy.
文摘The production of CuCr alloys utilizing explosive compaction was studied. Mixture powders of CuCr alloys placed in tubes with a dimension of d14.0 mm×21.4 mm can be compacted using explosive pads of 16.5 mm or 22.5 mm. Thicker pads of explosive make the compacts more porous. The effects of the ratio of m e/m p, ratio of m e/(m p+m t) and impact energy on the density of compacts were similar, they were chosen to control explosive compaction, respectively. When adequate value of the parameters m e/m p, m e/(m t+m p) and impact energy of unit area of tube was chosen, high density(7.858 g/cm 3), high hardness(HB189) and low conductance (13.6 MS/m) of CuCr alloys could be made by explosive compaction. The general properties of CuCr alloys by explosive compaction are similar to those of CuCr alloys by traditional process.
文摘Observations of microstructure of explosive compacts made of Al or Al-Li alloy powders by atomization with water,nitrogen or ultrasoic Ar gas were carried out under optical and scanning electron microscopes.The rsults indicate that super quality explosive compact can only be obtained by powders of which the thickness of the oxide layer is less than 30 nm.
基金Project was supported by National Advanced Materials Committee of China.
文摘Direct explosive compaction and sintering of a mixture of Ti-30Al-2Mn(wt%)and Ti-38Al-2Mn(wt%) intermetallic compound powders were carried out.Microstructure and phase characteristics of the alloys were analysed by TEM,SEM,X-ray diffractometry and optical microscopy.The results showed that the rel- ative density of the samples which were explosive-compacted and sintered reached 99.90%,and fine grain structure was obtained.Through the explosive-compacting and then sintering at 1373 K in argon atmos- phere,mutual diffusion between Ti-30Al-2Mn particles and Ti-38Al-2Mn particles took place and TiAl phase was formed in the alloy.TiAl based alloys prepared by high-energy ball-milling powders had much fi- ner grain size than those prepared by general ball-milling powdeis.
文摘为获得黏土中爆炸成坑体积与耦合地冲击能量的关系,采用10.5 g TNT厘米级球形炸药球作为爆炸源,在Φ1500 mm×1490 mm分层式爆炸装置中开展了变埋深条件下的爆炸实验,利用3D扫描设备记录不同埋深下弹坑的真实体积,并通过动态土压力传感器测得地冲击传播衰减规律。实验结果表明:随埋深增大,耦合至黏土中的有效地冲击能量急剧增大,装药中心下方的有效弹坑体积与耦合至黏土中的有效地冲击能量基本呈正比关系,当装药比例埋深与封闭爆炸条件下爆炸空腔半径相当时,耦合至黏土中的有效地冲击能量基本达到饱和。结合实验结果给出了黏土中爆炸耦合地冲击能量分配随装药比例埋深的变化规律,建立了地下爆炸等效封闭当量计算方法,为地下工程抗爆设计提供了理论依据。