采用强流脉冲电子束对YW2硬质合金刀具进行辐照表面改性。根据Box-Behnken中心组合方法设计3因素3水平实验方案,以刀具表面的显微硬度和粗糙度为响应值,对加速电压、工作电流和脉冲次数等辐照工艺参数进行优化。实验结果表明,经综合分...采用强流脉冲电子束对YW2硬质合金刀具进行辐照表面改性。根据Box-Behnken中心组合方法设计3因素3水平实验方案,以刀具表面的显微硬度和粗糙度为响应值,对加速电压、工作电流和脉冲次数等辐照工艺参数进行优化。实验结果表明,经综合分析优化后的脉冲电子束辐照最优参数:加速电压10 k V,工作电流180 A,脉冲次数45次。与未经处理刀具相比,该工艺下辐照后的YW2硬质合金刀具的显微硬度明显提高,而粗糙度值降低;对TC4钛合金的切削实验结果也验证了优化工艺处理后刀具的切削性能明显得到提高。展开更多
This paper studies the structural evolution of （AgCo）201 clusters with different Co concentrations under various temperature conditions by using molecular dynamics with the embedded atom method. The most stable posi...This paper studies the structural evolution of （AgCo）201 clusters with different Co concentrations under various temperature conditions by using molecular dynamics with the embedded atom method. The most stable position for Co atoms in the cluster is the subsurface layer at low temperature （lower than 200 K for the Ag200Col cluster）. The position changes to the core layer with the increase of temperature, but there is an energy barrier in the middle layer. This makes the Ag-Co cluster form an Ag Co-Ag three-shell onion-like configuration. When the temperature is high enough [higher than 800 K for （AgCo）2m clusters with 50% Co], Co atoms can obtain enough energy to overcome the energy barrier and the cluster forms an Ag-Co core-shell configuration. Amorphization for the onion-like and core-shell clusters is induced by the large lattice misfit at Ag-Co interfaces. The structural evolution in the Ag-Co cluster is related to the release of excess energy.展开更多
We study the icosahedral transformations of solid Cu Co clusters with different initial configurations by using molecular dynamics with the embedded atom method. It is found that the formation of symmetric icosahedral...We study the icosahedral transformations of solid Cu Co clusters with different initial configurations by using molecular dynamics with the embedded atom method. It is found that the formation of symmetric icosahedral cluster is strongly related to the atomic number and initial configuration. The transformation originates from the surface into the interior of the cluster and is a structural change which is rapid and diffusionless. The icosahedral clusters with any composition and configuration, such as core-shell or three-shell duster, can be prepared by the means of solid-solid phase transition in bimetallic clusters.展开更多
采用不同能量密度的电子束对硬质合金刀具Ti Al N涂层进行轰击处理,研究了电子束能量密度对Ti Al N涂层表面改性后的微观组织和硬度的影响。利用扫描电镜(SEM)、能谱分析(EDS)、X射线衍射仪(XRD)分别对Ti Al N涂层进行表面形貌观察、元...采用不同能量密度的电子束对硬质合金刀具Ti Al N涂层进行轰击处理,研究了电子束能量密度对Ti Al N涂层表面改性后的微观组织和硬度的影响。利用扫描电镜(SEM)、能谱分析(EDS)、X射线衍射仪(XRD)分别对Ti Al N涂层进行表面形貌观察、元素分析和物相分析,并对涂层表面进行粗糙度和显微硬度测试。结果表明,随着能量密度的增加,涂层表面更趋于致密。在相同的能量密度1.75 J·cm^(-2)下,采用相对较低的阴极加速电压7 k V和较高电流强度130 A轰击时,涂层表面粗糙度最低达0.15μm。经电子束轰击后的Ti Al N相衍射峰相对强度有所提高;涂层相衍射峰不同程度地向高角度偏移,并且同样能量密度条件下加速电压越高,偏移角度越大;同时涂层相衍射峰有一定宽化趋势。表明电子束轰击后Ti Al N涂层产生较大的压应力和热应力,使晶粒细化,并且在一定的热应力驱动下有利于原子扩散,形成较宽的过渡层,从而提高涂层和基体间结合力。显微硬度随着能量密度的增加呈上升趋势,而相同的能量密度条件,加速电压的提高有助于涂层表面硬化。展开更多
文摘采用强流脉冲电子束对YW2硬质合金刀具进行辐照表面改性。根据Box-Behnken中心组合方法设计3因素3水平实验方案,以刀具表面的显微硬度和粗糙度为响应值,对加速电压、工作电流和脉冲次数等辐照工艺参数进行优化。实验结果表明,经综合分析优化后的脉冲电子束辐照最优参数:加速电压10 k V,工作电流180 A,脉冲次数45次。与未经处理刀具相比,该工艺下辐照后的YW2硬质合金刀具的显微硬度明显提高,而粗糙度值降低;对TC4钛合金的切削实验结果也验证了优化工艺处理后刀具的切削性能明显得到提高。
基金supported by the National Natural Science Foundation of China(Grant No 50374027)the program for New Century Excellent Talents in University(Grant No NCET-06-0289)the 111 project of China(Grant No B07015)
文摘This paper studies the structural evolution of （AgCo）201 clusters with different Co concentrations under various temperature conditions by using molecular dynamics with the embedded atom method. The most stable position for Co atoms in the cluster is the subsurface layer at low temperature （lower than 200 K for the Ag200Col cluster）. The position changes to the core layer with the increase of temperature, but there is an energy barrier in the middle layer. This makes the Ag-Co cluster form an Ag Co-Ag three-shell onion-like configuration. When the temperature is high enough [higher than 800 K for （AgCo）2m clusters with 50% Co], Co atoms can obtain enough energy to overcome the energy barrier and the cluster forms an Ag-Co core-shell configuration. Amorphization for the onion-like and core-shell clusters is induced by the large lattice misfit at Ag-Co interfaces. The structural evolution in the Ag-Co cluster is related to the release of excess energy.
基金Supported by the National Natural Science Foundation of China under Grant No 50374027, the Programme for New Century Excellent Talents in University under Grant No NCET-06-0289, and the 111 Project of the Ministry of Education of China under Grant No B07015.
文摘We study the icosahedral transformations of solid Cu Co clusters with different initial configurations by using molecular dynamics with the embedded atom method. It is found that the formation of symmetric icosahedral cluster is strongly related to the atomic number and initial configuration. The transformation originates from the surface into the interior of the cluster and is a structural change which is rapid and diffusionless. The icosahedral clusters with any composition and configuration, such as core-shell or three-shell duster, can be prepared by the means of solid-solid phase transition in bimetallic clusters.
文摘采用不同能量密度的电子束对硬质合金刀具Ti Al N涂层进行轰击处理,研究了电子束能量密度对Ti Al N涂层表面改性后的微观组织和硬度的影响。利用扫描电镜(SEM)、能谱分析(EDS)、X射线衍射仪(XRD)分别对Ti Al N涂层进行表面形貌观察、元素分析和物相分析,并对涂层表面进行粗糙度和显微硬度测试。结果表明,随着能量密度的增加,涂层表面更趋于致密。在相同的能量密度1.75 J·cm^(-2)下,采用相对较低的阴极加速电压7 k V和较高电流强度130 A轰击时,涂层表面粗糙度最低达0.15μm。经电子束轰击后的Ti Al N相衍射峰相对强度有所提高;涂层相衍射峰不同程度地向高角度偏移,并且同样能量密度条件下加速电压越高,偏移角度越大;同时涂层相衍射峰有一定宽化趋势。表明电子束轰击后Ti Al N涂层产生较大的压应力和热应力,使晶粒细化,并且在一定的热应力驱动下有利于原子扩散,形成较宽的过渡层,从而提高涂层和基体间结合力。显微硬度随着能量密度的增加呈上升趋势,而相同的能量密度条件,加速电压的提高有助于涂层表面硬化。
