中文摘要：

研究了Cr粉在机械球磨过程中粒度分布、晶粒尺寸和显微应变随球磨时间的变化规律.探讨了机械球磨过程中Cr粉的形貌特点及其细化机理.结果表明：Cr的细化主要发生在球磨前期（5h）,5h后细化速率明显减缓,球磨25h时,Cr粉的表面积平均粒径（1.383μm）和体积平均粒径（2.184μm）均达到最小,平均晶粒尺寸达到15.2nm,球磨细化效果最佳,球磨30h,粒度峰右移且分布范围变宽.在球磨20h内,随球磨时间的延长,Cr粉的晶粒尺寸减小,显微应变增大,当晶粒尺寸达到15nm左右时,显微应变出现了突降,随后显微应变随着晶粒尺寸的减小而减小.Cr粉细化的机理是：球磨初期Cr粉产生强烈塑性变形,缺陷密度剧烈增加,粉体发生强烈加工硬化,加速了粉体碎化;球磨25h冷焊和碎化达到动态平衡,粉体粒度达到最小;球磨30h后,粉体表面活性增大,粉体出现再次团聚.机械球磨法可获得形状规则的类球形Cr颗粒.

英文摘要：

The temporal variation pattern of particle size distribution,grain size and microstrain of Cr powder in the process of mechanical ball milling were studied.The morphology characteristic and refinement mechanism of Cr powder in mechanical ball milling process are explored.The result shows that the Cr refinement will mainly occur in the early stage of the ball milling（5h）,and the refinement rate slows noticeably after 5h.Ball milled for 25 h,the surface area average particle size（1.383μm）and volume average particle size（2.184μm）of Cr powder become minimum,the average grain size being 15.2nm and the result of ball milling refinement being the best.Ball milled for 30 h,the peak of particle size will shift to the right and particle size distribution range will become wide.Within 20 hball milling,The grain size of Cr powder will decrease with the extension of ball milling time,and its microstrain will increase,meantime.When the grain size reaches around 15 nm,the microstrain will drop suddenly,then the microstrain will decrease with the decrease of the grain size.The refinement mechanism of Cr powder of is as follows：at the beginning of ball milling,a strong plastic deformation will take place with the Cr powder and strong work hardening takes place also in powder,speeding up the powder fragmentation.Cold welding and fragmentation will reach dynamic balance when the powder is milled for 25 h,powder particle size reaching its minimum.After 30 hmilling,the powder surface activity will increase and powders will reunite again.By means of mechanical ball milling,aquasi-global Cr particle with regular form can be obtained.