Surface modification,as a promising approach to improve biocompatibility of biomaterials,has captured extensive close attention among many researchers.Here,micro-milling technology was used in constructing pyramid mic...Surface modification,as a promising approach to improve biocompatibility of biomaterials,has captured extensive close attention among many researchers.Here,micro-milling technology was used in constructing pyramid micro-structures on the surface of Ti-6Al-4Vimplant.Cutting parameters,including spindle speed,feed rate and depth of cut,were optimized to control the generation of burrs.In addition,low melting point alloy was selected to extend the boundary of the workpiece as supporting material to prevent the generation of top burrs.The surface topographies were characterized using scanning electron microscope and laser scanning microscope.Results showed that the dimension of burrs decreased with the decrease of depth of cut,and the size of burrs decreased with the increase of feed rate.Moreover,burrs nearly not appeared on both sides of the micro-grooves machined with low melting point alloy(LMPA)coating.Pyramid micro-structure on the workpiece surface was built successfully by combining optimized cutting parameters(S=35kr/min,Vf=60mm/min,ap=5μm)and LMPA coating.展开更多
Introducing heterogeneities into the structure is an effective way to enhance the plasticity in metallic glasses (MGs). As natural heterogeneity, the original randomly distributed free volume in MGs has been found to ...Introducing heterogeneities into the structure is an effective way to enhance the plasticity in metallic glasses (MGs). As natural heterogeneity, the original randomly distributed free volume in MGs has been found to be in favor of plasticity. However, the exact correlation between the free volume distribution and mechanical response is still unclear. In this paper, we investigate the shear banding in MGs with different structural disorders, characterized by both the free volume concentration (FVC) and the free volume dispersion (FVD). It is found that, either high FVC or wide FVD leads to low activation stress of shear band; wide FVD promotes the multiplication of shear bands but high FVC restricts it. It reveals that the yield strength in MGs is dependent on the amount of free volume while the plasticity mainly relies on the distribution. An optimum combination of the two aspects probably helps to design a MG of both good plasticity and high strength.展开更多
基金supported by the National Natural Science Foundations of China(Nos.51175306,51425503)the Tai Shan Scholar Foundation,the Fundamental Research Funds for the Central Universities(No.2014JC020)the Opening fund of State Key Laboratory of Nonlinear Mechanics
文摘Surface modification,as a promising approach to improve biocompatibility of biomaterials,has captured extensive close attention among many researchers.Here,micro-milling technology was used in constructing pyramid micro-structures on the surface of Ti-6Al-4Vimplant.Cutting parameters,including spindle speed,feed rate and depth of cut,were optimized to control the generation of burrs.In addition,low melting point alloy was selected to extend the boundary of the workpiece as supporting material to prevent the generation of top burrs.The surface topographies were characterized using scanning electron microscope and laser scanning microscope.Results showed that the dimension of burrs decreased with the decrease of depth of cut,and the size of burrs decreased with the increase of feed rate.Moreover,burrs nearly not appeared on both sides of the micro-grooves machined with low melting point alloy(LMPA)coating.Pyramid micro-structure on the workpiece surface was built successfully by combining optimized cutting parameters(S=35kr/min,Vf=60mm/min,ap=5μm)and LMPA coating.
基金supported by the National Natural Science Foundation of China (Grants Nos. 10725211, 11002144, 11021262)the National Natural Science Foundation of China-NSAF (Grant No. 10976100)+1 种基金the National Key Basic Research Program of China (Grant No. 2009CB724401)the Key Project of Chinese Academy of Sciences (Grant No. KJCX2-YW-M04)
文摘Introducing heterogeneities into the structure is an effective way to enhance the plasticity in metallic glasses (MGs). As natural heterogeneity, the original randomly distributed free volume in MGs has been found to be in favor of plasticity. However, the exact correlation between the free volume distribution and mechanical response is still unclear. In this paper, we investigate the shear banding in MGs with different structural disorders, characterized by both the free volume concentration (FVC) and the free volume dispersion (FVD). It is found that, either high FVC or wide FVD leads to low activation stress of shear band; wide FVD promotes the multiplication of shear bands but high FVC restricts it. It reveals that the yield strength in MGs is dependent on the amount of free volume while the plasticity mainly relies on the distribution. An optimum combination of the two aspects probably helps to design a MG of both good plasticity and high strength.
