AZ31 magnesium alloy fibers reinforced poly（lactic-co-glycolic acid） （PLGA） composites were prepared and their mechanical property, immersion corrosion behavior and biocompatibility were studied. The tensile test ...AZ31 magnesium alloy fibers reinforced poly（lactic-co-glycolic acid） （PLGA） composites were prepared and their mechanical property, immersion corrosion behavior and biocompatibility were studied. The tensile test showed that with the addition of AZ31 fibers, the composites had a significant increment in tensile strength and elongation. For the direct cell attachment test, all the cells showed a healthy morphology and spread well on the experimental sample surfaces. The immersion results indicated that pH values of the immersion medium increased with increasing AZ31 fiber contents. All the in vitro experimental results indicated that this new kind of magnesium alloy fibers reinforced PLGA composites show a potential for future biomedical applications.展开更多
Hall-Petch relation was widely applied to evaluate the grain size effect on mechanical properties of metallic material. However, the sample size effect on the Hall-Petch relation was always ignored. In the present stu...Hall-Petch relation was widely applied to evaluate the grain size effect on mechanical properties of metallic material. However, the sample size effect on the Hall-Petch relation was always ignored. In the present study, the mechanical test and microstructure observation were performed to investigate the combined effects of grain and sample sizes on the deformation behaviors of gold microwires. The polycrystalline gold microwires with diameter of 16 ?m were annealed at temperatures from 100°C to 600°C, leading to different ratios(t/d) of wire diameter(t) to grain size(d) from 0.9 to 16.7. When the t/d was lower than 10, the yield stress dropped fast and deviated from the Hall-Petch relation. The free-surface grains played key role in the yield stress softening, and the volume fraction of free-surface grains increased with the t/d decreasing. Furthermore, the effects of t/d on work-hardening behaviors and fracture modes were also studied. With t/d value decreasing from 17 to 3.4, the samples exhibited necking fracture and the dislocation pile-ups induced work-hardening stage was gradually activated.With the t/d value further decreasing(t/d < 3.4), the fracture mode turned into shear failure, and the work-hardening capability lost. As the gold microwire for wire bonding is commonly applied in the packaging of integrated circuit chips, and the fabrication of microwire suffers multi-pass cold-drawing and annealing treatments to control the grain size. The present study could provide instructive suggestion for gold microwire fabrication and bonding processes.展开更多
基金supported by the National Basic Research Program of China(973 Program)(Grant Nos.2012CB619102 and 2012CB619103)the State Key Laboratory for Mechanical Behavior of Materials(Grant No.20111210)+3 种基金the National High Technology Research and Development Program of China(863 Program)(Grant No.2011AA030103)the Research Fund for the Doctoral Program of Higher Education(Grant No. 20100001110011)the National Natural Science Foundation of China(No.31170909)the National Science Fund for Distinguished Young Scholars(Grant No.51225101)
文摘AZ31 magnesium alloy fibers reinforced poly（lactic-co-glycolic acid） （PLGA） composites were prepared and their mechanical property, immersion corrosion behavior and biocompatibility were studied. The tensile test showed that with the addition of AZ31 fibers, the composites had a significant increment in tensile strength and elongation. For the direct cell attachment test, all the cells showed a healthy morphology and spread well on the experimental sample surfaces. The immersion results indicated that pH values of the immersion medium increased with increasing AZ31 fiber contents. All the in vitro experimental results indicated that this new kind of magnesium alloy fibers reinforced PLGA composites show a potential for future biomedical applications.
基金financially supported by the National Key R&D Program of China(Project No.2017YFA0204403)the Shenzhen Virtual University Park(R-IND1710)+5 种基金the Innovation and Technology Commission via the Hong Kong Branch of National Precious Metals Material Engineering Research Centersupported by the Research Grants Council of the Hong Kong Special Administrative Region,China(No.CityU 11209914)General Research Fund of Hong Kong(No.CityU 11247516)the National Natural Science Foundation of China(No.51301147)supported by Province-Institute/Province-College Cooperation Project underGrant No.2017IB016The financial support from SZSTI(Ref:JSGG20141020103826038)
文摘Hall-Petch relation was widely applied to evaluate the grain size effect on mechanical properties of metallic material. However, the sample size effect on the Hall-Petch relation was always ignored. In the present study, the mechanical test and microstructure observation were performed to investigate the combined effects of grain and sample sizes on the deformation behaviors of gold microwires. The polycrystalline gold microwires with diameter of 16 ?m were annealed at temperatures from 100°C to 600°C, leading to different ratios(t/d) of wire diameter(t) to grain size(d) from 0.9 to 16.7. When the t/d was lower than 10, the yield stress dropped fast and deviated from the Hall-Petch relation. The free-surface grains played key role in the yield stress softening, and the volume fraction of free-surface grains increased with the t/d decreasing. Furthermore, the effects of t/d on work-hardening behaviors and fracture modes were also studied. With t/d value decreasing from 17 to 3.4, the samples exhibited necking fracture and the dislocation pile-ups induced work-hardening stage was gradually activated.With the t/d value further decreasing(t/d < 3.4), the fracture mode turned into shear failure, and the work-hardening capability lost. As the gold microwire for wire bonding is commonly applied in the packaging of integrated circuit chips, and the fabrication of microwire suffers multi-pass cold-drawing and annealing treatments to control the grain size. The present study could provide instructive suggestion for gold microwire fabrication and bonding processes.
