Separation of primary Si and impurity boron removal from Al-30%Si-10%Sn melt under a traveling magnetic field

Separation of primary Si phase and removal of boron in the primary Si phase during the solidification process of the Al-30%Si-10%Sn melt under a traveling magnetic field(TMF) were investigated. The results showed that the agglomeration layer of the primary Si can be formed in the periphery of the ingot while the inner microstructures mainly consist of the eutectic α-Al+Si and β-Sn phases. The intense melt flow carries the bulk liquid with higher Si content to promote the growth of the primary Si phase which is first precipitated close to the inner wall of crucible with a relatively lower temperature, resulting in the remarkable segregation of the primary Si phase. The content of impurity B in the primary Si phase can be removed effectively with an increase in magnetic flux intensity. The results of electron probe microanalysis(EPMA) clearly indicated that the average intensity of the B Ka line in the α-Al phase region of Al-Si-Sn alloy is higher in the case of solidification under TMF than that of normal solidification condition, suggesting that the electromagnetic stirring can promote the B removal from the primary Si phase.

Boron removal from molten silicon using CaO-SiO_2-BaO-CaF_2 slag

The distribution coefficient (LB) of boron between CaO?SiO2?BaO?CaF2 slag and silicon was investigated usingelectromagnetic induction melting for the purpose of improving the boron removal fraction. The dependence of the borondistribution coefficient between slag and silicon on the fundamental parameters of CaO to SiO2 mass ratio and refining time and theadditions of BaO and CaF2 to the slag was discussed. The results show that LB can be increased by adding BaO and CaF2 toCaO?SiO2 slag. The maximum value of LB (6.94) is obtained when the CaO to SiO2 mass ratio is 1.1:1 and the contents of BaO andCaF2 are fixed at 15% and 20%, respectively. Increasing the refining time increases the LB. After the slag treatment is performedtwice, the boron content of the silicon is successfully reduced from 3.5×10?5 to 3.7×10?6, and the removal fraction of boron reaches89.4%.

Biodegradable Zn-0.5Li alloy rib plate:Processing procedure development and in vitro performance evaluation

Trauma kills more than four million people worldwide each year,with chest trauma accounting for 25%of these deaths.Rib fractures are the main manifestation of chest trauma.Biodegradable Zn alloys offer a new option to overcome clinical problems caused by permanent rib fracture internal fixation mate-rials,e.g.,long-term stress masking and secondary surgery.In this study,the fabrication procedure of biodegradable Zn-0.5Li alloy rib plates is successfully developed,which consists of casting,hot-warm rolling,cutting,and pressing sequentially.Biomechanical three-point bending performance of the Zn al-loy rib plates is comparable to that of commercial pure Ti rib plates,much higher than that of pure Zn rib plates.In addition,the Zn alloy exhibits the best antibacterial ability against E.coli and S.aureus among the three materials.Although the Zn alloy exhibits a weaker MC3T3 cytocompatibility than pure Ti,it is better than pure Zn.This study provides a foundation for the future development of various biodegrad-able Zn alloy rib plates.

Clinical significance of nuchal translucency measurement in routine prenatal examination

To the Editor:Measurement of nuchal translucency(NT)is a validated marker for aneuploidy,fetal abnormalities,and other pathologic conditions,[1] which makes it crucial to ensure the accuracy of NT measurement in clinical treatment.Ever since 2012,all the pregnant women visiting our hospital(The International Peace Maternity&Child Health Hospital Affliated to Shanghai Jiao Tong University School of Medicine,China)need to receive a routine first-trimester sonographic marker assessment.

300 MPa grade highly ductile biodegradable Zn-2Cu-(0.2-0.8)Li alloys with novel ternary phases

Although a few high-strength biodegradable Zn alloys with yield strengths(YSs)over 300 MPa in rolled state have been developed,their elongations(ELs)are generally less than 30%.This study developed rolled Zn-2Cu-x Li(x=0.2 wt.%,0.5 wt.%,0.8 wt.%)alloys with YSs of 316-335 MPa and ELs of 44%-61%.Three-dimensional atom probe(3DAP)and time of flight secondary ion mass spectrometry(TOF-SIMS)were employed to characterize Li distribution.Three kinds of Zn-Cu-Li ternary phases are identified,which are blockyε′-(Cu_(0.5),Li_(0.5))Zn 4,blockyβ′-(Li_(0.9),Cu_(0.1))Zn 4,and small roundγparticles with high Li content in the annealed state.Other identified phases are Zn,β-LiZn 4,andε-CuZn 4 phases.With the increase of Li content in the alloys,ε′phase with 6.50 at.%Cu transforms intoβ′phase with 2.12 at.%Cu,i.e.,the average level in the alloys.Withinε′phase,there exist nano-scale Li clusters andεphase,resulting inε′/εstructure.Dense Zn laths precipitate fromβ′phase,resulting inβ′/Zn lamellar structure.The lamel-lar structure is the matrix of Zn-2Cu-0.8Li and leads to near-isotropic plasticity.Electrochemistry tests show that degradation rates fall in the range of 153-196μm/year,which decrease with Li content.All the alloys exert positive effects on the growth of MC3T3-E1 cells with 10%extract.This research reveals how microstructure evolves in Zn-2Cu-x Li alloys,which lays the foundation for their future applications.