Evolution of precipitates in Mg−7Gd−3Y−1Nd−1Zn−0.5Zr alloy with fine plate-like 14H-LPSO structures aged at 240℃

The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr(wt.%)alloy with fine plate-like 14H-LPSO structures aged at 240℃were investigated using transmission electron microscopy(TEM)and high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).Fine plate-like 14H-LPSO structures precipitate after heat treatment at 500℃for 2 h,andβ-type phases precipitate after the alloy is aged at 240℃.The long-period atomic stacking sequence of 14H-LPSO structures along the[0001]αdirection is ABABCACACACBABA.After being aged at 240℃for 2 h,theβ-type phases are the ordered solution clusters,zig-zag GP zones,and a small number ofβ′phases.The peak hardness is obtained at 240℃for 18 h with a Brinell hardness of 112,theβ-type phases areβ’phases and local RE-rich structures.After being aged at 240℃for 100 h,theβ-type phases areβ’,β1 andβ’F phases.β′phases nucleate from the zig-zag GP zones directly withoutβ″phases,and then transform intoβ1 phase byβ’→β’F→β1 transformations.The Zn not only can form LPSO structure,but also is the constituent element ofβ1 phases.LPSO structures have a certain hindrance to the coarsening ofβ’andβ1 along<0001>α.

Precipitate evolution in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr alloy during isothermal ageing at 240 ℃

The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr alloy during isothermal ageing at 240 ℃ were investigated using transmission electron microscopy (TEM) and high-angle annular dark- eld scanning transmission electron microscopy (HAADF-STEM). After under-ageing for 2 h, the precipitates in the alloy are ordered solute clusters with rare earth atomic columns exhibiting hexagonal ring structure, zigzag GP zones and β' in its early formation. After peak-ageing for 18 h, the precipitates are mainly β' and new rod-like β'p accompanied with β'. After over-ageing for 100 h, the precipitates are β',β1, long-period stacking ordered (LPSO) building block known as γ′ and 14H-LPSO.β' has the three-dimensional shape of convex lens with smaller length-to-width ratio viewed along <0001>α than that in the EW75 alloy. The excellent thermal stability of this alloy can be attributed to the γ' and 14H-LPSO retarding the growth of β' and β1, low diffusion rate of rare earth atoms and physical character of β' and β1.

Enhancing strength and ductility in back extruded WE71 magnesium alloy cylindrical parts by introduction of multi-direction forging process

Magnesium cylindrical parts have relatively poor mechanical properties and distinct anisotropy of microstructure,which hinder their application as structural components.To improve the performance of WE71 cylindrical parts,multi-direction forging(MDF)was introduced before back extrusion,and the microstructure and mechanical properties were investigated.Results of microstructure show that the grain size in the outer of the cylindrical bottom is refined from 30.1 to 27.7μm,the micro structure is more uniform and the dislocation density is higher.The bimodal grain structure is formed in the outer of the cylindrical wall,which is ascribed to the formation of MgsRE phases along grain boundaries.These phases result in the Zener pinning effect on grain boundaries and the reduction of DRX volume fraction.The texture type of the cylindrical bottom is<0001>‖ED and the cylindrical wall is<1010>‖ED,and the maximum pole intensity is 1.986 and 1.664,respectively.Results of the tensile test at room temperature show that combined improved strength and ductility of the cylindrical part is attained after introducing the MDF process.The ultimate tensile strength(UTS),yield strength(YS)and elongation are279 MPa,185 MPa and 12%at the bottom and 299 MPa,212 MPa and 20%at the wall.

An outbreak of Mycobacterium marinum infection associated with handling seabass in China

To the Editor:Mycobacterium marinum is a nontuberculous mycobacterium that can cause opportunistic infections in humans,ranging from a single cutaneous lesion to disseminated disease.[1]It was first isolated from a fish in 1926 and identified as a cause of human infection in 1951.[1]The estimated annual incidence ranges from 0.04 to 0.27 per 100,000 persons in different countries.Outbreaks of M.marinum infections related to handling fish are not common,but have also been reported.

Viral suppression of type I interferon signaling by NSs of DBV,SFSV and UUKV via NSs-mediated RIG-I degradation

Phenuiviridae,a member of the Bunyavirales order,can lead to significant human morbidity and mortality.Various phenuiviruses target specific cellular proteins and have strategies to counteract the effects of type I interferon(IFN).Previous studies have shown that phenuiviruses infection inhibits the synthesis of type I IFNs,and viral nonstructural proteins(NSs)had been further identified as an IFN antagonist.This study found that the NSs proteins of Dabie bandavirus(DBV),Sandfly fever Sicilian virus(SFSV),and Uukuniemi virus(UUKV)can inhibit Sendai virus-induced activation of IFN-βpromoter and phosphorylation of IFN regulatory factor 3(IRF3).Moreover,detailed analysis revealed that the phenuivirus NSs protein could directly interact with retinoic acid inducible gene-I(RIG-I)and degrade it via a proteasome-dependent pathway.In short,this study demonstrate a novel mechanism of phenuiviruses to resist host antiviral immunity,which may help understand these pathogens and suggest novel therapeutic approaches.