CRYSTAL STRUCTURE OF LONG CHAIN COMPLEX OF [Cu(TTA)(4,4'-BIPYRIDINE)]_n

The crystal structure of[Cu(2-thienoyl-trifluoroacetone)(4,4—bipyridine)]_n was determined by X-ray diffraction analysis. The crystal belongs to monoclinie with the space group C2/c, Mr=440.91, a=9.640(5) A, b=24.97(1) A, c=16.032(7) A, β=106.76(3)°,V=3695(3) A^3, Z=8, Dc=1.58g/cm^3, F(000)=1776. Final R and Rw are 0.062 and 0.069, respectively. The local coordination geometry around Cu(I) ion is a distorted tetrahedron. Cu(TTA) are linked with 4,4-bipyridine, forming long chain in the crystal.

Microstructure and tribological behavior of Mg-Gd-Zn-Zr alloy with LPSO structure

A Mg-14.28Gd-2.44Zn-0.54Zr （mass fraction, %） alloy was prepared by conventional ingot metallurgy （I/M）. The microstructure differences in as-cast and solution-treated alloys were investigated. Sliding tribological behaviors of the as-cast and solution-treated alloys were investigated under oil lubricant condition by pin-on-disc configuration. The wear loss and friction coefficients were measured at a load of 40 N and sliding speeds of 30-300 mm/s with a sliding distance of 5000 m at room temperature. The results show that the as-cast alloy is mainly composed ofα-Mg solid solution, the lamellar 14H-type long period stacking ordered （LPSO） structure within matrix, andβ-[（Mg,Zn）3Gd] phase. However, most of theβ-phase transforms to X-phase with 14H-type LPSO structure after solution heat treatment at 773 K for 35 h （T4）. The solution-treated alloy presents low wear-resistance, because the hard β-phase is converted into thermally-stable, ductile and soft X-Mg12GdZn phase with LPSO structure in the alloy.

Design and research of gymnasium structure in Zhejiang University

This paper deals with the issues involved during the design of a complex gymnasium located at the new campus of Zhejiang University. The complexity comes from the gymnasium’s being of three parts: long-span membrane structure, prestressed concrete structure and extraordinarily long tubular steel structure without seams. The paper first presents considera- tions of the prestress design, followed by analyses of the stress states due to temperature changes and concrete shrinkage. Buckling and postbuckling analyses were performed to determine the load-carrying capacity of the perfect and imperfect tubular steel structure of the inclined arch system, while dynamic relaxation method and general nonlinear finite element analysis were used to carry out shape-finding and stress analyses of the membrane structure respectively. Finally, collated monitoring date was applied to control the construction quality and verify the design parameters. Some useful conclusions are available at the end of the paper.

Fabrication of NiTi Shape Memory Alloys with Graded Porosity to Imitate Human Long-bone Structure

Replacement of damaged long bones is still a significant challenge in surgery. In the present study, a NiTi Shape Memory Alloy （SMA） constructed with graded porosity imitating human long bone structure was fabricated via a dedicated moulding procedure. The outer layer （porosity 14 %） and inner layer （porosity 52 %） of the bone-like graded NiTi alloy were found to be co-axial very well with the interface with a good metallurgical bonding. Moreover, the compression strength and elastic modulus of the graded-porosity NiTi SMAs were found to be 360.6 MPa and 6.7 GPa, respectively, which have been improved by its coaxiality compared with the one with poor coaxiality. The graded-porosity NiTi SMAs exhibit resembling mechanical performance as human long-bones, and are considered to be better implant candidates for long bone replacement.

Dual phases strengthening behavior of Mg-10Gd-1Er-1Zn-0.6Zr alloy

The microstructure evolution and strengthening mechanisms of Mg-10Gd-1Er-1Zn-0.6Zr(wt.%) alloy were focused in the view of the size parameters and volume fraction(fp) of dual phases(long period stacking ordered(LPSO) structures and β’ precipitates).Results show that two types of LPSO phases with different morphologies formed,and the morphology and size of both LPSO phases varied with the solution conditions.However,the volume fraction decreased monotonously with increasing solution temperature,which in turn raised the volume fraction of β’ phase during aging.The alloy exhibited an ultimate tensile strength of 352 MPa,a yield strength of 271 MPa,and an elongation of 3.5% after solution treatment at 500℃ for 12 h and aging at 200℃ for 114 h.In contrast to the LPSO phase,the β’ phase seems to play a more important role in enhancing the yield strength,and consequently,a decreased fLPSO/fβ’,ratio results in an increased yield strength.

Direct Algorithms for Steady-State Solution of Long Slender Marine Structures

The steady state solution of long slender marine structures simply indicates the steady motion response to the excitation at top of the structure.It is very crucial especially for deep towing systems to find out how the towed body and towing cable work under certain towing speed.This paper has presented a direct algorithm using Runge-Kutta method for steady-state solution of long slender cylindrical structures and compared to the time iteration calculation;the direct algorithm spends much less time than the time-iteration scheme.Therefore, the direct algorithm proposed in this paper is quite efficient in providing credible reference for marine engineering applications.

Refining 18R-LPSO phase into sub-micron range by pre-kinking design and its prominent strengthening effect on Mg_(97)Y_(2)Zn_(1)alloy

In this study,a composite deformation strategy of pre-kinking(equal channel angular pressing(ECAP))followed by large-ratio hot extrusion(HE)was designed to refine the 18R long period stacking ordered(LPSO)phase into sub-micron range in a Mg_(97)Y_(2)Zn_(1)(at.%)alloy.After the composite processing,the mechanical properties of the alloy are significantly enhanced,superior to the majority of reported Mg_(97)Y_(2)Zn_(1) and other LPSO-containing Mg alloys.Among the composite deformed alloys,the 16P-HE alloy exhibits the best mechanical properties with tensile yield strength(TYS)of 475 MPa,ultimate tensile strength(UTS)of 526 MPa,and fracture elongation(FE)of 14.5%.Quantitative analysis of 18R phase indicates that increasing ECAP pass from 1 to 16 gradually decreases the average size of 18R phase from 5.1μm to 2.3μm.After HE,the 18R phase is further refined with a corresponding decrease in the average size in the descending order of 1P-HE(4.3μm),4P-HE(3.2μm),and 16P-HE(1.4μm)alloys.Calculation of the strengthening contributions confirms that the superior mechanical properties of 16P-HE alloy are mainly due to its strongest interface strengthening(145 MPa)and grain boundary strengthening(189 MPa)from the sub-micron 18R phase andα-Mg grains.Moreover,the strengthening effect of 18R phase decreases gradually with their morphology changing from particles to fibers,and to blocks.The obtained results further deepen and broaden the strengthening-toughening theory of 18R phase.

Characterization of microstructure in high strength Mg_(96)Y_3Zn_1 alloy processed by extrusion and equal channel angular pressing

The Mg96Y3Zn1 alloy processed by extrusion and equal channel angular pressing （ECAP） was investigated. It was found that the Mg96Y3Zn1 alloy processed by extrusion and ECAP obtained ultrafine grains and exhibited excellent mechanical properties. After ECAP, the average grain size of Mg96Y3Zn1 alloy was refined to about 400 nm. The highest strengths with yield strength of 381.45 MPa and ultimate tensile strength of 438.33 MPa were obtained after 2 passes at 623 K. The high strength of Mg96Y3Zn1 alloy was due to the strengthening by the grain refinement, the long period stacking （LPS） structure, solid solution, fine Mg24Y5 particles, and nano-scale precipitates. It was found that the elongation was decreased with pass number increasing. It was because that the cracks were preferentially initiated and propagated in the interior of X-phase during the tensile test.

Effects of Heat Treatments on Microstructures and Precipitation Behaviour of Mg_(94)Y_4Zn_2 Extruded Alloy

Microstructures and precipitation behaviours of Mg94Y4Zn2 （at. %） extruded alloy during solution treatment and ageing processes were investigated. Three major phases were observed in the as-cast Ug94Zn2Y4 alloy：α-Mg, block shaped 1 8R long period stacking ordered （LPSO） phase and Mg24Y5 cuboid particles. After homogenization and extrusion, the block shaped LPSO phase changed into plate-like shape aligned along the direction of extrusion. During solution treatment, a small fraction of LPSO phase was transformed from 18R structure to 14H type. The nano-scale β＇ phase with its close-packed planes being perpendicular to the direction of both α-Mg and LPSO structure was precipitated at ageing stage. The coexistence of β＇ and LPSO phase contributes to the strengthening of the alloy, with microhardness for the matrix and LPSO structures reaching 145.8 and 155,0 HV, respectively.