Phase transformation behavior of Ti49Ni49.5Fe1V0.5 and Ti48Ni48.5Fe1V2.5 alloys after different heat treatments简

The effects of heat treatments on the phase transformation behavior of Ti49 Ni49.5 Fe1 V0.5 and Ti48 Ni48.5 Fe1 V2.5 alloys were investigated. The results indicate that the alloys subjected to different heat treatments have B2 structure at room temperature. All the specimens exhibit a twostage B2→R→B190martensitic transformation on cooling, but a B190→B2 one-stage reverse martensitic transformation on heating except aged A1 alloy, which undergoes an abnormal two-stage transformation upon heating. The phase transformation temperatures are affected by heat treatments and V content, which can be attributed to the variation of the second-phase particles content in the matrix.     

Phase transformation and thermal analysis during combustion synthesis of Mg17Al12 alloy简

The Mg–Al hydrogen storage alloy was successfully prepared by combustion synthesis(CS) method. The formation of alloy phases during the CS process was studied using X-ray diffraction(XRD), scanning electron microscope(SEM), and differential scanning calorimetry(DSC). When the time increases from 0, 0.5, 1.0 to 2.0 h at 733 K, the products are Mg and Al; Mg2 Al3, Mg and Al; Mg17 Al12, Mg2 Al3; and Mg; and eventually only Mg17 Al12, respectively. Combined with three peaks in the DSC traces, it is concluded that the formation of Mg17 Al12 during the CS includes three processes, namely, the formation of Mg2 Al3 first; then the unsaturated solid solution, Mg17 Al12; and finally the complete Mg17 Al12 alloy. The formation of Mg2 Al3 prior to Mg17 Al12 in this work is different from those prepared by mechanical alloying. This is thought to be related to the instant high temperature during the thermal explosion of CS.     

Crystal structure and magnetic properties of SmFe9-xCox alloys简

The crystal structure and magnetic properties of SmFe9-x Cox(x = 0, 1, 3, 5) alloys were studied by X-ray powder diffraction(XRD) and magnetic measurements. The Th2 Zn17-type structure of the as-cast state is changed to TbCu7-type structure after quenching to a rotating molybdenum roll under certain velocity(12, 20, and 32 m s-1). The(002) XRD peak appears and a-Fe phase disappears when the Co is added up to x = 5. Saturation magnetization of SmFe9 under different temperature shows 9 % change(112–102 A m2 g-1) when the temperature is higher than 200 K. The saturation magnetization is 115 A m2 g-1and coercivity is 0.304 T at 5 K for SmFe9 alloys. Increased saturation magnetization and decreased coercivity can be obtained for Co added up to x = 5 at 5 K.     

Pore structure and mechanical properties of directionally solidi ed porous aluminum alloys简

Porous aluminum alloys produced by the metal-gas eutectic method or GASAR process need to be performed under a certain pressure of hydrogen,and to carry over melt to a tailor-made apparatus that ensures directional solidification.Hydrogen is driven out of the melt,and then the quasi-cylindrical pores normal to the solidification front are usually formed.In the research,the effects of processing parameters （saturation pressure,solidification pressure,temperature,and holding time） on the pore structure and porosity of porous aluminum alloys were analyzed.The mechanical properties of Al-Mg alloys were studied by the compressive tests,and the advantages of the porous structure were indicated.By using the GASAR method,pure aluminum,Al-3wt.％Mg,Al-6wt.％Mg and Al-35wt.％Mg alloys with oriented pores have been successfully produced under processing conditions of varying gas pressure,and the relationship between the final pore structure and the solidification pressure,as well as the influences of Mg quantity on the pore size,porosity and mechanical properties of AlMg alloy were investigated.The results show that a higher pressure of solidification tends to yield smaller pores in aluminum and its alloys.In the case of Al-Mg alloys,it was proved that with the increasing of Mg amount,the mechanical properties of the alloys sharply deteriorate.However,since Al-3％Mg and Al-6wt.％Mg alloys are ductile metals,their porous samples have greater compressive strength than that of the dense samples due to the existence of pores.It gives the opportunity to use them in industry at the same conditions as dense alloys with savings in weight and material consumption.     

Processing stages of Gd2Sr(Al1-xFex)2O7 series简

The continuous series of perovskite-related oxides with the general formula GdzSr（Al1-xFex）207 0 〈 x 〈 1 were prepared by conventional ceramic technology in air. The pro- cessing stages of Gd2Sr（Al1-xFex）207 0 〈 x 〈 1 phases were investigated by means of X-ray powder diffraction （XRD） and scanning electron microscopy （SEM） with the element phase analysis. The three main stages of GdeSr（All_~Fex）aO7 for- marion are pointed out. The analysis of the mutual influence of intermediate compounds on the synthesis of the target solid solutions of complex composition, in particular for Gd2Sr（All-xFex）207 was carried out. It is determined that the closeness of the reactive mixture composition to the composition of individual compounds Gd2SrA1207 or GdaSrFeaO7 is of importance for the realization of a partic- ular way of GdESr（Al1-xFex）207 solid solutions formation. It is shown that at x ,= 0.2 the reversing in scheme of Gd2Sr（Al1-Fex）207 series formation is observed. The formation of the Gd2Sr（Al1-xFex）207 continuous series is indicated by the monotonic dependence of molar unit cell volume on the iron content x.     

0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5,Ti0.5)O3（1-x）(Ni51.5Mn25Ga23.5)x固溶体系磁电性能研究

采用传统的固相烧结法合成了0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5,Ti0.5)O3(1-x)(Ni51.5Mn25Ga23.5)x复合体系陶瓷。XRD结果表明,随着Ni51.5Mn25Ga23.5(NMG)掺入,Ni51.5Mn25Ga23.5先溶于0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5,Ti0.5)O3中,后NMG量超过5%不溶于复合体系中,使得0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5,Ti0.5)O3的峰位向右偏移;铁电性能测试结果表明,0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5,Ti0.5)O3(1-x)(Ni51.5Mn25Ga23.5)x复合体系陶瓷随着Ni51.5Mn25Ga23.5的掺入量的增加矫顽场E先降低后增加,剩余极化强度Pr逐渐降低,这与XRD的测试结果相一致;磁性测试结果表明,0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr0.5,Ti0.5)O3(1-x)(Ni51.5Mn25Ga23.5)x随着Ni51.5Mn25Ga23.5掺入量的增加,以独立相析出在复合体系中,剩余磁化强度Mr逐渐增大。     

Microstructure and hardness of WC-Co particle reinforced iron matrix surface composite简

In this study, a high Cr cast iron surface composite material reinforced with WC-Co particles 2-6 mm in size was prepared using a pressureless sand mold infiltration casting technique. The composition, microstructure and hardness were determined by means of energy dispersive spectrometry （EDS）, electron probe microanalysis （EPMA）, scanning electron microscope （SEM） and Rockwell hardness measurements. It is determined that the obtained composite layer is about 15 mm thick with a WC-Co particle volumetric fraction of -38%. During solidification, interface reaction takes place between WC-Co particles and high chromium cast iron. Melting and dissolving of prefabricated particles are also found, suggesting that local Co melting and diffusion play an important role in promoting interface metallurgical bonding. The composite layer is composed of ferrite and a series of carbides, such as （Cr, W, Fe）23C6, WC, W2C, M6C and M12C. The inhomogeneous hardness in the obtained composite material shows a gradient decrease from the particle reinforced metal matrix composite layer to the matrix layer. The maximum hardness of 86.3 HRA （69.5 HRC） is obtained on the particle reinforced surface, strongly indicating that the composite can be used as wear resistant material.     

Microstructure and tensile properties of Mo alloy synthetically strengthened by nano-Y2O3 and nano-CeO2简

Nano-Y2 O3 and nano-CeO2 of different weight ratio mixed with deionizing water were doped into MoO2 powder by liquid–solid doping method. The diameter 1.80 and 0.18 mm alloy wires of Mo–0.3Y, Mo–0.3Ce, and Mo–0.15Y–0.15Ce were prepared through reduction, isostatic pressing, sintering, and drawing. Tensile properties, second phase microstructure and fracture surface appearance of wires were analyzed. The better refining effect for Mo alloy powder can be gotten after two kinds of nanoparticle oxide doped into MoO2 than only one doped. Nano-Y2 O3 and nano-CeO2 have different influences on sintering process. For nano-CeO2, the constraining effect of grain growth focuses on the initial sintering stage, nanoY2 O3 plays refining grains roles in the later densification stage. Nano-Y2 O3 is undistorted and keeps intact in the process of drawing; and nano-CeO2 is elongated and broken into parts in the drawing direction. The strengthening effect of nano-Y2 O3 and nano-CeO2 keeps the finer grains and superior tensile properties for Mo–0.15Y–0.15Ce wire.     

Microstructure evolution and room temperature deformation of a directionally solidiied Nb-Si-Ti-Cr-Al-Hf-Y alloy简

An Nb-14Si-22Ti-4Cr-2AI-2Hf-0.15Y（at.%） alloy was prepared by directional solidification （DS） with liquid metal cooling, and the withdrawal rates selected were 1.2, 6, and 18 mm-min1, respectively. The Influence of withdrawal rate and heat treatment on the microstructural evolution, fracture toughness and tensile strength at room temperature were investigated. Results show that the directionally solidified microstructure is composed of primary （Nb, X）ss dendrites and （Nb, X）ss/a-（Nb, X）5Si3 eutectic cells aligning with the growth direction. The formation of bulk Nb3Si is suppressed. With an increase in withdrawal rate, the dendrite arm spacing of （Nb, X）ss decreases, and the （Nb, X）ss/a-（Nb, X）5Si3 eutectic cells become finer and distribute homogeneously. Directional solidification can significantly improve the room temperature fracture toughness, especially the alloy with a withdrawal rate of 6 mm.min-1; its average value reaches 14.1 MPa.m^0.5, about 34% higher than that of the alloy without directional solidification. The withdrawal rate has obvious effect on tensile strength, and the tensile strength is improved from 200 MPa to 429 MPa as the withdrawal rate increases from 1.2 mm.min-1 to 1.8 mm-min-1. After heat treatment, the primary （Nb, X）ss branches become coarser; both the room temperature fracture toughness and tensile strength of the alloys solidified at 1.2 and 6 mm.min 1 are somewhat lower than the corresponding values of the alloy without heat treatment, while they are higher than the corresponding values of the alloy without heat treatment when solidified at 18 mm-min4.     

Morphology-structure diversity of ZnS nanostructures and their optical properties简

ZnS nanostructures with different dimensions and structure-related properties were reviewed in this paper. The crystallization of nanostructures from 0D, 1D to 3D, as well as the heterogonous counterparts, was sum- marized in the aspect of zinc blende, wurtzite structure, and their combinations. Furthermore, the structure-related energy bands and the corresponding photoelectric properties of ZnS nanostructures were also focused, in which we made a brief summary of the co-relations between photoluminescence and crystallography, especially the defectrelated luminescence properties of ZnS nanocrystal.     

Peak wavelength selection guides of chip and phosphors for phosphor-converted white light-emitting diodes简

The dependences of light efficiency of radiation （LER） and color-rendering index （CRI） of trichromatic white light-emitting diode （wLED）, composed of blue LED die, green/yellow, and red phosphors, on the peak wave- length of each primary were investigated by theoretical calculations, at correlative color temperature （CCT） from 2,700 to 6,500 K. The peak wavelength of InGaN based blue LED chip ranges from 450 to 471 nm, while those of Ca3Sc2Si3012：Ce3＋, b-SiA1ON：Eu2＋, and Y3A15012：Ce3＋ based green/yellow phosphors range from 511 to 572 nm, and those of Sr2SisN8：Eu2＋ and CaA1SiN3：Eu2＋ red phosphors range from 620 to 650 nm, which cover almost all the practically used, commercially available wave bands until now. Then, based on the results, selection guides of peak wavelengths for blue LED chip and phosphors to obtain tradeoff LER 〉280 lm.W-1 as well as CRI 〉80 in all CCTs are proposed. The favorable wave bands of each primary are suggested.     

Effect of centrifugal counter-gravity casting on solidification microstructure and mechanical properties of A357 aluminum alloy简

To investigate the influence of Centrifugal Counter-gravity Casting(C3) process on the solidification microstructure and mechanical properties of the casting, A357 aluminum alloy samples were produced by different process conditions under C3. The results show that C3 has better feeding capacity compared with the vacuum suction casting; and that the mechanical vibration and the convection of melts formed at the centrifugal rotation stage suppress the growth of dendrites, subsequently resulting in the refinement of grains and the improvement of mechanical properties, density and hardness. A finer grain and higher strength can be obtained in the A357 alloy by increasing centrifugal radius and rotational speed. However, casting defects will appear near the rotational axis and the mechanical properties will decrease once the rotational speed exceeds 150 r·min-1.     

The award ceremony and recipients of the Third "China Foundry Lifetime Achievement Award" and "China Foundry Outstanding Contribution Award"简

The China Foundry Lifetime Achievement Award and the China Foundry Outstanding Contribution Award established by the Foundry Institution of Chinese Mechanical Engineering Society （FICMES） are to honor those foundrymen who have made outstanding achievements and contributions to China＇s foundry industry. In 2013, the FICMES recognized four people for their work by granting each award to two people. The FICMES awarded the Third ＂China Foundry Lifetime Achievement Award＂ to Prof. Fu Hengzhi of Northwestern Polytechnical University, Harbin Institute of Technology as well as Henan Science and Technology University, a member of Chinese Academy of Engineering;     

Inhomogeneity of microstructure and mechanical properties of a 500 mm diameter heavy section semi-continuous cast AZ61 magnesium alloy ingot简

For the large magnesium alloy ingot, there is a considerable difference in cooling rate of different parts in the ingot, which leads to non-uniform distribution of the secondary phases, solute segregation and tensile properties. In the present research, an heavy AZ61 alloy ingot with a diameter of 500 mm was made by semi-continuous casting. The microstructure and mechanical properties at different positions along the radial direction of the large ingot were investigated by using an optical microscope(OM), a scanning electron microscope(SEM), an energy dispersive spectroscope(EDS), and a micro-hardness tester. The results indicate that the microstructure of the AZ61 ingot is non-uniform in different locations. It changes from equiaxed to columnar grains from the center to the edge; the average grain size gradually reduces from 1,005 μm to 763 μm, the secondary dendrite arm spacing reduces from 78 μm to 50 μm, and the Mg17(Al,Zn)12 phase is also refined. The micro-hardness value increases from 55.4 HV at the center to 72.5 HV at the edge of the ingot due to the microstructure differences, and the distribution of micro-hardness at the edge of the ingot is more uniform than that in the center. The tensile properties at room temperature show little difference from the center to the edge of the ingot except that the elongation at the edge is only 3.5%, much lower than that at other areas. The fracture mechanism is ductile fracture at the center and cleavage fracture at the edge of the ingot, and at the 1/2 radius of the ingot, a mixture of ductile and cleavage fracture is present.