Design,preparation,microstructure and mechanical property of the lightweight radiation-shielding Mg-Ta-Al composites basing differential temperature hot rolling

A novel lightweight,radiation-shielding Mg-Ta-Al layered metal-matrix composite(LMC)was successful designed by doping the extremely refractory metal(Ta)into Mg sheets.These Mg-based LMCs sheets shows excellent radiation-dose shield effect,about 145 krad·a^(−1),which is about 17 times of traditional Mg alloy,while its surface density is only about 0.9 g·cm^(−2),reducing by 60%than that of pure Ta.The quantitate relationship between radiation-dose and the materials’thickness was also confirmed to the logistic function when the surface density is in the range of 0.6-1.5 g·cm^(−2).Meantime,the rolling parameters,interface microstructure and mechanical properties in both as-rolled and annealing treated samples were evaluated.The sheets possess a special dissimilar atoms diffusion transitional zone containing an obvious inter-diffusion Mg-Al interface and the unique micro-corrugated Ta-Al interface,as well as a thin Al film with a thickness of about 10μm.The special zone could reduce the stress concentration and enhance the strength of Mg-Ta-Al LMCs.The interface bonding strength reaches up to 54-76 MPa.The ultimate tensile strength(UTS)and yield strength(TYS)of the Mg-Ta-Al sheet were high to 413 MPa and 263 MPa,respectively,along with an elongation of 5.8%.The molecular dynamics(MD)analysis results show that the two interfaces exhibit different formation mechanism,the Mg-Al interface primarily depended on Mg/Al atoms diffusion basing point defects movement,while the Ta-Al interface with a micro-interlock pining shape formed by close-packed planes slipping during high temperature strain-induced deformation process.

废弃菌菇渣无害化处置工艺优化研究

为有效提高菇渣废弃物的无害化处置效率,进行了发酵菌剂的引选与无害化处置工艺优化研究,结果表明,菇渣中添加30%比例的牛粪或菇渣中添加10%以上的牛粪及3‰复合菌剂均能大大促进菇渣堆肥升温腐熟发酵过程,缩短物料无害化处置周期,随着处理时间的延长,物料pH表现出先上升后逐步下降的趋势。试验中香菇渣物料的发芽指数在无害化处理5天以后均达到了50%以上的安全范围。研究结论证明通过调节菇渣物料C/N及添加复合菌剂可以显著提高菇渣废弃物的无害化处置效率。

High-tenacity in-situ Ti/Zr-based bulk metallic glasses composites fabricated by industrial high-pressure die casting

The glass-forming ability and mechanical properties of metallic glasses and their composites are well known to be sensitive to the preparation conditions and are highly deteriorated by industrial preparing conditions such as low-purity raw materials and low vacuum.Here,we showed that a series of in-situ bulk metallic glass composites(BMGCs)which exhibit excellent ductility and segmental work hardening were successfully developed utilizing a high vacuum high-pressure die casting(HV-HPDC)technology along with industrial-grade raw materials.The tensile properties of these BMGCs are systematically investigated and correlated with the alloy microstructure.As compared with the copper mold suction casting method,the volume fraction difference of the dendrite phase for the BMGCs with the same composition is not significant when fabricated by the HV-HPDC,whereas the size of theβ-phase is generally larger.Insitu BMGCs with the composition of Ti_(48)Zr_(20)(V_(12/17)Cu_(5/17))19 Be 13 obtained by the HV-HPDC process show ductility up to 11.3%under tension at room temperature and exhibit a certain amount of work hardening.Two conditions need to be met to enable the BMGCs,which are prepared by vacuum die-casting to retain favorable ductility:(1)The volume fraction ofβphase stays below 62%±2%;(2)The equiaxed crystals with a more uniform size in the range of 5-10μm.Meanwhile,the results of the present study provided guidance for developing BMGCs with good ductile properties under industrial conditions.

简单易得的自氧化纳米泡沫镍用于高性能析氢和析氧催化

开发组成简单、无贵金属、制备简洁的自支撑析氢、析氧催化反应(HER和OER)催化剂是电解水的关键需求之一.本文以Mg_(80)Ni_(20)非晶合金薄带为前驱体,采用一步脱合金法制备了具有自支撑结构的自氧化纳米泡沫镍,在电流密度为10 mA cm^(-2)时HER和OER的过电位仅分别为33.1和330 mV,且均具有长达100 h的长期稳定性.基于纳米泡沫镍的水电解槽达到10 mA cm^(-2)的外加电压仅为1.58 V.纳米泡沫镍独特的三维超细多孔结构显著促进了其表观活性,同时其Ni/NiO复合结构显著提高了本征HER活性.本工作验证了纳米泡沫金属是一种有潜力的高性能催化材料.

Research on continuous core-filling casting forming process of copper-clad aluminum bimetal composite material

A single forming equipment of bimetal continuous core-filling casting was designed and manufactured for the purpose of developing copper-aluminum composite materials.The characteristics of the equipment were as follows：the crystallizer composed of water jacket copper sleeve in which graphite sleeve was set, two melting furnaces with different diameters vertically distributed, the low furnace of melting copper linked with the crystallizer, continuous casting and core-filling proceeded at the meantime.The rational processing parameters were determined through a series of experiments：contact length from down crucible to water-cooling cupreous crystallizer, 20 mm;length of recooling spray jet under crystallizer, 95 mm;temperature of copper and aluminum, 1250-1320℃ and 700℃ respectively;pulling rate, 16 mm/min.The qualified copper-clad aluminum composite rods, the external and inner diameter of which was 40 mm and 24 mm respectively, could be drawn successfully on that basis.Tested by hydrostatic extrusion and drawing process, the boss ratios of the copperclad aluminum composite rods were maintained a relatively stable scope of about 0.59-0.65, which was not obviously changed by subsequent plastic processing.

Deformation Mechanism in Fe_(61)Mn_(18)Si_(11)Cr_(10) Medium Entropy Alloy Under Different Strain Rates

We introduce a non-equiatomic Fe_(61)Mn_(18)Si_(11)Cr_(10) medium entropy alloy designed by subjecting it to transformation-induced plasticity upon deformation at room temperature. Microstructure characterization carried out using scanning electron microscopy(SEM), electron backscatter diffraction(EBSD), transmission electron microscopy(TEM) and X-ray diffraction(XRD) shows a homogeneous solid solution FCC + BCC structured dual phase. Investigations on the deformation substructures at specific strain levels via EBSD reveal the deformation-induced transformations of γ→α′ and γ→ ε. The strengths, particularly yield strength, of the designed alloy are found to be higher than these of the well-studied five component FeMnNiCoCr system for the introduction of the hard phase( α′-martensite). When tensile tests are performed at different strain rates of 10^(–4)s^(-1), 10^(–3)s^(-1), 10^(–2)s^(-1), the tested material exhibits a slightly negative strain rate sensitivity and work hardening rate sensitivity.