Evolution of mechanical properties,localized corrosion resistance and microstructure of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging

The evolution of mechanical properties,localized corrosion resistance of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging(NIA)was investigated by hardness test,electrical conductivity test,tensile test,intergranular corrosion test,exfoliation corrosion test,slow strain rate tensile test and electrochemical test,and the mechanism has been discussed based on microstructure examination by optical microscopy,electron back scattered diffraction,scanning electron microscopy and scanning transmission electron microscopy.The NIA treatment includes a heating stage from 40℃to 180℃with a rate of 20℃/h and a cooling stage from 180℃to 40℃with a rate of 10℃/h.The results show that the hardness and strength increase rapidly during the heating stage of NIA since the increasing temperature favors the nucleation and the growth of strengthening precipitates and promotes the transformation of Guinier-Preston(GPI)zones toη'phase.During the cooling stage,the sizes ofη'phase increase with a little change in the number density,leading to a further slight increase of the hardness and strength.As NIA proceeds,the corroded morphology in the alloy changes from a layering feature to a wavy feature,the maximum corrosion depth decreases,and the reason has been analyzed based on the microstructural and microchemical feature of precipitates at grain boundaries and subgrain boundaries.

Sources of the Laoxiongdong carbonate-hosted Pb–Zn deposit in Southwest China:constraints from S–Pb–Zn isotopic compositions

The Sichuan-Yunnan-Guizhou(SYG)Pb-Zn mineral province,which has significant Pb-Zn repositories in China,is situated in the western Yangtze Block.Despite decades of research,the Pb-Zn source of deposits is still disputed between the basement rocks,sedimentary wall rocks,or the Emeishan flood basalts.The newly-discovered Laoxiongdong Pb-Zn deposit is hosted by the Late Ediacaran Dengying Formation in the SYG province.Moreover,the Laoxiongdong orebodies lie between regional deep faults and close to the Proterozoic basement and Emeishan basalts.Hence,this deposit represents a good case study on the ore-forming material source for the regional Pb-Zn mineralization.The Laoxiongdong Pb-Zn ores are massive,vein,or disseminated and have mainly sphalerite,galena,pyrite,quartz,and calcite.In this paper,we present new sulfide S-Pb-Zn isotope data of the deposit.The sulfideδ34SCDT values(+11.8 to+16.5‰)suggest that the reduced sulfur was mainly sourced from evaporites in the Late Ediacaran-Cambrian sequences.Pb isotopic ratios(206Pb/204Pb=18.004-18.107,207Pb/204Pb=15.652-15.667,and 208Pb/204Pb=38.037-38.248)suggest that the lead metal was primarily originated from the basement rocks.The sphaleriteδ66Zn values(+0.16 to+0.37‰)are also highly similar(within error)to those of basement rocks(+0.10 to+0.34‰),suggesting a basement-rocks zinc source with minor contributions from the carbonate host rocks and Emeishan flood basalts.The narrow sphalerite Zn isotopic range(0.21‰)also indicates that the Zn isotopic fractionation between the sphalerite and initial fluid was limited during the sphalerite ore precipitation.Therefore,we propose that both the Late Ediacaran Dengying Formation rocks and Proterozoic basement rocks were important ore-forming material source for the Laoxiongdong deposit,whereas the Emeishan flood basalts represent only a minor ore-material source.

Tennantite and Enargite Rejection in the Copper Flotation—A Mini-Review

With the development of arsenic removal technologies, biological method and sulfide method have been applied in industrial fields, other methods have also been applied in arsenic-containing copper flotation, including coagulation process, ion exchange method, direct precipitation method and so on. In the paper, a short review on the progress of arsenic removal technologies of copper flotation during the last decade is presented, and the importance and the trend of arsenic removal are discussed. The existing and possible strategies of improving copper recovery in porphyry copper ores and rejection of penalty elements such as Tennantite and Enargite in copper flotation concentrates are also presented.

Thermodynamic behaviors of SiCl_2 in silicon deposition by gas phase zinc reduction of silicon tetrachloride

The modified Siemens process,which is the major process of producing polycrystalline silicon through current technologies,is a high temperature,slow,semi-batch process and the product is expensive primarily due to the large energy consumption.Therefore,the zinc reduction process,which can produce solar-grade silicon in a cost effective manner,should be redeveloped for these conditions.The SiCl2 generation ratio,which stands for the degree of the side reactions,can be decomposed to SiCl4 and ZnCl2 in gas phase zinc atmosphere in the exit where the temperature is very low.Therefore,the lower SiCl2 generation ratio is profitable with lower power consumption.Based on the thermodynamic data for the related pure substances,the relations of the SiCl2 generation ratio and pressure,temperature and the feed molar ratio（n（Zn）/n（SiCl4） are investigated and the graphs thereof are plotted.And the diagrams of Kpθ-T at standard atmosphere pressure have been plotted to account for the influence of temperature on the SiCl2 generation ratio.Furthermore,the diagram of Kpθ-T at different pressures have also been plotted to give an interpretation of the influence of pressure on the SiCl2 generation ratio.The results show that SiCl2 generation ratio increases with increasing temperature,and the higher pressure and excess gas phase zinc can restrict SiCl2 generation ratio.Finally,suitable operational conditions in the practical process of polycrystalline silicon manufacture by gas phase zinc reduction of SiCl4 have been established with 1200 K,0.2 MPa and the feed molar ratio（n（Zn） /n（SiCl4）） of 4 at the entrance.Under these conditions,SiCl2 generation ratio is very low,which indicates that the side reactions can be restricted and the energy consumption is reasonable.

Effects of pre-deformation mode and strain on creep aging bend-forming process of Al-Cu-Li alloy

The bending deformation method was adopted to characterize the creep deformation behavior of Al-Cu-Li alloy in the creep aging forming(CAF) process based on a series of CAF tests, and the evolution laws of its mechanical properties and microstructures under different pre-deformation conditions were studied. The results show that the bending creep strain characterization method can intuitively describe the creep variation. With the increase of the pre-deformation strain, the creep strain of the specimen firstly increases and then decreases. The increase of the pre-deformation strain can promote the course of aging precipitation, and improve the formed alloy’s tensile properties at room temperature, the Kahn tearing properties, and the fatigue propagation properties. Pre-rolled specimens produce a slightly weaker work hardening than pre-stretched specimens, but they also create a stronger aging-strengthening effect;thus the strength, toughness and damage performance can be improved to some extent. Among all the types of specimens, the specimen with 3% rolling after CAF treatment has the best comprehensive mechanical properties.

Phosphogypsum Pyrolysis by Adding Mineralization Agent:Process and Mechanism

In order to decrease energy consumption for phosphogypsum(PG)pyrolysis process,a pilot-scale vertical-retort furnace was designed initiatively,and then mineralization agent was added to pyrolysis mixture.Calcium fluoride(CaF_(2))was proven to be a suitable mineralization agent,and the optimal parameters were:pyrolysis temperature 960℃,carbon-sulfur mole ratio 0.7,reaction time 50 min,and CaF_(2)dosage 4%by weight.Under this condition,PG decomposition and sulfur dioxide(SO_(2))conversion were up to 89.6%and 67.3%,respectively.CaF_(2)could lead to the formation of fluosilicate complexes,and facilitate PG decomposition at a low temperature.During pyrolysis process,calcium sulfide(CaS)was an inevitable intermediate substance,and only a part of total sulfur in the feedstock could be converted to SO_(2).

A CFD model for gas uniform distribution in turbulent flow for the production of titanium pigment in chloride process

The fluid dynamic behavior of feeding gas （TiCI4） in an annular channel affects the combination of 02 and TiCI4 in an oxidation reactor, a key piece of equipment in titanium pigment production. The numerical procedure was validated by a 3-dimensional gas flow in the annular channel. Applying the validated model, the flow character- istics of TiCl4 in the oxidation reactor with a tangential inlet were simulated and characterized. The flow distribu- tion with five rectifying rings of different structure was simulated and analyzed. The results showed that the rectifying ring improved the distribution uniformity of the pressure and outlet velocity. Compared to the original case without a rectifying ring, the non-uniformity of the pressure and outlet velocity could be reduced by up to 91% and 69% respectively. The rectifying ring #5, which can be installed and adjusted easily, is more effective in realizing even distribution. In addition, installation of the rectifying ring effectively reduced the circulating flow in an annular channel as well as the total energy loss.

A novel method for improving cerussite sulfidization

Evaluation of flotation behavior, solution measurements, and surface analyses were performed to investigate the effects of chloride ion addition on the sulfidization of cerussite in this study. Micro-flotation tests indicate that the addition of chloride ions prior to sulfidization can significantly increase the flotation recovery of cerussite, which is attributed to the formation of more lead sulfide species on the mineral surface. Solution measurement results suggest that the addition of chloride ions prior to sulfidization induces the transformation of more sulfide ions from pulp solution onto the mineral surface by the formation of more lead sulfide species. X-ray diffraction and energy-dispersive spectroscopy indicate that more lead sulfide species form on the mineral surface when chloride ions are added prior to sulfidization. These results demonstrate that the addition of chloride ions prior to sulfidization can significantly improve the sulfidization of cerussite, thereby enhancing the flotation performance.

An Industrial Perspective on Magnesium Alloy Wheels: A Process and Material Design

Light weights wheels improve vehicle performance with respect to road handling, cornering as well providing fuel economy and reduced greenhouse gas emissions. Aluminum wheels are currently used in many models and are produced usually by low pressure assisted gravity casting. Important property requirements are fatigue strength, pressure tightness, tensile strength, impact resistance, and corrosion resistance. Many attempts have been made to convert aluminum road wheels to magnesium. Race cars and some of the high end models (Porsche, Ferrari, etc.) have used magnesium wheels. These wheels have been gravity cast or forged. Viable corrosion protection systems have been developed and magnesium wheels have been used with success on these models. To use magnesium on more modest models is a challenge due to cost issues. Higher productivity casting processes or more cost effective coating systems need to be utilized. The project consists of selecting magnesium alloys for road wheels, examining the possible cost effective casting processes and corrosion protection systems, evaluating the cost per one wheel and comparing it to aluminum wheel costs. The wheels will also be compared with respect to fatigue and impact properties, pressure tightness, and corrosion.

Ternary PtSmCo NPs electrocatalysts with enhanced oxygen reduction reaction

PtSmCo ternary metal nanoparticles(NPs)were synthesized as electrocatalysts for oxygen reduction reaction(ORR).Firstly,SmCo NPs were prepared by potentiostatic electrodeposition in ionic liquids(ILs),and the average particle diameter of SmCo NPs corresponds to about 238 nm(-0.65 V),72 nm(-0.75 V)and 45 nm(-0.85 V),respectively.Secondly,displacement and reductions of SmCo NPs occur in the K2 PtCl4 and L-ascorbic acid sodium with about 3 nm of Pt NPs which grow on the surface of SmCo NPs to form PtSmCo ternary metal NPs.Studies of cycle voltammetry(CV)and line sweep voltammetry(LSV)indicate that the electrocatalytic property for ORR generates a decreasing order of commercial Pt/C>PtSmCo0.85>PtSmCo0.75>PtSmCo0.65.Accelerated durability testing(ADT)after 10000 cycles shows that PtSmCo0.85 NPs electrocatalyst decreases by-40%in electrochemical active surface areas(ECSA),the half-wave potential(E1/2)only negatively shifts by 14 mV and decreases by^13.6%in mass activity(MA).When compared with JM Pt/C,where it decreases by^49%in ECSA,E1/2 is negatively shifted by 40 mV and decreased by^50%in MA.Therefore,PtSmCo0.85 NPs electrocatalyst is more stable than JM Pt/C.

Stabilization/solidification mechanisms of tin tailings and fuming slag-based geopolymers for different heavy metals

Tin mine tailings(TMT)and fuming slag(FS)contain many heavy metals(As,Cr,Cu,Zn and Mn)that cause severe pollution to the environment.Herein,geopolymers were prepared using TMT,FS and flue gas desulfurization gypsum(FGDG)to immobilize heavy metals,and their compressive strength and heavy metal leaching toxicity were investigated.It was first determined that T4F5(TMT:FS=4:5)sample exhibited the highest compressive strength(7.83 MPa).T4F5 achieved 95%immobilization efficiency for As and Cr,and nearly 100%for Cu,Zn and Mn,showing good immobilization performance.A series of characterization analyses showed that heavy metal cations can balance the charge in the geopolymer and replace Al in the geopolymer structure to form covalent bonds.In addition,about 2%–20%of heavy metal Fe was immobilized in hydration products,heavy metal hydroxides and non-bridging Si–O and Al–O coordination with silica-aluminate matrices.AsO_(3)^(3−) was oxidized into AsO_(4)^(3−),which may form Ca–As or Fe–As precipitates.Cr_(2)O_(7)^(2−)was converted to CrO_(4)^(2−)under alkaline environment and then combined with OH−to form Cr(OH)3 precipitates.Mn^(2+)may react directly with dissolved silicate to form Mn_(2)SiO_(4) and also form Mn(OH)_(2) precipitates.The unstable Mn(OH)_(2) can be further oxidized to MnO_(2).The heavy metal cations were immobilized in the silicoaluminate lattice,while the anions tended to form insoluble precipitates.These results may benefit the industry and government for better handling of TMT,FS and solid wastes containing the abovementioned five heavy metals.

Synthesis of three-dimensionally ordered porous perovskite type LaMnO_3 for Al-air battery

LaMnO3 catalysts with three-dimensionally ordered holes perovskite structure were prepared via closepacked SiO2 template synthesized by Stober-Frink method. SEM, XRD and BET were employed to characterize the microstructure, phases and specific surface area. CV method was used to the oxygen electrode beha-vior of catalysts. Diameter of the holes was about 330 nm, corresponding to the size of SiO2 template. Full-cell discharge tests were performed on aluminum-air battery fabricated by porous LaMnO3.Results showed that the discharge performance of porous LaMnO3 were 1.54 V, 1.42 V and 1.24 V respectively when the discharge currents were set at 5 mA/cm^2,10 mA/cm^2 and 20 mA/cm^2, respectively, which were higher than that of LaMnO3 prepared by coprecipitation method（1.33 V, 1.09 V, 0.63 V, respectively）.