Effects of annealing treatment on microstructure and tensile behavior of the Mg-Zn-Y-Nd alloy

In the present study,the Mg-4Zn-0.6Y-0.5Nd alloy was hot extruded and annealed at 200℃,225℃ and 250℃ for different time to optimize microstructure and mechanical properties.The results exhibit that the dual-size grain structure and linearly distributed secondary phase are the main feature of the as-extruded Mg-Zn-Y-Nd alloy,which can be described as the elongated grain is surrounded by the fine equiaxed grain.Moreover,the as-extruded alloy shows strong{011^(-)0}fiber texture feature,especially for the large elongated grains.The annealing treatment results in static recrystallization,which increases fine equiaxed grains but decreases large elongated grains.In addition,the equiaxed grains formed during the annealing treatment demonstrate relative random orientations,which weaken the{011^(-)0}fiber texture of the alloy.Moreover,during the annealing at 225℃and 250℃,the extension twins begin to form in the alloy and weaken the{011^(-)0}fiber texture of the alloy further.The annealing treatment has little influence on the linearly distributed secondary phase but promotes the coarsening of small precipitates at 250℃.The annealing treatment could increase the yield and ultimate strength,but the elongation decreases,especially at higher temperature.Such a variation can be ascribed to the evolution of texture,grain structure,twinning and precipitation during the annealing treatment.

Effect of annealing treatment on microstructures and properties of austenite-based Fe-28Mn-9Al-0.8C lightweight steel with addition of Cu

The mechanical properties of an austenite-based Fe-Mn-Al-C lightweight steel were improved by co-precipitation of nanoscale Cu-rich and κ-carbide particles.The Fe-28Mn-9Al-0.8C-(0,3)Cu (wt.%) strips were near-rapidly solidified and annealed in the temperature range from 500 ℃ to 700 ℃.The microstructure evolution and mechanical properties of the steel under different annealing processes were studied.Microstructural analysis reveals that nanoscale κ-carbides and Cu-rich particles precipitate in the austenite and ferrite of the steel in this annealing temperature range.Co-precipitation of nanoscale Cu-rich particles and κ-carbides provides an obvious increment in the yield strength.At the annealing temperature of 600 ℃,both the yield strength and ultimate tensile strength of Fe-28Mn-9Al-0.8C-3Cu (wt.%) steel strip are the highest.The total elongation is 25%,which is obviously higher than that of Cu-free steel strips,for the addition of Cu reduces the large sized κ-carbides precipitated along austenite/ferrite interfaces.When the annealing temperature rises to 700 ℃,the strength and ductility of the two steel strips deteriorate due to the formation of massive intergranular κ-carbides precipitated along austenite/ferrite interfaces.It can be concluded that a proper co-precipitation of Cu-rich particles and κ-carbides would improve the properties of austenite-based Fe-Mn-Al-C steel.

The effect of annealing treatment on the microstructures and mechanical properties of cold-sprayed nickel coating

The effect of annealing treatment on the microstructures and mechanical properties of cold-sprayed Ni coating was investigated by conducting micro-hardness and tensile tests and using a normal optical microscope （OM） ,a scanning electron microscope （ SEM）, a transmission electron microscope （TEM） and an electron probe X-ray microanalyzer （EPMA）. The results show that following the increase of the annealing temperature ,the micro-hardness of cold-sprayed Ni coating decreases and the elongation after fracture increases, while the tensile strength increases before decreasing. The tensile deformation and fracture behavior change from a typical brittle fracture to a hybrid brittle and ductile fracture, then to a typical ductile failure. It is found that when annealed at an elevated temperature （ e. g. 900℃ ） ,the grains tend to grow abnormally with the oxides spheroidizing and the defects agglomerating at the interfaces, causing the tensile strength reduction of the cold-sprayed nickel coating. It is also pointed out that the tensile strength of the cold-sprayed Ni coating can be significantly improved by the appropriate annealing procedures, but the elongation after fracture cannot be clearly increased because it is difficult to eliminate the main defects in the coating by the following heat treatments.

Impact of Annealing Treatment on the Behaviour of Titanium Dioxide Nanotube Layers

In this work, we study the influence of the annealing treatment on the behaviour of titanium dioxide nanotube layers. The heat treatment protocol is actually the key parameter to induce stable oxide layers and needs to be better understood. Nanotube layers were prepared by electrochemical anodization of Ti foil in 0.4 wt% hydrofluoric acid solution during 20 minutes and then annealed in air atmosphere. In-situ X-ray diffraction analysis, coupled with thermogravimetry, gives us an inside on the oxidation behaviour of titanium dioxide nanotube layers compared to bulk reference samples. Structural studies were performed at 700°C for 12 h in order to follow the time consequences on the oxidation of the material, in sufficient stability conditions. In-situ XRD brought to light that the amorphous oxide layer induced by anodization is responsible for the simultaneous growths of anatase and rutile phase during the first 30 minutes of annealing while the bulk sample oxidation leads to the nucleation of a small amount of anatase TiO2. The initial amorphous oxide layer created by anodization is also responsible for the delay in crystallization compared to the bulk sample. Thermogravimetric analysis exhibits parabolic shape of the mass gain for both anodized and bulk sample;this kinetics is caused by the formation of a rutile external protective layer, as depicted by the associated in-situ XRD diffractograms. We recorded that titanium dioxide nanotube layers exhibit a lower mean mass gain than the bulk, because of the presence of an initial amorphous oxide layer on anodized samples. In-situ XRD results also provide accurate information concerning the sub-layers behavior during the annealing treatment for the bulk and nanostructured layer. Anatase crystallites are mainly localized at the interface oxide layer-metal and the rutile is at the external interface. Sample surface topography was characterized using scanning electron microscopy (SEM). As a probe of the photoactivity of the annealed TiO2 nanotube layers, degradation of an acid orange 7 (AO7) dye solution and 4-chlorophenol under UV irradiation (at 365 nm) were performed. Such titanium dioxide nanotube layers show an efficient photocatalytic activity and the analytical results confirm the degradation mechanism of the 4-chlorophenol reported elsewhere.

Effect of Cu doping and annealing treatment on the microstructure and mag-netic properties of nanocrystalline single-phase Nd-Fe-B alloys

The effects of Cu addition and annealing treatment on the magnetic properties and microstructure of Ndl2.3Fe81.7-xCuxB6 （x=0-1.2） ribbons melt-spun and annealed were systematically investigated by the methods of vibrating sample magnetometer （VSM）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. Optimum magnetic properties were achieved by annealing melt-spun Nd12.3Fe81.5Cu0.2B6 ribbons at 550℃ for 15 min, which only contained Nd2Fe14B phase. The remanence, coercive force, and maximum energy product increase by 18.4%, 36.2%, and 49% respectively compared with those of Cu-free samples. The sig- nificant improvement in magnetic properties originates from the freer grains of the samples by introducing Cu, which leads to the stronger exchange-coupling between neighboring grains.

Insight into the structural transformation of tetraphenylethylene acids at liquid–solid interface induced by linear aminofunctionalized triazine derivatives and annealing treatment

The interaction between organic photoelectric molecules leads to the formation of a certain aggregation structure,which plays a pivotal role in the charge transport at the intermolecular interface.In view of this,we investigated the mechanism and law of intermolecular interaction by detecting the self-assembled behaviors between organic photoelectric molecules at the interface by scanning tunneling microscopy(STM).In this work,the structural transformations of tetraphenylethylene acids(H_(4)ETTCs)on graphite surface induced by temperature and triazine derivatives(zcy-19,zcy-27,and zcy-38 molecules)were studied by STM technology and density functional theory(DFT)calculations.At room temperature,zcy-19 and H_(4)ETTC molecules formed a small range of ordered co-assembled nanostructure,while for zcy-27 or zcy-38 molecules,no co-assembled nanostructures were observed and only their own self-assembled structures existed on graphite surface,individually.In the thermal annealing trials,the original co-assembled H_(4)ETTC/zcy-19 structure disappeared,and only zcy-19 and H_(4)ETTC self-assembled in separate domains.Nevertheless,new well-ordered H_(4)ETTC/zcy-27 or H_(4)ETTC/zcy-38 co-assembled structures appeared at different annealing temperatures,respectively.Combined with DFT calculations,we further analyzed the mechanism of such structural transformations by triazine derivatives and temperature.Results reveal that triazine derivatives could interact with H_(4)ETTC by N–H···O and O–H···N hydrogen bondings,and whether temperature or zcy series compounds could achieve successful regulation of H_(4)ETTC assembly behavior is closely associated with the conjugated skeleton length of zcy series compounds.

Effect of annealing treatment on microstructures,mechanical properties and cavitation erosion performance of high velocity oxy-fuel sprayed NiCoCrAlYTa coating

The mechanical parts serving in the marine environment are up against the dual damage of corrosion and cavitation erosion,so the Ni Co Cr Al YTa coating with excellent corrosion resistance is successfully prepared by high velocity oxy-fuel(HVOF)sprayed technology to protect the equipment from deterioration.The chemical composition and mechanical properties as well as the microstructure evolution of the coating before and after annealing treatment are studied.At the same time,the influence of annealing treatment on the corrosion and cavitation erosion behaviors of the coating is investigated,as well.The NiCoCrAlYTa coating mainly containsγ-Ni,β-Ni Al,andγ’-Ni3Al phases.During the deposition,the microcrystals or incomplete crystals generate in the interior of the coating because of the large temperature difference and impact force.Meanwhile,there is twin crystal structure in the as-spayed coating.After annealing treatment,the growth of grains and the segregation of reactive elements improve interface strength and inhibit the formation of micro-defects in the coating.The annealing temperature is of significance to the microstructure,mechanical properties,anti-corrosion and cavitation erosion resistance of the coating.This study provides a combined approach toward improving the corrosion and cavitation erosion resistance of NiCoCrAlYTa coatings.

Influence of annealing treatment on microstructure and properties of cold sprayed stainless steel coatings

304 stainless steel coatings had been deposited on carbon-steel substrate by cold spray technique, vacuum annealing treatment was applied to the coatings with different temperatures, and the influence of annealing treatment on the microstructure and electrochemical behavior of the coatings in 3.5% NaCl were analyzed. The results indicated that, the cold sprayed coating was constituted by the flattened particles, and the interfaces were clearly observed between the deposited particles. It was also found that annealing treatment led to the recovery and recrystallization of the elongated grains in the as-sprayed coatings with the increase of annealing temperature. When the annealing temperature achieved to 950 ？ C, the interface of particles was disappeared and the coating s structure was made of new recrystallization austenite grains. Annealing treatment increased the potential volts, and reduced the corrosion rate with the increase of annealing temperature. The electrical corrosion morphology indicated that, the corrosion was firstly at the distortion area and the crevice corrosion mechanism played an important part. Based on these results, processes active during annealing treatment are kinetically dependent and strongly influenced by the annealing treatment temperature.

Residual-stress relaxation mechanism and model description of 5052H32 Al alloy spun ellipsoidal heads during annealing treatment

Marginal-restraint mandrel-free spinning is an advanced technology for manufacturing ellipsoidal heads with large diameter-thickness ratios.Nevertheless,the spinning-induced residual stress,which greatly influences the in-service performance of spun heads,should be removed.In this study,the effects of annealing on the residual-stress relaxation behavior of 5052H32 aluminum alloy spun heads were investigated.It is found that the residual stress first rapidly decreases and then remains steady with the increase in annealing time at the tested annealing temperatures.The relaxation of the residual stress becomes increasingly obvious with the increase in annealing temperature.When the annealing temperature is less than 220℃,there are no obvious changes in grain size.Moreover,the spinning-induced dislocations are consumed by the static recovery behavior,which decreases the residual stress during annealing.When the annealing temperature is approximately 300℃,the broken grains transform into equiaxed grains.In addition,static recrystallization and recovery behaviors occur simultaneously to promote the relaxation of the residual stress.Considering the different stress relaxation mechanisms,a model based on the Zener-Wert-Avrami equation was established to predict the residual-stress relaxation behavior.Finally,the optimized annealing temperature and time were approximately 300C and 30 min,respectively.

Influence of post-grown treatments on CuInS_2 thin films prepared by sulphurization of Cu-In films

Polycrystalline CuInS2 （CIS） films were prepared by sulphurization of Cu-In films. The surface morphology and phase composition of the as-grown film, the KCN-etched film, and the annealed KCN-etched film were investigated. During the sulphurization, the secondary CuxS phase segregated on the surface of the as-grown films. To improve the crystalline quality of CuInS2 films, a series of post-grown treatments, such as KCN-etching and vacuum annealing KCN-etched films, were performed on the as-grown films. Both as-grown and post-treated films were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and energy dispersive spectroscopy （EDS）. The results indicated that a CuxS secondary phase segregated on the surface of the as-grown film, which could be removed effectively by KCN etching. After the vacuum annealing treatment, the KCN-etched film had a sphalerite structure with （112） preferred orientation. Meanwhile, the crystalline quality of the CIS film was significantly improved, which provided a novel method to improve the performance of thin film solar cells.

ANNEALING INDUCED VARIATION OF CRYSTALLINE STRUCTURE AND MECHANICAL PROPERTIES OF SYNDIOTACTIC POLYPROPYLENE FIBERS

Syndiotactic polypropylene （sPP） as-spun fiber （sPP1） and drawn fiber （sPP2） were prepared by melt-spinning and melt-spinning/hot-drawing, respectively. The structure transition of the two fibers induced by annealing at different temperatures and the corresponding mechanical properties were subsequently investigated by the combination of Fourier transform infrared spectroscopy （FTIR）, wide-angle X-ray diffraction （WAXD） and tensile testing. The results indicate that the chain conformation and crystal forms of the two sPP fibers are not obviously changed at low annealing temperature （40℃）. With increasing the annealing temperature, the trans-planar conformation and mesophase in sPP1 and sPP2 fibers can be completely transformed to helical conformation and crystal form I under tension. Upon removing the tension, a small amount of mesophase and trans-planar conformation will be regained. The mechanical properties of the annealed fibers are manifestly dependent on their initial structure and the annealing temperature.

Effect of annealing on properties of Al/steel composite plates prepared by surface oxidation treatment before cold roll bonding

Al/steel composite plate has a wide application prospect,but great differences in properties between Al and steel are observed.It is difficult to obtain high bonding strength by the traditional cold roll bonding process.Al/steel composite plate was thus prepared by cold roll bonding at a reduction rate of 60%after oxidation treatment on the surface to be composited on the steel side.The heat treatment of holding at 400℃ for 1 h and cooling with the furnace was then adopted.The bonding strength,microstructure,and properties of the Al/steel composite plate before and after annealing were analysed and compared through shear test,bending test,tensile test,and micro-characterization.Results show that the shear strengths of the interface before and after annealing are 100 and 80 MPa,respectively.Although the shear strength of the annealed Al/steel composite plate decreases,the bending and overall tensile properties of the composite plate are improved,showing better mechanical properties.

Delayed Fracture Behavior of CrMo Type High Strength Steel Containing Vanadium

The netlike eutectic carbide in twin roll casting strip of W9Cr4V2 was dissolved and broken up gradually with increasing heating temperature during annealing treatment. Almost all eutectic carbides exist in granular form with heating temperature up to 950 ℃. It is considered that the refining of lamellar spacing made it possible for eutectic carbide to be granulated.

Morphological Variation of Eutectic Carbide in Twin-Roll Casting Strip of W9Cr4Mo2

The netlike eutectic carbide in twin-roll casting strip of W9Cr4V2 was dissolved and broken up gradually with increasing heating temperature during annealing treatment.Almost all eutectic carbides exist in granular form with heating temperature up to 950 ℃.It is considered that the refining of lamellar spacing made it possible for eutectic carbide to be granulated.

Cementites decomposition of a pearlitic ductile cast iron during graphitization annealing heat treatment

Cementites decomposition of a pearlitic ductile cast iron during graphitization annealing heat treatment was investigated.Fractographies and microstructures of heat treated samples were observed using a scanning electron microscope and mechanical properties were measured by a universal tensile test machine.The results indicated that during isothermal annealing at 750°C,the tensile strength of pearlitic ductile cast iron was increased to a peak value at 0.5h,and decreased gradually thereafter but the elongation was enhanced with the increase of annealing time.Moreover,the diffusion coefficient of carbon atoms could be approximately calculated as 0.56μm2/s that could be regarded as the shortrange diffusion.As the holding time was short（0.5h）,diffusion of carbon atoms was incomplete and mainly occurred around the graphites where the morphology of cementites changed from fragmentized shape to granular shape.In addition,the ductile cast iron with tensile strength of 740MPa and elongation of 7% could be achieved after graphitization annealing heat treatment for 0.5h.Two principal factors should be taken into account.First,the decomposition of a small amount of cementites was beneficial for increasing the ductility up to elongation of 7%.Second,the diffusion of carbon atoms from cementites to graphites could improve the binding force between graphites and matrix,enhancing the tensile strength to 740 MPa.

Stability of Retained Austenite Through a Combined Intercritical Annealing and Quenching and Partitioning(IAQP) Treatment

Intercritical annealing（IA） at various temperatures followed by quenching and partitioning（IAQP） treatments was conducted on a cold-rolled Fe-0.2C-1.42Si-l.87Mn（wt%） sheet steel.Optimized microstructure and enhanced mechanical properties were achieved through appropriate adjustment of IA temperatures.The steel which was annealed at1,033 K for 600 s,then quenched to 573 K and partitioned at 693 K for 20 min,designated as 1033 QP steel,exhibits maximum 16.3 vol% retained austenite（RA） with good mechanical properties（ultimate tensile strength 886 MPa and total elongation 27%）.It was found that the thermal and mechanical stabilities of RA are mainly influenced by the combined effect of its average carbon content and amount of adjacent martensite.Furthermore,the transformation-induced plasticity effect increased the peak n-values observed at the second stage of the work hardening of IAQP steels.

Heat treatment enhancing the compressive fatigue properties of open-cellular Ti-6Al-4V alloy prototypes fabricated by electron beam melting

In this work, we report the effect of annealing in α＋β phase field on the fatigue properties of Ti-6A1-4V alloy meshes fabricated by electron beam melting. The results show that annealing at high temperature near the phase boundary enhances the ductility of the brittle mesh struts due to the formation of coarse α lamellas with a large thickness/length ratio. Accordingly, the fatigue endurance ratio of the studied meshes increases to up to -0.6, which is much superior to that of the as-fabricated counterparts and comparable to those of dense materials.2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.

Influence of Annealing Temperature on the Microstructure and Electrical Properties of Indium Tin Oxide Thin Films

Indium tin oxide （ITO） thin films were prepared on alumina ceramic substrates by radio frequency magnetron sputtering. The samples were subsequently annealed in air at temperatures ranging from 500 to 1,100 ℃ for 1 h. The influences of the annealing temperature on the microstructure and electrical properties of the ITO thin films were investigated, and the results indicate that the as-deposited ITO thin films are amorphous in nature. All samples were crystallized by annealing at 500 ~C. As the annealing temperature increases, the predominant orientation shifts from （222） to （400）. The carrier concentration decreases initially and then increases when the annealing temperature rises beyond 1,000 ℃. The resistivity of the ITO thin films increases smoothly as the annealing temperature increases to just below 900 ℃. Beyond 900 ℃, however, the resistivity of the films increases sharply. The annealing temperature has a significant effect on the stability of the ITO/Pt thin film thermocouples （TFTCs）. TFTCs annealed at 1,000 ℃ show improved high- temperature stability and Seebeck coefficients of up to 77.73 pV/℃.

Effect of Solution Annealing Temperature on Pitting Behavior of Duplex Stainless Steel 2204 in Chloride Solutions

The effect of solution annealing temperature ranging from 950 to 1 200 ℃ on the microstructure and corrosion performance of duplex stainless steel （DSS） 2204 were investigated. The proportion of the ferrite phase increased while the austenite phase decreased and the ferrite stabilizing elements diluted in the ferrite phase with the increase of annealing temperature. The critical pitting temperature （CPT） of specimens annealed at 1000℃ was higher than those annealed at 950℃, whereas further increasing the annealing temperature to 1200℃ decreased the CPT. The pitting initiation sites were observed in the austenite phase, at the boundary of ferrite/austenite phase and inside the ferrite phase for specimens annealed at 950, 1000℃ and exceeding 1 100℃, respectively. The evolution trend of the CPT and the pit initiation site were analyzed by the pitting resistance equivalent number.

Hydrogen storage properties of as-cast and annealed low-Co La1.8Ti0.2MgNi8.9Co0.1 alloys

Low-Co Lal.8Ti0.2MgNi8.9Co0.1 alloys were prepared by magnetic levitation melting followed by annealing treatment. The effect of annealing on the hydrogen storage properties of the alloys was investigated systematically by X-ray diffraction （XRD）, pressure-com- position isotherm （PCI）, and electrochemical measure- ments. The results show that all samples contain LaNi5 and LaMg2Ni9 phases. LaCo5 phase appears at 1,000 ℃. The enthalpy change of all hydrides is close to -30.6 kJ.mo1-1 H2 of LaNi5 compound. Annealing not only increases hydrogen capacity and improves cycling stability but also decreases plateau pressure at 800 and 900 ℃. After annealing, the contraction of cell volume and the increase of hydride stability cause the high rate dischargeability to reduce slightly. The optimum alloy is found to be one annealed at 900 ℃, with its hydrogen capacity reaching up to 1.53 wt%, and discharge capacity remaining 225.1 mAh·g-1 after 140 charge-discharge cycles.