EFFECT OF CRYOGENIC AND HEATING TREATMENT ON THE SOLUTION PROPERTIES OF NITROCELLULOSE

The effect of cryogenic and heating treatment on the solution properties of rigid polymer nitrocellulose(NC)indilute tetrahydrofuran solution were studied with a sealed viscometer and a size exclusion chromatograph(SEC),respectively.The experimental results show that the relative viscosity of NC solution decreases after repeated freezing-thawing treatment.The decreased viscosity value of NC could not be restored but decreased further after the solution beingre-heated.The experimental results of SEC are fully consistent with that of viscosity measurements.It is believed that theeffect of two treatments on NC solution both causes the apparent hydrodynamic volume to decrease.But they are assumed tobe ascribed to different mechanisms.

Effect of heating treatment on trap level distribution in polyamide 66 film electrets

The effect of heating treatment on the trap level distribution in polyamide 66 film electret is studied by thermally stimulated depolarization current （TSDC） technique. For annealed polyamide 66, there are three trap levels that respectively originate from space charge trapped in amorphous phase, interphase and crystalline phase. There is one peak that originates from space charge trapped in amorphous phase for quenched one. Using multi-point method to fit the experimental curves, the detrapping current peaks can be separated and the trap depth is obtained. The shallower trap levels trapped in amorphous phase and interphase are obviously close to the deeper trap level trapped in crystalline phase for annealed polyamide 66 as the polarization temperature increases, while the trap level distribution remains unaffected by polarization temperature for quenched one.

Interface property of dissimilar Ti-6Al-4V/AA1050 composite laminate made by non-equal channel lateral co-extrusion and heat treatment

The purpose of this paper is to examine the effect of processing parameters and subsequent heat treatments on the microstructures and bonding strengths of Ti-6Al-4V/AA1050 laminations formed via a non-equal channel lateral co-extrusion process.The microstructural evolution and growth mechanism in the diffusion layer were discussed further to optimize the bonding quality by appropriately adjusting process parameters.Scanning electron microscopes(SEM),energy dispersive spectrometer(EDS),and X-ray diffraction(XRD)were used to characterize interfacial diffusion layers.The shear test was used to determine the mechanical properties of the interfacial diffusion layer.The experimental results indicate that it is possible to co-extrusion Ti-6Al-4V/AA1050 compound profiles using non-equal channel lateral co-extrusion.Different heat treatment processes affect the thickness of the diffusion layer.When the temperature and time of heat treatment increase,the thickness of the reaction layers increases dramatically.Additionally,the shear strength of the Ti-6Al-4V/AA1050 composite interface is proportional to the diffusion layer thickness.It is observed that a medium interface thickness results in superior mechanical performance when compared to neither a greater nor a lesser interface thickness.Microstructural characterization of all heat treatments reveals that the only intermetallic compound observed in the diffusion layers is TiAl_(3).Due to the inter-diffusion of Ti and Al atoms,the TiAl_(3) layer grows primarily at AA1050/TiAl_(3) interfaces.

Effect of Heat Treatment on Microstructure and Mechanical Properties of Multiscale SiC_p Hybrid Reinforced 6061 Aluminum Matrix Composites

The performance of solid solution aging treatment on aluminum matrix composites prepared by powder metallurgy and reinforced with 6061 aluminum alloy powder as matrix;meanwhile, nano silicon carbide particles(nm Si Cp), submicron silicon carbide particles(1 μm Si Cp) and Ti particles were studied. The Al/Si Cp composite powder was prepared by high-energy ball milling, and then cold-pressed, sintered, hotextruded, and then heat-treated with different solution temperatures and aging times for the extruded composites. Optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy(EDS), X-ray diffractometer(XRD) and extrusion testing were used to analyze and test the microstructure and mechanical properties of aluminum matrix composites. The results show that after the multi-stage solid solution at 530 ℃×2 h+535 ℃×2 h+540 ℃×2 h, the particles are mainly equiaxed grains and uniformly distributed. There is no reinforcement agglomeration, and the surface is dense and the insoluble phase is basically dissolved. In the matrix, the strengthening effect is good, and the hardness and compressive strength are 179.43 HV and 680.42 MPa, respectively. Under this solution process, when the aluminum matrix composites are aged at 170 ℃ for 10 h, the hardness and compressive strength can reach their peaks and increase to 195.82 HV and 721.48 MPa, respectively.

Influence of heat treatment on microstructure,mechanical and corrosion behavior of WE43 alloy fabricated by laser-beam powder bed fusion

Magnesium(Mg)alloys are considered to be a new generation of revolutionary medical metals.Laser-beam powder bed fusion(PBF-LB)is suitable for fabricating metal implants withpersonalized and complicated structures.However,the as-built part usually exhibits undesirable microstructure and unsatisfactory performance.In this work,WE43 parts were firstly fabricated by PBF-LB and then subjected to heat treatment.Although a high densification rate of 99.91%was achieved using suitable processes,the as-built parts exhibited anisotropic and layeredmicrostructure with heterogeneously precipitated Nd-rich intermetallic.After heat treatment,fine and nano-scaled Mg24Y5particles were precipitated.Meanwhile,theα-Mg grainsunderwent recrystallization and turned coarsened slightly,which effectively weakened thetexture intensity and reduced the anisotropy.As a consequence,the yield strength and ultimate tensile strength were significantly improved to(250.2±3.5)MPa and(312±3.7)MPa,respectively,while the elongation was still maintained at a high level of 15.2%.Furthermore,the homogenized microstructure reduced the tendency of localized corrosion and favoredthe development of uniform passivation film.Thus,the degradation rate of WE43 parts was decreased by an order of magnitude.Besides,in-vitro cell experiments proved their favorable biocompatibility.

Discussion on the Free Quenching Heat Treatment Process of Automotive Leaf Springs

Free quenching of automotive leaf springs is a new technology that has gradually started to be applied in the industry in China in recent years.Only a few manufacturers are applying it in the industry.Through more than half a year of on-site practice,the changes in the hot forming of spring plates before free quenching have been explored,and finally a heat treatment process that meets the production requirements of our company has been developed,achieving normal production.

Formation of fine fully-lamellar microstructure of TiAl-based alloy in rapid heating cyclic heat treatment process

The optical observation results of neocrystallization nucleation and growth of fine fully lamellar (FFL) α 2/ γ microstructure of a TiAl based alloy in rapid heating cyclic heat treatment process were reported. The characteristics of α+γ→α transformation under rapid heating conditions were analysed. A model for explaining the nucleation and growth mechanism of FFL α 2/ γ microstructure was proposed.

Effect of heat treatment on the microstructure and mechanical properties of a multidirectionally forged Mg-Gd-Y-Zn-Zr-Ag alloy

Multidirectional forging(MDF)was successfully applied to fabricate large-size Mg-Gd-Y-Zn-Zr-Ag alloy in this work and effects of T4,T5 and T6 treatments on the microstructure and mechanical properties of the as-forged alloy were analyzed.Results show that dynamic recrystallization(DRX)occurs and second phase particles precipitate along the grain boundary during the MDF process.After annealing treatment(T4),the volume fraction and size of dynamic precipitates slightly increase at a lower temperature(430℃)compared with those of MDFed sample,while they are dissolved into theα-Mg matrix at a higher temperature(450℃).At the meantime,short plate-shaped long-period stacking ordered(LPSO)phases are observed in the DRX grains of the MDFed sample and then dissolved into theα-Mg matrix during annealing at both temperatures.Typical basal texture is identified in the MDFed sample,but the basal pole tilts away from final forging direction and rare-earth texture component with<1121>orientation parallel to penultimate forging direction becomes visible after annealing.The T6 sample annealing at 430℃for 4 h and ageing at 200℃for 34 h exhibits the superior strength and ductility in this study.The ultimate tensile strength,tensile yield strength and elongation to failure,which is 455 MPa,308 MPa and 7.7%,respectively,are overall improved compared with the directly-aged(T5)sample.This paper provides a superior heat treatment schedule to manufacture high-performance large-scale Mg-Gd-Y-Zn-Zr-Ag components for industrial production.

Effect of heat treatment on microstructure,mechanical and tribological properties of in-situ (TiC+TiB)/TC4 composites by casting

To enhance the performance of in-situ synthesized 6vol.%(Ti C+Ti B)/TC4 titanium matrix composites fabricated by casting,a variety of heat treatment processes were carried out.Upon conducting microstructure observations following various heat treatments,it was found that the composites exhibit a basketweave microstructure,consisting of an α phase and a transformed β phase.The sizes of(α+β) phases were found to be refined to varying degrees after the heat treatment processes,while the morphology of Ti B remains largely unchanged and Ti C becomes granulated.Compressive testing revealed that all composites subjected to different heat treatments demonstrate a notable increase in ultimate compressive strength as well as a slight improvement in plasticity compared to the as-cast state.The results of the tribological performance test indicated that the heat-treated composites exhibit lower average friction coefficient,specific wear rate,and worn surface roughness compared to the as-cast composite.Among the heat treatment processes studied,the composite solution heated at 1,150 °C/1 h followed by air cooling,then 950 °C/1 h followed by air cooling,and finally 500 °C/4 h followed by air cooling,demonstrates the highest levels of hardness,compressive strength,and wear resistance.These improvements are attributed to the combined effects of solid solution strengthening,grain refinement,and the pinning of dislocation slip.

Insights into the relations between cell wall integrity and in vitro digestion properties of granular starches in pulse cotyledon cells after dry heat treatment

Natural foods,such as whole pulses,are recommended in the dietary guidelines of the US and China.The plant cell wall structure in whole pulses has important implications for the nutritional functionalities of starch.In this study,garbanzo bean cells with varying degrees of cell wall integrity were subjected to dry heat treatment(DHT)and used to elucidate the food structure-starch digestion properties of pulse food.The morphological features suggested that all cell samples do not exhibit remarkable changes after being subjected to DHT.Molecular rearrangement and the crystallite disruption of starch granules entrapped in cells occurred during DHT as assessed by the crystal structure and thermal properties.DHT decreased the inhibitory effects of enzymes of both the soluble and insoluble components,but the digestion rate and extent of slightly and highly damaged cell samples did not exhibit significant differences compared with their native counterparts.We concluded that the starch digestion of pulse cotyledon cells is primarily determined by the intactness of the cellular structure.This study reveals the role of food structure on the ability to retain the desirable nutritional properties of starch after subjection to physical modification.

Improving corrosive wear resistance of Mg-Zn-Y-Zr alloys through heat treatment

The wear behavior of an as-received Mg-Zn-Y-Zr alloy before and after a facile heat treatment was investigated under sliding in air and 0.5 wt.%NaCl solution.Results revealed that the wear resistance of the alloy was remarkably enhanced after the heat treatment,irrespective of testing condition.The wear mechanism was predominantly abrasive wear accompanied by oxidation under the dry sliding condition,while corrosive wear was dominant under sliding in the NaCl solution.The superior corrosive wear resistance was attributed to the homogenous distribution of fine I-phase precipitates in the alloy by the heat treatment,leading to a reduction in wear,corrosion as well as wear-corrosion synergy.The wear-accelerated corrosion rate was remarkably alleviated after the heat treatment.

Effect of Solution-ECAP-Aging Treatment on the Microstructure and Properties of TB8 Titanium Alloy

The microstructure and mechanical properties of the TB8 titanium alloy were controlled by a secondary processing technology of solution-equal channel angular pressing(ECAP)-aging treatment,which combined strong plastic deformation with heat treatment. The effects of ECAP and heat treatment on the microstructure and properties of the titanium alloy were systematically investigated by optical microscopy(OM), scanning electron microscopy(SEM), hardness tests, and tensile property analysis. The results indicate that the metallographic structure without ECAP treatment is mainly equiaxed β-phase, while that after ECAP treatment is equiaxed β-phase with grain fragmentation, slip bands, and new small grains. After 850 ℃ solutionECAP-520 ℃ aging treatment, the titanium alloy has the smallest grain size, while the directionality of tissue growth along the ECAP direction is the most apparent. Under the same solution-aging conditions, the hardness of the titanium alloy increases from 431.5 to 531.2 HV compared to that without ECAP treatment, i e, increases by 23.11%, and the tensile strength increases from 1 045.30 to 1 176.25 MPa, i e, increases by 12.5%.

Influence of heat treatments on incipient melting structures of DD5 nickel-based single crystal superalloy

The evolution of microstructure and formation mechanism of incipient melting microstructure of DD5 single crystal superalloy during solution heat treatment were studied by scanning electron microscopy(SEM),electron probe microanalysis(EPMA),and energy dispersive spectroscopy(EDS).The solidus and liquidus of single crystal alloy were obtained by differential scanning calorimetry(DSC).Results show that the mosaic-like eutectic and fan-like eutectic are dissolved at first,and the coarseγ'phase is dissolved later during the solution heat treatment of 1,390°C/2 h+1,310°C/4 h+1,320°C/10 h+air cooling(AC).The composition segregations of Al,Ta,W and Re are 0.99,0.96,1.04 and 1.16,respectively,which close to 1.The incipient melting is caused by the low local temperature of the alloy,and the micropore region with a lower melting point is the preferred position for incipient melting.

Hot Corrosion Resistance of TB8 Titanium Alloy after ECAP and Heat Treatment

The metastableβtitanium alloy TB8(Ti-12.76Mo-2.13Nb-2.73A1-0.16Si)was used as the original material,and the secondary processing method combining equal channel angular pressing(ECAP)and heat treatment was adopted.With the help of optical microscope(OM),scanning electron microscope(SEM)and X-ray diffractometer(XRD),the corrosion behavior of TB8 titanium alloy after different secondary processing(800℃/850℃solid solution-520℃aging,ECAP-800℃/850℃solid solution-520℃aging,and800℃/850℃solid solution-ECAP-520℃aging)was studied.The experimental results show that the hot corrosion products of the six samples are similar,mainly Na_(2)Si_(2)O_(5),MoS_(2),TiCl_(2),Ti(SO_(4))_(2),and TiS.Due to the grains of the TB8 titanium alloy treated by 850℃solid solution-ECAP-520℃aging are obviously refined,the surface structure is the most smooth and dense,forming a continuous Al2O3protective film,and the surface defects are the least after corrosion.Its corrosion layer thickness is the lowest(102.3μm),only 36.5%-81.4%of that of other secondary processing titanium alloys.In addition,the corrosion kinetics curves of the six materials all follow parabolic laws,and the minimum corrosion weight gain of the samples after 850℃solutionECAP-520℃aging treatment is 0.7507 mg·mm^(-2),showing better hot corrosion resistance.

Effects of aging treatment processes on microstructures and mechanical properties of AZ63 casting magnesium alloy

The effects of three different aging treatment processes,namely single-stage,double-stage,and reverse double-stage aging treatment processes,on the microstructures and mechanical properties of the AZ63(Mg-6Al-3Zn-0.25Mn)casting magnesium alloy were investigated and compared.The results indicate that the microstructures of all the aged alloys under the three treatment processes are mainly composed ofα-Mg,Mg17Al12),and Al4Mn phases,indicating that the double-stage and reverse double-stage aging treatments have no obvious effect on the type of alloy phases.However,as compared with the single-stage and double-stage processes,the reverse double-stage process has a great effect on the quantity of the Mg17Al12phases.After the reverse double-stage aging treatment,which results in a stronger drive for decomposition of the supersaturated solid solution,the number of Mg17Al12phases precipitated in the grains significantly increases.In addition,as compared with the single-stage aged alloy,the tensile properties at room temperature for both the double-stage and reverse double-stage aged alloys are significantly improved.Among them,the reverse double-stage aged alloy achieves the highest tensile strength,yield strength,and elongation of 295 MPa,167 MPa,and 8.6%,respectively.

Effect of heating temperature on the microstructure evolution of a Zn-Al-Mg coating on press-hardened steel

This paper addresses the microstructure evolution in the Zn-1.2Al-1.2Mg coating of press-hardened steel during heat treatment at temperatures ranging from 600 ℃ to 900 ℃.The presence of aluminum in the coating leads to substantial variation in the chemical composition and microstructure within the heat-treated layer.As the heat treatment temperature increases, the original Fe_(2)Al_(5) barrier layer between the coating layer and steel substrate is progressively dissolved and replaced by the aggregates of a new(FeAl) phase.At higher heat treatment temperatures, the(FeAl) phase gradually migrates to the subsurface layer of the coating.Meanwhile, Zn/Fe interdiffusion induces Γ-Fe_(3)Zn_(10)-phase formation in the original coating layer and α-Fe(Zn) solid solution formation at the zinc-substrate interface.These microstructure features suppress the high-temperature oxidation and evaporation of Zn.

Effects of Heat Treatment on Processing Characteristics of Pork

[Objectives]This study was conducted to explore the effects of heat treatment on processing characteristics of pork.[Methods]The effects of low-temperature long-term cooking(LTLT),high-temperature vacuum cooking,high-temperature cooking and high-temperature steaming on some indexes of pork products were studied,and principal component analysis was carried out.[Results]LTLT had significant effects on the total sensory score,moisture content,cooking loss rate,a value,shear force,and TBARS of pork,and the corresponding optimal product indicators were 71.40 points,72.36%,14.20%,4.79,7089.87 g,and 0.05 mg/kg,respectively.The microstructure changes in the LTLT group were relatively small,as the muscle fiber structure was relatively dense and uniform,and the gaps between muscle fibers were small.A total of 30 volatile flavor compounds were detected in the four groups,mainly alcohols,alkenes,alkanes,lipids,ketones,and aldehydes,and the LTLT group had more types and high contents.PCA analysis showed that the sensory evaluation,moisture content,elasticity,a value and LTLT were positively correlated with principal component 1.[Conclusions]Various indexes comprehensively showed that the LTLT group had better meat color,flavor,texture characteristics and lower oxidation degree than traditional cooking and steaming methods,which provides a theoretical reference for its large-scale application in the processing of prepared meat products.

Impact of Heat Treatments and Hole Density (p) on the Structural, Electrical, and Superconducting Properties of LnSrBaCu3O6+z (Ln = Eu, Sm, Nd) Compounds

In this study, we thoroughly examined the impact of heat treatments and hole count (p) on the properties of LnSrBaCu3O6+z (Ln = Eu, Sm, Nd) compounds. We focused on preparation, X-ray diffraction with Rietveld refinement, AC susceptibility, DC resistivity measurements, and heat treatment effects. Two heat treatment types were applied: oxygen annealing [O] and argon annealing followed by oxygen annealing [AO]. As the rare earth Ln’s ionic radius increased, certain parameters notably changed. Specifically, c parameter, surface area S, and volume V increased, while critical temperature Tc and holes (p) in the CuO2 plane decreased. The evolution of these parameters with rare earth Ln’s ionic radius in [AO] heat treatment is linear. Regardless of the treatment, the structure is orthorhombic for Ln = Eu, tetragonal for Ln = Nd, orthorhombic for Ln = Sm [AO], and pseudo-tetragonal for Sm [O]. The highest critical temperature is reached with Ln = Eu (Tc [AO] = 87.1 K). Notably, for each sample, Tc [AO] surpasses Tc [O]. Observed data stems from factors including rare earth ionic size, improved cationic and oxygen chain order, holes count p in Cu(2)O2 planes, and in-phase purity of [AO] samples. Our research strives to clearly demonstrate that the density of holes (p) within the copper plane stands as a determinant impacting the structural, electrical, and superconducting properties of these samples. Meanwhile, the other aforementioned parameters contribute to shaping this density (p).

On the Pre-Forging Heating Methods for AA2014 Alloy

The aluminium alloy AA2014 is one of the most widely used of the 2xxx series alloys, owing to its superior strength-to-weight ratio and stiffness. It is commonly forged to shape for use in aerospace parts. Three different small pilot-scale AA2014 billets were subjected to different heating operations, to physically simulate a pre-forge heating operation. The unheated sample and heated samples were then analysed for micro structural evolution and mechanical properties, to understand how the pre-forge heat treatments may vary the starting condition of the alloy before being forged. It was shown that an induction heating process has the greatest impact upon the precipitation distribution. Whilst this variation is commonly considered a negative impact, the opportunity to control the induction heating to promote preferential microstructure at specific locations within the billet may be possible.