Effect of heat treatment on the microstructure and hardness of C-Cr-W-Mo-V-RE Fe-based hardfacing layer

After different heat treatment processes, the metal compound, the microstructure and the hardness of the C-Cr-W- Mo-V-RE Fe-based hardfacing layers are investigated by means of metallographic microscope, X-ray diffraction （ XRD ）, energy dispersive spectrum（ EDS ）, transmission electron microscope（TEM） and hardness tester. The results show that the hardfacing layers have higher tempering stability and secondary hardening property. After quenching at 820 ℃ ,the hardness value（ HRC37 ） and the microstructure of the layers are similar to that normalized at 820 - 1 000 ℃. The tempering stability and the hardness increases with increasing quench temperature, which is attributed to the amount of the alloy element in the matrix. These results are very helpful for improving the mechanical properties of the hardfacing layers.     

Effect of heat treatment on microstructure and properties of hot-extruded nickel-aluminum bronze

The effect of heat treatment on the microstructure and properties of a hot-extruded nickel-aluminum bronze was investigated. Experimental materials were heat treated through different processes, including quenching, normalizing, aging and annealing, and their microstructure, corrosion resistance and mechanical properties were characterized. It is found that quenching causes all β phase transformed into β phase, however, normalizing causes β phase transformed into β α and κ phases. When the quenched sample is aged, fine phase is precipitated from the as-quenched microstructure of β＇ phase. Annealing causes the transformation of β into a and κ phases. The results of mechanical property tests show that quenching, normalizing and aging improve the tensile strength and hardness of the experimental material, with a corresponding fall in elongation. Annealing raises the elongation but reduces the tensile strength and hardness. Furthermore, corrosion resistance of nickel-aluminum bronze ranks from worse to better in the following order： aged, quenched, normalized, hot-extruded and annealed. However, with the exposure time of corrosion test increasing, the difference of average corrosion rate between those nickel-aluminum bronzes tums small.     

Effect of rolling and heat treatment on microstructure and properties of Ti-26 sheet

The effect of heat treatment and rolling process on the properties and microstructures of Ti-26 （Ti-15V-3Al-3Cr-3Sn-Forming） sheet was studied. The results show that the best rolling temperature for Ti-26 alloy is in the temperature range from 900 ℃ to 950℃. Under this condition, the resistance of deformation and yield ratio are low and the alloy has better hot work ability. The alloy will achieve better mechanical properties and completely recrystallized β microstructure when the deformation ratio is not less than 60% and the solution temperature is 30 ℃ above the phase transformation temperature. The best heat treatment conditions are recommended as： 790℃, 30 min, AC or WQ followed by 510 ℃, 10 h, AC. Under this heat treatment condition the strength of the Ti-26 alloy is 1 230 MPa and the elongation is 15%.     

Characterization of the microstructure and hardness of the HAZ in a 800MPa grade RPC steel

0Introduction Intheprojectof“NewGenerationSteelMaterials”, oneoftheeffectiveapproachestoachieve800MPagrade steelsistoadoptRPCphasetransformationtechnique[1]. Atpresent,12 millimeter thickplatesteelwithyield strengthover800MPahasbeenobtainedbymeansofthis…     

Effect of plastic deformation on microstructure and hardness of AlSi/A1 gradient composites

The effects of plastic deformation on the evolution of microstructure and micro-hardness were studied on plates made from a cylindrical ingot of AISi/AI aluminum composite. This ingot was produced by double-stream-pouring continuous casting（DSPCC）. The results show that the three layers, i.e. the external pure aluminum, internal AI-Si alloy and the transition gradient layer, are maintained after compression as well as rolling processing. With the decrease in thickness of the gradient composite plate, the fluctuation of micro-hardness in transition layer in the direction normal to the applied force is significantly reduced. A simplified lamination model was used to evaluate qualitatively the micro-hardness distribution in the direction parallel to the applied force. However, the model is invalid in the explanation of the fluctuation of the micro-hardness in the direction normal to the applied force. The micro-hardness distribution variation in this direction is mainly attributed to the deformation of a（Al） matrix incorporated the dissolution and spheroidization of eutectic silicon phase.     

Effect of vacuum heat treatment on microstructure and microhardness of cold sprayed Cu-4Cr-2Nb alloy coating

The effect of vacuum heat treatment on the microstructure and microhardness of cold-sprayed Cu-4%Cr-2%Nb alloy coating was investigated. The heat treatment was conducted under the temperatures from 250 ℃ to 950 ℃ with a step of 100 ℃ for 2 h. It was found that a dense thick Cu-4Cr-2Nb coating could be formed by cold spraying. After heat treatment, a Cr2Nb phase was uniformly distributed in the matrix, which was transferred from the gas-atomized feedstock. A little grain growth of Cr2Nb phase was observed accompanying with the healing-up of the incomplete interfaces between the deposited particles at the elevated temperatures. The coating microhardness increases a little with increasing the temperature to 350 ℃, and then decreases with further increasing temperature up to 950 ℃. This fact can be attributed to the microstructure evolution during the heat treatment.     

Effect of prior heat treatment on microstructure and mechanical properties of 0·23% carbon dual phase steel

Abstract

The present study is aimed at understanding the effect of prior heat treatment on the microstructure and mechanical properties of 0·23% carbon dual phase steel. The as received steel was subjected to annealing, normalising and hardening treatment before actual dual phase heat treatment. These steels along with the as received steel were intercritically annealed at 745°C followed by water quenching in order to produce a dual phase microstructure consisting of varying quantities and morphologies of ferrite and martensite. Mechanical properties were evaluated by tensile testing and hardness measurement. It was found that prior heat treatment affects the final dual phase microstructure in terms of size and relative amount of ferrite and martensite. It was also found that dual phase treatment resulted in improved mechanical property. Optimum combination of strength and ductility was obtained with the steel subjected to prior hardening (DPLA-3) treatment. The maximum in ultimate tensile strength (762 MPa) was obtained with the steel subjected to prior annealing treatment (DPLA-1). The X-ray diffraction study confirmed the presence of carbides in DPLA-1 steel, which contribute to the increased strength by precipitation hardening.     

Study on the microstructure and hardness of in-service welded joint of X70 pipeline steel

Hydrogen induced cracking （HIC） is one of the main problems of in-service welding onto active pipeline. Microstructure and hardness of welded joint have a vital effect on hydrogen induced cracking. The microstructure and hardness of welded joint of XTO pipeline steel were studied using simulation in-service welding device. The results show that the main microstructures of in-service welded seam are grain boundary ferrite , intracrystalline acicular ferrite , as well as small amount of widmanztatten structure. The main microstructures of coarse grain heat-affected zone （CGHAZ） are coarse granular bainite, lath ferrite and martensite. Metastable phases such as martensite and lath ferrite are found in CGHAZ because of the too quick cooling velocity a＇nd the hardness of the CGHAZ is high.     

Effect of heat treatment on thermal stability of Ti40 alloy

Five new heat treatment processes were designed, which were divided into three groups by their characteristics. The microstructures and mechanical properties of the alloy after the five heat treatments and thermal exposure at 500, 550℃ for 100 h were tested. The results indicate that a little differences exist in the performance of mechanical properties at room-temperature after the five heat treatments, and the thermal stability is the key factor for determining heat treatment process. Among the three groups of heat treatment processes, the best thermal stability is achieved after the first group of heat treatment. After annealing treatment at intermediate temperature, some defects and uneven grain boundaries are remained, which leads to the reduction fractions of precipitations on unit grain boundary and the harmful effect of precipitations on grain boundary is weakened. The process of annealing at 650 ℃for 4 h is recommended the best heat treatment process for Ti40 alloy.     

Effect of composition and heat treatment on the structure and properties of Fe−Ni−Be invar alloys

Conclusions Addition of Be (0.5–1%) to Fe–Ni invar alloys provides dispersion hardening after quenching and aging, with retention of a low (close to invar) value of LCTE. Increase of the Be concentration in alloy 36N is accompanied by an increase in LCTE in the quenched as well as the aged condition, and increase of the Ni concentration to 38–41% at a fixed concentration of Be leads to a decreased value of LCTE in the aged alloys, approaching that of the alloy 36N. The optimum composition range for Fe–Ni–Be alloys in which the best combination of properties can be obtained — low value of LCTE (3.10^–6, K^–1) and higher strength (_0.2910 N/mm², _u1100 N/mm²) — was determined to be (39–40% Ni, 0.7–0.8% Be). The alloy 40NL (40% Ni, 0.8% Be) is proposed as a high strength invar alloy.I. P. Bardin Central Scientific-Research Institute for Ferrous Metallurgy (TsNIIChERMET). Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 33–36, February, 1992.     

Effect of heat treatment on microstructure and high temperature tensile properties of cast nickel-base superalloy with high W, Mo and Nb contents

The microstructural features and high temperature tensile properties of M963 superaUoy at as-cast, as-solutioned and as-aged conditions were investigated in detail. The results show that the solution treatment at 1220℃ for 4 h,AC causes an increase in high temperature yield strength but a drastic drop in high temperature ductility due to the precipitation of both the secondary carbide M6C along grain boundaries and at the interdendritic regions and very fine γ‘ particles in the dendrite cores. Aging treatment following the solution treatment can improve the high temperature tensile properties of M963 superalloy due to the coaraing of the γ’ precipitate. One stage aging at 850℃ for 16 h following the solution treatment causes an increase in both strength and ductility d alloy M963, and two-stage aging of 1089 ℃/2 h, AC plus 850℃/16 h, AC following the solution treatment further increases the ductility d alloy M963 but slightly decreases its strength.     

Effect of heat treatment on eutectic silicon morphology and mechanical property of AI-Si-Cu-Mg cast alloys

Through morphology observation on silicon particles of A1-Si-Cu-Mg cast alloy, it is found that during solution treatment the evolution of eutectic silicon morphology and their effect on mechanical properties can be classi-fied into three stages. In the initial stage, necking, stubbing and fragmentation of silicon particles result in the im-provement of plasticity of alloy. In the intermediate stage, the mechanical properties of 354 alloy attain peak values due to spheroidization of silicon particles. In the final stage, the drop of hardness and strength is related to the dete-rioration of silicon morphology. The facets and lap occur in silicon particles and the coarsening process of silicon fol-lows LSW model. During aging, the clusters of excess silicon can work as barriers for dislocation movement and thus enhance the strength of alloy. On the other hand, excess Si affects the process of aging precipitation and leads to a fine and highly dense distribution of GP zones, finally effectively strengthens the alloy.     

Effect of heat treatment on eutectic silicon morphology and mechanical property of Al-Si-Cu-Mg cast alloys

1　INTRODUCTIONCastAl Sibasealloysareoneofthemostimpor tantaluminumalloysattributedtotheirlowdensity ,highspecificstrength ,excellentcasting properties ,mechanicalpropertiesanderosionresistance .TheseAl Sialloysaremainlyappliedinautomotive ,aerospace ,transportationandmechanicalindustry ,etc[1,2 ] .The propertiesofalloyscanbeimprovedthroughaddingCuandMgelementsintothealloys .Inthe processofsolutiontreatment ,alloyingele mentscompletelydissolveandformsupersaturatedsolidsolution .However…     

Effect of heat treatment on the crystal structure of deformed samples of chromium–manganese steel

Results of studying microstructures and the crystal structure of samples of 35KhGF steel (0.31–0.38 wt % С, 0.17–0.37 wt % Si, 0.95–1.25 wt % Mn, 1.0–1.3 wt % Cr, 0.06–0.12 wt % V, and the remainder was Fe) have been presented. The samples have been selected from hot-rolled pipes subjected to different heat treatments. A study has been carried out in order to explain the choice of the heat-treatment regime based on determining the structure–properties relationship that provides an increase in the corrosion resistance of pipes to the effect of hydrocarbons. Methods of the energy-dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD) have been used. In the microstructure of samples, oxide inclusions and discontinuities with sizes of 1–50 μm that presumably consist of the scale were detected. The ferrite grain size and the orientations of crystals were determined; the data on the local mechanical stresses in the Taylor orientation- factor maps were obtained. The grain refinement; the increase in the fraction of the low-angle boundaries; and the decrease in the local mechanical stresses and, therefore, the highest corrosion resistance to the effect of hydrocarbons is achieved by normalizing at 910°С.     

Effect of lithium on the casting microstructure of Cu-Li alloys

The effect of lithium on the casting microstructure of Cu-Li alloys was studied via the Wild MPS 46 Automatic camera, Deitz Diaplan, and scanning electron microscope. The result shows that trace lithium added to copper coarsens the grains of Cu-Li alloys in eqniaxed crystal area because of the excellent purification effect. With the amount of lithium increasing, the average grain size increases sharply. But when the amount of lithium increases more, the average grain size decreases instead. At the same time, the typical dentritic crystal area of copper is diminished when lithium is added to pure copper.     

Effect of heat treatment on shape memory properties of ductile CuAlMn alloys

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Influence of yttrium on microstructure and properties of Ti-23Al-25Nb alloy after heat treatment

The existence of yttrium in Ti-23Al-25Nb alloy and its influence on the microstructure after heat treatment of Ti-23Al-25Nb alloy were investigated using thermal analysis（DTA）, EPMA, XRD and SEM. The heat treatment was determined based on DTA measurements. The compression tests at room temperature were performed on a Instron-569 universal tester. The results show that yttrium exists as the Y2O3 alloy. The addition of Y doesn＇t affect the characteristic phase transformation temperature At lower quenching temperature, Y strengthens the XRD peaks of O phase by improving the decomposition of B2 phase. Yttrium addition enhances the compression properties with the compression strength, yield strength and compression ratio increasing. The strengthening is attributed to the second phase strengthening of Y2O3 particles and the grain refinement.