Effects of Heating and Hot Extrusion Process on Microstructure and Properties of Inconel 625 Alloy

The effects of the heating process and hot extrusion on the microstructure and properties of inconel 625 alloy were studied. The experimental results showed that the properties of Inconel 625 alloy could be improved through the heating process and hot extrusion concomitant with a reduced corrosion rate. The M23C6 carbide, generated in the heating process, was retained and distributed at the grain boundary during the process of hot extrusion, which had an important influence on both elongation and corrosion resistance. The improvement of the comprehensive properties of the material, as measured by a tensile test at room temperature, was correlated with the dissolution of segregation Nb. A typical ductile fracture changed to a cleavage fracture where secondary cracks could be clearly seen. With the increase of the extrusion ratio, the real extrusion temperature was higher, which led to more dissolution of the M23C6 carbide, decreased the number of secondary cracks, enhanced the effect of solid solution strengthening, and reduced the intergranular corrosion rate. Under the condition of a high extrusion ratio and a high extrusion speed, the less extrusion time made it possible to obtain organization with a smaller average grain size. Moreover, in this case, the M23C6 carbide and segregated Nb did not have enough time to diffuse. Thus all samples exhibited medium strengths and corrosion rates after extrusion.

Effect of hot extrusion and heat treatment on microstructure of nickel-base superalloy

Effects of hot extrusion (HEX) and heat treatment on prior particle boundary (PPB), MC carbides,γ′precipitates and grain size of nickel-base FGH96 superalloy were studied. The results show that PPB consists of largeγ′, MC carbides enriched with Ti, Nb and a modicum of oxides. Thereafter, it can efficaciously tune γ′ precipitate size from micrometer down to nanometer region and simultaneously results in the annihilation of PPB by HEX process. The activation energy for grain growth of as-HEXed FGH96 superalloy was measured to be 402.6 kJ/mol, indicating that γ′ precipitate serves the critical role in inhibiting grain growth under sub-solvus heat treatment. Moreover, the results reveal that grain growth is primarily restrained by MC carbide in the case of super-solvus temperature.

Age-hardening behavior and microstructure of Cu-15Ni-8Sn-0.3Nb alloy prepared by powder metallurgy and hot extrusion

Cu-15Ni-8Sn-0.3Nb alloy rods were prepared by means of powder metallurgy followed by hot extrusion.Element maps obtained by electron probe micro analyzer(EPMA)showed that Nb-rich phases were formed and distributed within grains and at grain boundaries of the Cu-15Ni-8Sn-0.3Nb alloy.Transmission electron microscope(TEM)results indicated that there was no obvious orientation relationship between these phases and the matrix.Spinodal decomposition and ordering transformation appeared at early stages of aging at400°C and caused significant strengthening.Cu-15Ni-8Sn-0.3Nb alloy exhibited both higher strength(ultimate tensile strength>1030MPa)and higher tensile ductility(elongation>9.1%)than Cu-15Ni-8Sn alloy after aging treatment.The improvement was caused by Nb-rich phases at grain boundaries which led o the refinement of grain size and postponed the growth of discontinuous precipitates during aging.

Effect of hot extrusion on microstructure and tribological behavior of Al_(2)O_(3p) reinforced 7075 aluminum-matrix composites

The effects of hot extrusion and addition of Al_(2)O_(3p) on both microstructure and tribological behavior of 7075 composites were investigated via optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectrometry(EDS),and transmission electron microscopy(TEM).The experimental consequences reveal that the optimal addition of Al_(2)O_(3p) was 2 wt%.After hot extrusion,the Mg(Zn,Cu,Al)2 phases partially dissolve into the matrix and generate many uniformly distributed aging precipitation particles,the Al_(7)Cu_(2)Fe phases are squeezed and broken,and the Al_(2)O_(3p) become uniform distribution.The microhardness of as-extruded 2 wt%Al_(2)O_(3p)/7075 composites reaches HV 170.34,increased by 41.5%than as-cast composites.The wear rate of as-extruded 2 wt%Al_(2)O_(3p)/7075 composites is further lower than that of as-cast composites under the same condition.SEM-EDS analyses reveal that the reinforced wear resistance of composites can put down to the protective effect of the Al_(2)O_(3p) reinforced transition layer.After hot extrusion,the transition layer becomes stable,which determines the reinforced wear resistance of the as-extruded composites.

Effects of hot extrusion on microstructure and mechanical properties of Mg matrix composite reinforced with deformable TC4 particles

Mg matrix composites were often reinforced by non-deformable ceramic particles.In this paper,a novel Mg matrix composite reinforced with deformable TC4(Ti-6Al-4 V)particles was fabricated and then extruded.The evolutions of microstructure and mechanical properties of the composite during hot extrusion were investigated.Hoi extrusion refined giains and eliminated the segregation of TC4 particles.TC4 particles,as deformable particles,stimulated the nucleation of dynamic recrystallization during extrusion.However,since the deformation of TC4 particles partly released the stress concentrations around them,the recrystallized grains are just slightly smaller around TC4 particles than that away from them,which is evidently different from the case in Mg matrix composites reinforced by non-deformable ceramic particles.Compared with AZ91 matrix composites reinforced by SiC particles,the present composite possesses the superior comprehensive mechanical properties,which are attributed to not only the strong interfacial bonds between TC4p and matrix but also the deformability of TC4 particles.

Effect of hot extrusion process on microstructure and mechanical properties of hypereutectic Al-Si alloys

The hypereutectic Al-Si alloy was fabricated by hot extrusion process after solidified under electromagnetic stirring,and the microstructure and mechanical properties of the alloy were studied.The results show that the ultimate tensile strength and elongation of the alloy reached 229.5 MPa and 4.6%,respectively with the extrusion ratio of 10,and 263.2 MPa and 5.4%,respectively with extrusion ratio of 20.This indicates that the mechanical properties of the alloy are obviously improved with the increase of extrusion ratio.After hot extruded,the primary Si,eutectic Si,Mg2Si,AlNi,Al7Cu4Ni and Al-Si-Mn-Fe-Cr-Mo phases are refined to different extent,and the efficiency of refinement is obvious more and more with the increase of extrusion ratio.After T6 heat treatment,the sharp corners of these phases become passivated and roundish,and the mechanical properties are improved.The ultimate tensile strength of the extruded alloy after T6 heat treatment reaches 335.3 MPa with extrusion ratio of 10 and 353.6 MPa with extrusion ratio of 20.

Effect of extrusion ratio on microstructure and mechanical properties of AZ91D magnesium alloy recycled from scraps by hot extrusion

A method for recycling AZ91D magnesium alloy scraps directly by hot extrusion was studied.Various microstructural analyses were performed using the techniques of optical microscopy,scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).Microstructural observations revealed that all the recycled specimens consisted of fine grains due to the dynamic recrystallization.The main strengthening mechanism of the recycled specimen was grain refinement strengthening and homogeneous distribution of oxide precipitates.The interfaces of individual scraps of extruded materials were not identified when the scraps were extruded with the extrusion ratio of 40-1.Oxidation layers of the scraps were broken into pieces by high compressive and shear forces under the extrusion ratio of 40-1.The ultimate tensile strength and elongation to failure increased with increasing the extrusion ratio.Recycled specimens with the extrusion ratio of 40:1 showed higher ultimate tensile strength of 342.61 MPa and higher elongation to failure of 11.32%,compared with those of the cast specimen.

Effect of hot extrusion on microstructure and mechanical properties of quasicrystal-reinforced Mg-Zn-Yalloy

The microstructure and mechanical properties of as-cast and as-extruded Mg-Zn-Y alloy （Mg-11%Zn-0.9%Y, mass fraction） containing Mg3YZn6 quasicrystal were studied. The eutectic icosahedral quasicrystal phase （I-phase） is broken and almost distributes along the extrusion direction, and fine I-phase with nano-size is precipitated during the extrusion. The α-Mg matrix grains are refined due to recrystallization occuring during the hot extrusion. Some {1012} twins are observed in the extruded ZW1101 alloy. And {0002}〈1010〉 fiber texture is formed in matrix alloys after hot extrusion. The extruded alloy exhibits high strength in combination with large elongation at room temperature. The strengthening mechanism of the as-extruded alloy was discussed.

Effect of Hot Extrusion on Microstructure and Properties of (ABOw+SiCp)/6061Al Composites Fabricated by Semi-solid Stirring Technique

6061Al matrix composites reinforced by 5vol.%ABOw and 15vol.%SiCp were fabricated by semi-solid stirring technique successfully at 640 ℃ for 40min with the stirring rate of 300 rpm,and the composites were extruded at a temperature of 500 ℃ using an extrusion ratio of 25:1 subsequently.Tensile tests were performed on as-casted and as-extruded(ABOw+SiCp)/6061Al composites at room temperature,and microstructures were observed by scanning electron microscope(SEM).SEM investigation showed that the as-extruded composite exhibited reduced porosity as well as a more uniform distribution of the reinforcements compared with the as-casted composite.The tensile tests results showed that the ultimate tensile strength and tensile elongation of as-extruded composite are higher than that of as-casted composite.

Research on microstructure and high-temperature friction and wear properties of a cobalt-based alloy for hot extrusion die

The hot extrusion die is a key tool for determining the surface quality and dimensional accuracy of extruded products.Because its service process is subject to high temperature,high pressure,and wear,it must be resistant to these conditions.In this paper,the high-temperature friction and wear properties of a cobalt(Co)-based alloy were investigated and compared with those of a titanium carbide(TiC)cemented material.The results show that the high-temperature wear performance of the Co-based alloy is better than that of the TiC cemented material,and that Co-based materials have the potential for replacing TiC cemented materials as hot-extrusion-die materials.Due to the high density and good combination of the matrix and carbide,the carbides do not easily peel off from the matrix during the wear process.Due to the higher impact toughness of the Co-based alloys,microcracks that can cause worn-surface peeling are not easily generated.As a result,the high-temperature wear performance of Co-based alloys is found to be better than that of TiC cemented materials.

Effects of hot extrusion and annealing treatment on microstructures,properties and texture of AZ31 Mg alloy

Effects of extrusion deformation and heat treatment on microstructures, mechanical properties and texture of AZ31 Mg alloy were investigated. The results show that the microstructures of as-cast AZ31 alloy are markedly refined after hot extruding, the average grain size is about 25 urn and strong fiber texture <1010> exists in the extruded AZ31 alloy. The mechanical properties are improved obviously. The grain size is somewhat inhomogeneous and strip structure emerges along the extrusion direction due to incomplete dynamic recrystallization during the extrusion process. With increasing annealing temperature, the small grain grows up and turns into equiaxed grain, and the texture is weakened with the visible growing up of grains.

Influence of hot extrusion on microstructure and mechanical properties of AZ31 magnesium alloy

Extrusion treatment is a common method to refine the grain size and improve the mechanical properties of metal material. The influence of hot extrusion on microstructure and mechanical properties of AZ31 magnesium alloy was investigated. The results show that the mechanical properties of AZ31 alloy are obviously improved by extrusion treatment. The ultimate tensile strength (UTS) of AZ31 alloy at room temperature is measured to be 222 MPa, and is enhanced to 265.8 MPa after extrusion at 420℃. The yield tensile strength (YTS) of AZ31 alloy at room temperature is measured to be 84 MPa, and is enhanced to 201 MPa after extrusion at 420℃. The effective improvements on mechanical properties result from the formation of the finer grains during extrusion and the finer particles' precipitated by age treatment. The features of the microstructure evolution during hot extruded of AZ31 alloy are dislocation slipping on the matrix and occurrence of the dynamic recrystallization.

Evolution of microstructure and texture of AZ80 magnesium alloy under hot torsion with constant decreasing temperature rate

Hot torsion tests for AZ80 magnesium alloy were carried out in the temperature range of 380℃-260℃,with a constant decreasing temperature rate of 10℃/s in order to weaken the basal texture and refine the grains.The results indicated that the average grain sizes were refined forming gradient structure with increasing specimen radial position from center(12.2-5.4μm),and that the initial basal texture intensity of the extruded magnesium alloy was weakened from 46.2 to 8.3.Furthermore,the extension twins(ETs)could be disintegrated from the twins forming separated twins with smaller sizes.Interestingly,ETs with the same twin variant intersecting with each other could be coalesced forming grains with similar orientation,while ETs with different twin variants were separated by twins boundaries contributing to grain refinement.Moreover,in addition to the conventional continuous dynamic recrystallized(CDRX)grains with 30˚orientation rotated around C-axis of the parent grains,CDRXed grains with 30˚rotation around a-axis and random rotation axis were also discerned.Besides,the CDRX evolution induced twins were also elaborated,exhibiting the complex competition between CDRX and twining.Hot torsion deformation with constant decreasing temperatures rate is an effective way of grain refinement and texture modification.

Effect of Gd Addition on Hot Deformation Behavior and Microstructure Evolution of 7075 Aluminum Alloy

In order to clarify the effect of rare earth Gd on the microstructure evolution and deformation behavior of 7075 aluminum alloy during hot compression,uniaxial compression tests of Al-Zn-Mg-Cu-0.5%Gd were conducted at strain rates of 0.001,0.01,0.1,and 1 s^(-1)with the temperatures ranging from 350 to 450℃.The microstructural evolution during deformation was characterized using optical microscopy and electron backscatter diffraction(EBSD)techniques.The experimental results indicate that the addition of the rare earth element Gd significantly increases the peak flow stress and thermal activation energy of the alloy.Due to the pinning effect of rare earth phases,dislocation movement is hindered,leading to an increased level of work hardening in the alloy.However,the dynamic recrystallization of the alloy is complicated.At a high Z(Zener-Hollomon parameter)values,recrystallization occurs in the form of DDRX(Discontinuous Dynamic Recrystallization),making it easier to nucleate at grain boundaries.As the Z value decreases gradually,the recrystallization mechanism transitions from discontinuous dynamic recrystallization(DDRX)to continuous dynamic recrystallization(CDRX).At a low Z values with the strain rate of 0.001 s^(-1),the inhibitory effect of rare earths weakens,resulting in a comparable recrystallization ratio between Al-Zn-Mg-Cu-Gd alloy and 7075 aluminum alloy.Moreover,the average grain size of the aluminum alloy with Gd addition is only half that of 7075 aluminum.The addition of Gd provides Orowan and substructure strengthening for the alloy,which greatly improves the work-hardening of the alloy compared with 7075 aluminum alloy and improves the strength of the alloy.

Effect of hot isostatic pressure on the microstructure and tensile properties of γ'-strengthened superalloy fabricated through induction-assisted directed energy deposition

The microstructure characteristics and strengthening mechanism of Inconel738LC(IN-738LC) alloy prepared by using induction-assisted directed energy deposition(IDED) were elucidated through the investigation of samples subjected to IDED under 1050℃ preheating with and without hot isostatic pressing(HIP,1190℃,105 MPa,and 3 h).Results show that the as-deposited sample mainly consisted of epitaxial columnar crystals and inhomogeneously distributed γ’ phases in interdendritic and dendritic core regions.After HIP,grain morphology changed negligibly,whereas the size of the γ’ phase became increasingly even.After further heat treatment(HT,1070℃,2 h + 845℃,24 h),the γ’ phase in the as-deposited and HIPed samples presented a bimodal size distribution,whereas that in the as-deposited sample showed a size that remained uneven.The comparison of tensile properties revealed that the tensile strength and uniform elongation of the HIP + HTed sample increased by 5% and 46%,respectively,due to the synergistic deformation of bimodal γ’phases,especially large cubic γ’ phases.Finally,the relationship between phase transformations and plastic deformations in the IDEDed sample was discussed on the basis of generalized stability theory in terms of the trade-off between thermodynamics and kinetics.

Microstructure and mechanical properties of Al-6Zn-2.5Mg-1.8Cu alloy prepared by squeeze casting and solid hot extrusion

Al-6Zn-2.5Mg-1.8Cu alloy ingots were prepared by squeeze casting under different specific pressures,and the fresh ingot with best mechanical properties was solid hot extruded.With the increase of the specific pressure from 0 to 250 MPa,the dendrites became round and small.Because the applied pressure increased the solid solubility of alloying elements,the number of MgZn2 phases decreased.When the specific pressure increased from 250 MPa to 350 MPa,the grain size increased.After solid hot extrusion,the a（Al） grains were refined obviously and the MgZn2 phases were uniformly dispersed in the microstructure.After solid hot extrusion,the ultimate tensile strength was 605.67 MPa and the elongation was 8.1%,which were improved about 32.22%and15.71%,respectively,compared with those of the metal mold casting alloy.The fracture modes of the billet prepared by the metal mold casting and by squeeze casting were intergranular and quasi-cleavage fractures,respectively,whereas,that of the solid hot extrusion was mainly dimple fracture.The refined crystalline strengthening was the main reason to improve the strength and elongation of alloy.

Experimental research and application of cold cutting to hot stamping parts based on multiphase microstructure

Among the bottlenecks that hinder the improvement of the production efficiency of hot stamping are high strength and difficulty in edge cutting and hole punching.Starting from the preparation of hot stamping multiphase microstructure materials,this paper developed a plate quenching die system with controllable surface temperature and prepared four types of hot stamping plates with different martensite volume fractions.Then,straight edge cold cutting experiments were performed to study the influence of cutting clearance and cutting force on fracture quality.The results show that the bright zone is the largest when the cutting clearance is 0.14 mm,and the cutting experience coefficient of the hot stamping sheet with each martensite volume fraction is obtained when the cutting clearance is 0.14 mm.The research results of this paper were applied to the production of hot stamping parts.

Microstructure and corrosion behavior of as-cast ADC12 alloy with rare earth Yb addition and hot extrusion

The effects of rare earth ytterbium(Yb)addition and hot extrusion on the microstructure and corrosion behavior of as-cast ADC12 were studied by optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and X-ray diffraction(XRD).The experimental results demonstrate that both the Si phase andβ-Al5FeSi phase in the alloy with 0.9 wt%Yb have been remarkably refined,and the Al3Yb intermetallic compound has also been obtained.The Si,β-Al5FeSi,and rare earth phases are further refined in the alloy at 0.9 wt%Yb and hot extrusion.The results of the immersion corrosion tests and electrochemical experiments show that the corrosion current density(8.56μA/cm2)of the alloy with 0.9 wt%Yb addition and hot extrusion is 50.6%lower than the untreated alloy(17.33μA/cm2),and the polarization resistance(9252Ω·cm2)was 71.3%higher than the untreated alloy(2654Ω·cm2).The corrosion in the cathode phase in the micro-battery was refined to varying degrees attributable to the addition of Yb and hot extrusion,where the cathode reaction in the corrosion process caused a decrease of the corrosion rate.

Hot deformation behavior and microstructure evolution of Be/2024Al composites

The high temperature compression test of Be/2024Al composites with 62wt%Be was conducted at 500–575℃ and strain rate of0.003–0.1 s^(-1).The strain-compensated Arrhenius model and modified Johnson–Cook model were introduced to predict the hot deformation behavior of Be/2024Al composites.The result shows that the activation energy of Be/2024Al composites was 363.364 k J·mol^(-1).Compared with composites reinforced with traditional ceramics,Be/2024Al composites can be deformed with ultra-high content of reinforcement,attributing to the deformable property of Be particles.The average relative error of the two models shows that modified Johnson–Cook model was more suitable for low temperature condition while strain-compensated Arrhenius model was more suitable for high temperature condition.The processing map was generated and a hot extrusion experiment was conducted according to the map.A comparation of the microstructure of Be/2024Al composites before and after extrusion shows that the Be particle deformed coordinately with the matrix and elongated at the extrusion direction.

Role of extrusion rate on the microstructure and tensile properties evolution of ultrahigh-strength low-alloy Mg-1.0Al-1.0Ca-0.4Mn(wt.%)alloy

Mg-1.0Al-1.0Ca-0.4Mn(AXM1104, wt.%) low alloy was extruded at 200 ℃ with an extrusion ratio of 25 and different ram speeds from 1.0 to 7.0 mm/s. The influence of extrusion rate on microstructure and mechanical properties of the AXM1104 alloy was systematically studied. With the increasing of extrusion rate, the mean dynamically recrystallized(DRXed) grain size of the low alloy and average particles diameter of precipitate second phases were increased, while the degree of grain boundary segregation and the intensity of the basal fiber texture were decreased. With the rising of extrusion rate from 1.0 to 7.0 mm/s, the tensile yield strength(TYS) of the as-extruded AXM1104 alloy was decreased from 445 MPa to 249 MPa, while the elongation to failure(EL) was increased from 5.0% to 17.6%. The TYS, ultimate tensile strength(UTS) and EL of the AXM1104 alloy extruded at the ram speed of 1.5 mm/s was 412 MPa, 419 MPa and 12.0%, respectively,exhibiting comprehensive tensile mechanical properties with ultra-high strength and excellent plasticity. The ultra-high TYS of 412 MPa was mainly due to the strengthening from ultra-fine DRXed grains with segregation of solute atoms at grain boundaries. The strain hardening rate is increase slightly with increasing extrusion speed, which may be ascribed to the increasing mean DRXed grain size with rising extrusion speed. The higher strain hardening rate contributes to the higher EL of these AXM1104 samples extruded at higher ram speed.