Showing papers in "Materials for Mechanical Engineering in 2010"

Heat Treatment Process for CLF-1 Reduced Activation Ferritic/Martensitic Steel

Abstract: The effects of heat treatment parameters on microstructure and mechanical properties of reduced activation ferritic/martensitic(RAFM) steels were investigated by microhardness test,microstructure observation and tensile test at room temperature.The feasible heat treatment process was determined.The results show that good microstructure and mechanical properties of the steel were obtained after solution treated at 980 ℃ for 45 min and tempered at 740 ℃ for 90 min,that the tensile strength was 760 MPa and the elongation was 19.5%,which could satisfy its working need.The recrystallization temperature was about 780 ℃,the transformation temperature from α phase region to α and γ two-phase region was about 820 ℃,γ single-phase region temperature was slightly higher than 920 ℃.

Temperature Simulation of Single Pass Hot Rolling Process of Aluminum Alloy

Abstract: In order to accurately predict the temperature field of rolled pieces,optimize the hot rolling process and improve the quality of the final product,the finite element temperature model of 3104 aluminum alloy plate during single pass hot rollig process was built up using MSC,Marc softwares by rolling test and two-dimensional elastoplastic finite element method.The effects of air cooling,contact heat transfer,plastic deformation heat and friction heat on the plate temperature were investigated.And the effects of rolling parameters including the initial temperature of plate rolling speed,contact heat transfer coefficient and reduction on temperature drop sensitivity coefficient were analyzed also.The results show that contact heat transfer had the most effect on the plate temperature and it was followed by plastic deformation,friction and air cooling.The initial temperature had the most effect on the temperature drop sensitivity coefficient and it was followed by rolling speed,contact heat transfer coefficient and reduction.

Research Progress of Burning-Resistant Technology of Titanium Alloy

Abstract: The reason and mechanism of titanium alloy combustion are reviewed.The present status of burning-resistant technologies(including burning-resistant coating,buring-resistant titanium alloy and surface alloying)of titanium alloy are also discussed.Double glow plasma discharge technology,as a new surface alloying technology with great potential,is mainly described.Some suggestions are put forward for future direction in the research.

Compression and Energy Absorption Properties of Gradual Porous Aluminum Alloy

Abstract: Gradual porous aluminum alloys were prepared by infiltration method.Compression tests were carried out for the porous aluminum alloys with different relative densities.Compressive yield strength and energy absorption properties were investigated.The results show that the compressive stress-strain curves of the alloys consisted of two distinct regions,i.e.,elastic deformation region and plastic collapse region.The relationship between the compressive yield strength and relative density could be described with Ashby-Gibson's model.The compressive yield strength and energy absorption capability of the alloys gradually increased with relative density increasing.

Dynamic Recrystallization Behavior and Power Dissipation Map of Mn18Cr18N Retaining Ring Steel

Abstract: To control the microstructure and properties of retaining ring steel after hot forging,the dynamic behavior of Mn18Cr18N retaining ring steel was investigated by thermomechanical compression test under the conditions of experimental temperature from 900 ℃ to 1 200 ℃,strain rate from 0.001 s-1 to 0.1 s-1 and initial grain size from 48 μm to 230 μm.The hyperbolic constitutive model was established.Based on the hyperbolic constitutive model and dynamic material model,the iso-efficiency map was constructed.Through power dissipation map and microstructure analysis,the deformation temperature and deformation rate duing casting were studied.The results show that the power dissipation rate η J increased with the decrease of strain rate and the increase of temperature when the deformation temperature was not higher than 1 100 ℃,however,changes were opposite when higher than 1 100 ℃.The fine homogenized and completely dynamic recrystallization could be obtained when the η J was not smaller than 0.2.

Influence of CeO_2 on Microstructure and Microhardness of TiC_4 Coating Produced by Laser-Cladding

Abstract: TiC4 ceramic layer modified by CeO2 was deposited on 45 steel substrate by laser-cladding technique.The phase composition,microstructure and microhardness of the clad coating were analyzed by SEM,XRD and micro-hardness tester.The results show that the TiC4 ceramic coating prepared by laser-cladding method had typical surrounding phase and hard spot phase structure.Density of the coating was improved,TiC4 particle size was less than 1 μm and the average micro-hardness increased to 700 MPa when 0.3wt%-1.0wt% CeO2 was added.Adding exccess(≥1.5wt%) CeO2 would make adverse effect on the coating micro-hardness,i.e.,the surrounding phase content and TiC4 particle size increased,and the TiC4 grain was lance-shaped and the micro-hardness decrased to 450 MPa.

Effect of N_2 Flow Rate on Structure and Property of CrN Coatings Deposited by DC Reactive Magnetron Sputtering

Abstract: Chromium nitride(CrN) coating was deposited by DC reactive magnetron sputtering.The effect of N_2 flow rate on microstructure,surface morphology,hardness and bonding force of the CrN coating was studied. The results show that when N_2 flow rate changed from 30%to 100%,the coating was mainly composed of CrN phase.With the increase of N_2 flow rate the grain shape of CrN coatings changed from pyramidal to the coexistence pyramidal and spheroidal topography,and the coatings became denser,which led to the improvement of the hardness.The effect of N_2 flow rate on bonding force of the coating was weak.

Microstructure and Properties Comparison of Laser Cladding Layer and Spraying Layer of Ni-Based Self-Fluxing Alloy

Abstract: The surface morphology,microstructure,micro-hardness and corrosion resistance of the laser cladding layer and spraying layer of the Ni60 Ni-based self-fluxing alloy were analyzed and compared.The results show that the surface forming performance of the laser cladding layer was better than that of the spraying layer.The microstructure of the laser cladding layer was mostly in non-equilibrium and sub-crystalline state,and had a strong and tough two-phase microstructure characteristics.The microstructure of the spraying layer was rich in the hard phase of carbides.Both the laser cladding layer and the spraying layer could get a metallurgy bonding with the substrate.Although the average micro-hardness of the spraying layer was higher than that of the laser cladding layer,its distribution was not uniform.And the corrosion resistance of the laser cladding layer was superior to that of the spraying layer.

Research Progress of Property and Its Application of Aluminium Alloy Auto Sheet

Abstract: Seven property demands for aluminum alloy auto sheet are systematically summarized and proposed,which could make the project of research and developing about aluminum alloy auto sheet have a obvious target.Typical chemical composition,mechanical properties and formability of aluminum alloy auto sheets are introduced.The main factors effected the properties are demonstrated.The pre-treatment technology and its importance to guarantee the performance of the auto sheet are deeply discussed.The important research contents about the sheet are pointed out and the application is described.Reducing cost and price of the sheet and deeply developing application study are important work for expending application of aluminum alloy sheets.

Microstructure and Properties of Low Cost 780 MPa Hot-Rolled High-Strength Steel

Abstract: The 780 MPa high-strength steels were prepared by thermo-mechanical control process(TMCP) on hot tandem mill.The microstructure and properties of the steels were investigated by means of optical microscope, transmission electron microscope and tensile test machine.The results show that the microstructure of the tested steel was mainly composed of fine-grained ferrite and carbides distributed along the ferrite grain boundaries.The yield strength and tensile strength of the steel were about 730 and 790 MPa,and the strain hardening exponent and plastic strain ratio were 0.12 and 0.85,respectively,providing well-matched strength with toughness.The finegrained ferrite and tiny(Nb,Ti)(C,N) precipitates played an effective role in strengthening the steel.

Microstructure and Mechanical Properties of AZ91 Alloy Composites Reinforced with Ni-Coated Carbon Nanotubes

Abstract: AZ91 alloy composites reinforced with nickel coated carbon nanotubes(Ni-CNTs) were fabricated by stirring casting technology.The effects of carbon nanotubes on the mechanical properties and microstructure of the composites were studied,and the fractographs were observed and analyzed by scanning electron microscopy and energy spectrum analysis.The results show that the nickel coated CNTs could refine grain size of the matrix alloy and strengthen mechanical properties of the AZ91 magnesium alloy.Compared with the matrix alloy,tensile strength,elastic modulus and microhardness of the composites had been enhanced significantly with proper adding.The elongation and tensile strength were increased by 90.44% and 37.5% respectively.But with the excessive addition of Ni-CNTs,the Ni-CNTs would segragate,and mechanical properties of the composites were reduced.

Failure Analysis on Fracture of 30CrMnSiNi2A Steel Bolt Used for Wing Cover Plate

Abstract: Failure analysis on a 30CrMnSiNi2A steel bolt used for a wing cover plate which fractured huring storage after assembly was carried out by macro and micro observation of the fracture surface,microstructure inspection and hydrogen content test.The improvement measure was introduced.The results show that the failure mode of the bolt was hydrogen brittle fracture.The reason of hydrogen brittle fracture was the over-high material strength and hydrogen content.Decreasing the strength of the bolt to a proper level was a valid measure to prevent and control hydrogen brittle fracture of the high strength bolts based on the standard dehydrogenation process.

Constitutive Model of Dynamic Softening Behavior of 7075 Aluminum Alloy during Hot Compression

Abstract: Hot compression tests of 7075 aluminum alloy were performed on Gleeble-1500 thermal simulater at strain rate of 001-10 s-1and deformation temperature of 250-450 ℃The true stress-true strain curves during the deformation process were obtainedThe constitutive model of the alloy during deformation at high temperatures was obtained through fitting regression and the strain behavior was predictedThe results show that the simulation results of the Fields-Backofen constitutive model agreed well with the test values before the peak value of the flow stress,while the predicted values of the model which contained a softening factor were closer to the test values

Research Progress on Preparation Technology of Tritium Penetration Barrier on Special -Shaped Pieces of Stainless Steel

Abstract: Preparation of tritium penetration barrier(TPB) with high performance on stainless steel specialshaped pieces is a key technology in its engineering application.The types and properties of the tritium penetration barrier are reviewed,and the research progress on preparation technology of the barrier on special-shaped pieces of stainless steel and its advantages and disadvantages are described.Aiming at the preparation of FeAl/Al_2O_3 composite tritium penetration barrier with high chemical stability and dense structure,two new technologies,metal organic chemical vapor deposition and electroplating from ambient temperature molten salt,are put forward.

Homogenizing Annealing of 3104 Aluminum Alloy

Abstract: The microstructure of as-casted and homogenizing annealing with different parameters 3104 aluminum alloy were studied by means of thermal analysis and optical microscope,then homogenization annealing parameters were determined.The morphology and types of main compounds were studied by scanning electron microscope and its accessory.The results show that the reasonable homogenizing annealing parameters was 590 ℃ for 12 h,and various compounds appeared due to the difference of main alloy components after homogenizing annealing which mainly consisting of(FeMn)Al6,MnAl6,(Al,Fe,Mn,Si) quaternary phase,Mg2Si phase,(Al,Mn,Si) ternary phase,Al8Mg5,(Al,Mn,Mg,Fe) quaternary phase and so on.

Wettability of Human Blood on Titanium Alloy Surface with Different Compositions and Roughnesses

Abstract: The contact angle(θ) of different HCT bloods on three titanium alloys(TA2,TC4,TLM) surfaces which had different roughnesses was studied using JY-82 contact angle meterThe wettability of the human blood on the titanium alloy surface was investigatedThe results show that the rougher the alloy surface,the better the wettability of the blood on the surface under the test conditionsThe bigger the blood's HCT,the worse the wettability on the alloy surfaceThe wettability of the blood on the TLM alloy was the best,the TA2 titanium alloy was the worst,and the TC4 alloy was moderate

Effect of Brazing Clearance on Microstructure and Hardness of Vacuum Brazing Joint of 316L Stainless Steel

Abstract: Vacuum brazing of 316L stainless steel with BNi-2+40%BNi-5 nickel-based mixed filler metal was carried out to obtain the joints with 3 kinds of brazing clearances.Microstructure of solder joints,element distribution and microhardness of the joints were studied by means of optical microscopy,scanning electron microscopy,energy dispersive X-ray spectroscopy and microhardness testing.The results show that the joints were composed of solid solutions continuous,eutectic compounds and meshwork compounds.The amounts of intermetallic compounds decreased,the joint composition and hardness distribution were more uniform with the decrease of brazing clearance.Continuous microstructure of the joint with 30 μm brazing clearance was mainly solid solution,and the comprehensive properties were the best.

Discontinuous Precipitation and Recrystallization Behavior of Pb-Ca-Sn-Al Alloy during Aged Process after Solid-Solution Treatment

Abstract: The discontinuous precipitation(DP) and recrystallization behavior of the Pb-0.05%Ca-1.5%Sn-0.026%Al(mass fraction) alloy during aged at 100 ℃ after solid-solution by different processes were analyzed by means of optical microscope,scanning electron microscope,X-ray energy dispersion spectroscope and micro hardness tester.The results show that all the grain size of the alloy after solid-solution by different processes was about 1 000 μm.After aged at 100 ℃,the grain size of the alloy aged for 35 h was refined to 300-400 μm after solid-solution at 270 ℃ for 30 min cooled in air and heated at 310 ℃ for 30 min cooled in water(process A),while the grain size of the alloy aged for 12 h was refined to 60 μm after solid-solution at 270 ℃ for 30 min cooled in water(process B).The grain refinement was due to the nucleation and growth of DP,and the recrystallization could be achieved without plasticity deformation.The holding time for the discontinuous precipitation during aged process of the alloy and the grain refinement were different with various solid-solution processes.With the prolongation of the holding time,there were two peak values on the hardness curves of the alloy treated by process A,the secondary hardening phase was(PbSn)3Ca.The hardness curves of the process B had no rule to follow,and the fine-grained microstructure was unstable.

Effect of Rare Earth Y on Microstructure and Tensile Properties of A356 Alloy

Abstract: The effect of rare earth Y on the microstructure and tensile properties of A356 alloy was studied by using OM,SEM and tensile testing machine.The results indicate that rare earth Y is an excellent modifier for A356 alloy.Y could not only refine primary α-Al phase,make the grain fine and equiaxed,reduce secondary dendrite arm spacing,but also could result in the transformation from striation texture to fibrous eutectic Si.When 0.4wt% Y was added,the values of the tensile strength σb and elongation δ of A356 alloy reached 298 MPa and 9.5%,which were increased by 29.6% and 21.5% respectively,compared with the alloy without adding Y element.

Influence of Coiling Temperature on Microstructure and Properties of X80 Pipeline Steel

Abstract: X80 pipeline steel plate was prepared by controlled rolling and controlled cooling method using a  450 mm laboratory rolling mill.The influence of coiling temperature on the microstructure and mechanical properties of the steel was investigated by means of optical microscope,TEM and mechanical property tester.The results show that when the coiling temperature increased from 463 ℃ to 597 ℃,the content of acicular ferrile(AF) in X80 pipeline steel increased,and the M-A island became finer and well-proportioned.When the coiling temperature was 597 ℃,the yield strength and tensile strength of X80 pipeline steel could be 650 MPa and 790 MPa respectively,and the elongation was about 30%.

Research Progress on Pipeline Steel Used for Oil and Gas Transmission in Acid Environment

Abstract: The oil and gas fields which containing H2S have been rapidly developed,thus the development of pipeline steel used for oil and gas transmission in acid environment is imperativeThe research progress of the pipeline steel used for oil and gas transmission is reviewed from the mechanism of the H2S corrosion and the influencing factors under the service condition in acid environmentAt the same time the current development of the acid corrosioin resistance steel pipe used for the oil and gas transmission at home and abroad is introducedThe sulfide stress corrosion cracking(SSCC) resistance study of the pipeline steel is pointed out and the related standards should be further investigated

Influence of Modification on Microstructure and Mechanical Properties of Hypereutectic Al-Si Alloy

Abstract: The A390 hypereutectic Al-Si alloy with 18wt% Si content was prepared through the melt modified by binary and ternary modifiers during the casting process.The influence of modification on microstructure and mechanical properties of A390 hypereutectic Al-Si alloy was investigated by optical microscopy analysis,scanning electron microscopy observation,wear resistance test and tensile strength test.The results show that after the modification of A390 alloy,the corner angle of the primary Si was inactivated,and its size was below 30 μm.Eutectic Si was spheroidized,and the grain was refined.Mechanical properties of the modified alloy were improved apparently.After ternary modification,compared to non-modification,the elongation and tensile strength of A390 alloy at room temperature had been increased by 150% and 31%,respectively.Wear resistance of the A390 alloy was also improved.The wear resistance in ternary modification was mainly microscopic cutting.

Reason of 20SiMn2MoVA Steel with Low Impact Property

Abstract: The reason why the 20SiMn2MoVA steel with low impact toughness was analyzed by using OM, SEM,TEM and EPMA.The improvement was pointed out The results show that chemical composition had element spot segregation,non martensite microstructure generated and carbide precipitated which resulted in low impact toughness of 20SiMn2MoVA steel after quenching and low temperature tempering.Increase the quenching temperature and cooling speed properly will benefit to decrease the amount of the non martensite and increase the impact toughness.

Damping Properties of Macroscopic Graphite Particulate Reinforced Commercially Pure Aluminum Matrix Composites

Abstract: Macroscopic graphite particulate reinforced commercially pure aluminum matrix composites were prepared by air pressurization seepage technique.The internal friction(damping properties) and relative dynamic modulus were tested in the temperature range of 25-400 ℃ at low frequencies and strain amplitudes by using multifunction internal friction apparatus.The microstructure of the composites was observed by means of transmission electron microscope.The results show that little micro pores were found on the interface of the composites,and the bonding between the particles and the matrix was weak.With the increase of the graphite particulate volume fraction the damping properties of the composites with same graphite particles grain size increased.With the increase of the graphite particulate grain size the damping properties of the composites with same graphite particulate volume fraction increased.Compared with the damping properties of the commercially pure aluminum,the damping properties of the composites increased 2-3 times.The main damping mechanisms for the composites were the interface damping and dislocation damping.

Grain Growth Behavior of Mn18Cr18N Retaining Ring Steel during Multi-heating Hot Forging Process

Abstract: In order to solve the problem of grain growth for the Mn18Cr18N retaining ring steel during the multi-heating hot forging process,the effect of heating condition on grain size was investigated.The two-heating forging test had also been verified with small samples.The results show that the grain size of forgings had a certain hereditary,and the grain size didn't dramatically grow when the forging reheated at 1 100℃for less than 5 h or 1 050℃for longer time.And the grain growth mode of the steel was D_t~(5.9)-D_0~(5.9) =2.2×10~(26)exp((-486 809)/(RT))·t.

Effects of pH Value and Concentration of Solution on P Content and Deposition Rate during Electroless Ni-P Plating on Aluminum Substrate Surface

Abstract: The effects of the factors including pH value,concentration of main salt,reductant and complexing agent of the solution on the deposition rate and P content of the electroless Ni-P plating on aluminum substrate surface were investigated by the orthogonal test The results show that the effect of the solution pH value was the most significant,and it was followed by main salt concentration and reductant concentration.In the selected acid solution,with the increase of pH value in the range of 3.5 to 6.0,the P content in the solution decreased from 22.5at%(pH=3.5) to 12.6at%(pH=6.0).And the deposition rate increased till the rate reached the maximum value of 21.0μm·h~(-1)(pH=5.0),and then it had little change.The P content decreased with the increase of main salt concentration of NiSO_4,but increased with the increase of reductant concentration of NaH_2 PO_2.The deposition rate increased with the increase of the concentration of main salt and reductant An excellent Ni-P plating with 15.2at%P and deposition rate of 21.0μm·h~(-1) could be obtained.

Hot Deformation Behavior and Processing Maps of AZ31 Magnesium Alloy

Abstract: The hot deformation behavior of AZ31 magnesium alloy was investigated by thermo-compression tests with Gleeble-1500D thermal simulatorThe tests were performed in the temperature range from 473 to 723 K and at strain rates from 0001 to 1 s~(-1)The steady flow stress was described by the hyperbolic sine constitutive equationThe processing maps were drawn and analyzed according to the dynamic material modelThe results show that the instability zones of flow behavior could also be recognized by the mapsThe optimal processing parameters of hot deformation under the test condition was able to be attained by the maps as follow:hot deformation temperature of 473-523 K and strain rate around 001 s~(-1)The superplastic forming could be performed when the temperature was 623-673 K and strain rate was about 0001-0006 s~(-1)The range of strain rate could be wider when the deformation temperature was higher than 673 K

A Non-quenched and Tempered Bainitic Steel with High Strength-Toughness and Hardenability

Abstract: A non-quenched and tempered bainitic steel with high strength-toughness and hardenability had been developed.The microstructure,mechanical properties and continuous cooling transformation(CCT)curves of the steel were studied,and its strength-toughness was compared with that of the 42CrMo steel.The results show that both the tested steels microstructure cooled at air and sand after forging was bainite and the strength-toughness was similar.The steel had good hardenalility and broad bainitic transformation.The ferrite did not appear as the cooling rate was lower than 0.05℃·s~(-1).The mechanical properties of the bainitic steel were better than those of traditional quenched and tempered steel 42CrMo after tempered at 350℃for 2 h.

Microstructure and Cutting Performance of New Free-Cutting Stainless Steels Used for Ball Point Pen

Abstract: A new type S-Pb ferritic free-cutting stainless steel was manufactured by intermediate frequency furnace and electroslag remelting.The chemical composition,microstructure,inclusion and cutting performance were analyzed by optical microscopy,SEM,EDS and ultra-precision CNC lathe.The results show that the freecutting phases of the tested steel bar,product wire and imported SF20T product wire contained MnS,Pb and the composite inclusion consisted of MnS,Pb and Te.MnS in the steel bar was spindle.MnS in the cold-drawn product wire was fine and elliptical in transverse direction,and distributed along the drawing direction in forms of chain and intermittence,with the size smaller than the transverse and lognitudinal size in SF20T product wire.The matrix microstructure of the tested steel product wire was ferrite with the grain size scale of 10.The cutting performance of the steels was good at high-speed and medium feeding rate,this could meet the requirements to the chip morphology and surface roughness.