Laser cladding of titanium alloy coating on titanium aluminide alloy substrate

1　INTRODUCTIONInthedesignandmanufactureofaviationindus try ,differentpartsoftheaircraftengineshouldmeetthedifferentrequirementsonoperatingtemperatureandserviceperformance .Thesoundbondofdissimi laralloysisthekeytechniquefordevelopingnovele quipmentsandimprovingtheirintegralperformance .Lowdensityandexcellenthigh temperaturepropertiesofTiAlalloysmakethem promisinghigh temperaturestructuralmaterials .Successfuljoiningofthesematerialswillincreasetheirutilityinengineer ing[1,2 ] .Somejoinin…     

Electropolishing parameters of NiTi alloy

Electropolishing has been used in NiTi alloy in several fields for its special characteristics, but its essential details and electropolishing mechanism have not been reported yet as a demand from business competition, which, to a great degree, restricts the application and extension of the electropolishing technology. The effect of processing parameters on nitinol electropolishing was explored. Besides the electrolyte, other factors that influence the electropolishing are temperature, current density, time, spacing between anode and cathode, electrolyte stirring, etc. Studies on the effect of the temperature on the electropolishing process show that the higher the temperature is, the bigger the electropolishing rate is, following the near Gauss law. The relationship between the temperature and the surface roughness follows a near parabolic law, and the relationship between the temperature and the surface reflectivity follows a near sigmoidal law. The relationship between the electropolishing voltage and the current density follows a near cubic law, while that between the electropolishing rate and current density follows a near linear law. The relationship between the electropolishing rate and the time follows a near sigmoidal law. The practical spacing between anode and cathode is confirmed by the Hall bath experiment.     

Properties of Zr-Ti-V-Mn-Ni hydride alloy

1　ＩＮＴＲＯＤＵＣＴＩＯＮＷｉｔｈｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｅｃｏｎｏｍｉｃｓａｎｄｃｉｔｙｔｒａｆｆｉｃｓ ,ｍｏｒｅａｎｄｍｏｒｅｏｉｌ ｐｏｗｅｒｅｄｖｅｈｉｃｌｅｓａｐｐｅａｒ,ｒｅｓｕｌｔｉｎｇｍｏｒｅｓｅｒｉｏｕｓｐｏｌｌｕｔｉｏｎｔｏｔｈ     

Thermal stability of Al-Mg-Sc-Zr alloy

The thermal stability of Al3（Sc,Zr） precipitates in the cold worked Al-Mg-Sc-Zr alloy after elevated temperature exposure was investigated. The evaluation was conducted using room temperature tensile, Vicker＇s hardness, optical metallography and scanning electron microscope （SEM） with the backscatter. The results show that the Al3（Sc,Zr） precipitates and mechanical properties have no obvious change, and the grains keep elongated along the working direction as that in cold worked sample after exposure at 300℃ for 1 000 h. The coarsening of Al3（Sc,Zr） precipitates occurs and is no longer effective on the recrystallization resistance, and partial recrystallization is observed after 400℃ exposure. In particular, after 500℃ exposure, the hardness decreases drastically and the alloy has fully recrystallized due to the obvious coarsening of Al3（Sc,Zr） precipitates.     

Calorimetric study of Wood alloy

1　ＩＮＴＲＯＤＵＣＴＩＯＮＷｏｏｄａｌｌｏｙｂａｓｅｄｏｎｍａｔｒｉｘｏｆｂｉｓｍｕｔｈｍｅｔａｌｉｓａｋｉｎｄｏｆａｌｌｏｙｐｏｓｓｅｓｓｉｎｇｌｏｗｍｅｌｔｉｎｇｐｏｉｎｔｓａｎｄｌｉｔｔｌｅｒｉｇｉｄｉｔｙ .Ｉｔｓｔｅｎｓｉｌｅｓｔｒｅｓｓｉｓａｌｓｏｖｅｒｙｌｉｍｉｔｅｄ .Ｕｓｕａｌ ｌｙ ,ｉｔｉｓｕｓｅｄａｓｔｅｍｐｅｒａｔｕｒｅｃｏｎｔｒｏｌｌｉｎｇｍａｔｅｒｉａｌｓｔｏｐｒｏｔｅｃｔｅｌｅｃｔｒｉｃａｎｄｓｔｅａｍｅｑｕｉｐｍｅｎｔ,ｓｕｃｈａｓ,ｂｌｏｗｎｆｕｓｅｓａｎｄｅｕｔｅｘ…     

Preparation of Al–La master alloy by ultrasonic method and modification on Al alloy

In this study, two kinds of Al–La master alloys were prepared by ultrasonic method and ordinary mixmelting method, and both of the alloys were added into the Al alloy.Then, the microstructure of Al–La master alloy and the modification effect on the Al alloy were investigated using optical microscope(OM), X-ray diffraction(XRD), scanning electron microscope(SEM), and energy disperse spectroscopy(EDS).The results show that because of ultrasonic cavitation and streaming, the grain size of Al–La master alloy prepared by the ultrasonic method is refined, which distributes evenly.And, there is no gas hole,inclusion, or segregation in the Al–La master alloy with aAl, La, and La3Al11.Furthermore, Al–La master alloys show a nice modification for Al alloy, which is much better than that prepared by ordinary mix-melting method.     

Grain refinement of hypoeutectic Al-Si alloy prepared with ELTA by Al-4B master alloy

Electrolytic low-titanium aluminum （ELTA） was produced by adding TiO2 powder to an industrial aluminum electrolyzer. The grain refining effect of Al-4B master alloy in the hypoeutectic Al-Si alloy prepared by using ELTA was investigated, and compared with those of Al-STi, Al-STi-IB and Al-4B master alloys in the similar alloy prepared by using pure Al. The results indicate that when Al-4B is added to the melt of the alloy prepared by using ELTA in terms of the Ti/B mass ratio of S：l, the grain refining effect is better than those ofAl-STi, Al-STi-IB and Al-4B master alloys. Thus, using Al-4B to refine the grain of Al-Si alloys prepared by using ELTA will possibly become a feasible way of obtaining Al-Si alloy with homogeneous and fine microstructure.     

Single-aging characteristics of 7055 aluminum alloy

The microstructures and properties of 7055 aluminum alloy were studied at different single-aging for up to 48 h using hardness test, tensile test, electrical conductivity measurement, XRD and TEM microstructure analysis. The results show that at the early stage of aging, the hardness and strength of the alloy increase rapidly, the peak hardness and strength are approached after 120 ℃ aging for 4 h, then maintained at a high level for a long time. The suitable single-aging treatment of 7055 alloy is 480 ℃, 1 h solution treatment and water quenching, then aging at 120 ℃ for 24 h. Under those condition, the tensile strength, yield strength, elongation and electrical conductivity of the studied alloy are 513 MPa, 462 MPa, 9.5% and 29%（IACS）, respectively. During aging, the solid solution decomposes and precipitation occurs. At the early aging stage of 120 ℃, GP zones form and then grow up gradually with increasing ageing time. η′ phase forms after ageing for 4 h and η phase starts to occur after 24 h aging.     

Microstructure of Ag-Sn-Cu-Bi-Ni alloy after oxidation

Ag-Sn-Cu-Bi-Ni alloy was internally oxidized in air. The phase constitution, surface morphology and microstructure evolution of the alloy after internal oxidation were analyzed by X-ray diffractometry, optical microscopy and scanning electron microscopy, respectively. The results show that the surface color of samples after internal oxidation is different from the different oxidation time and temperatures. The oxidation reaction firstly takes place on the grain boundaries. The microstructure developed on the initial stage of internal oxidation is fir-tree crystal texture. However, this texture structure disappears accompanied by grain growth and oxides forming during the prolonged oxidation. Finally, the oxide particles are uniformly dispersed in the silver matrix.     

Superplastic behavior of Al-Cu-Li based alloy

The superplastic behavior was studied in an Al-4Cu-ILi-0.4Mg-0.4Ag-0.1Zr alloy. The alloys were manufactured both by＂ a conventional rolling route and a thermo-mechanical treatment route. The superplastic properties were evaluated as a function of temperature, strain rate, and processing history. Prior to thermo-mechanical processing, the alloys have elevated-temperature ductilities of 94% to 130%, strain rate sensitivities of about 0.25, and activation energies corresponding to lattice diffusion. After thermo-mechanical processing, the alloys have ductilities of 200% to 630%, strain rate sensitivity of about 0.42, and activation energies corresponding to grain boundary diffusion or a mixture of grain boundary diffusion and lattice diffusion. Skipping rapid recrystallization annealing can supply a higher value of elongation-to-failure.     

Preparation of Ti-based amorphous brazing alloy

A new kind of amorphous active brazing alloy foil with the composition of Ti40Zr25Ni15Cu20 was successfully synthesized using melt spinning in roll forging machine in argon atmosphere. The amorphous structure and composition were examined by X-ray diffraction, differential thermal analysis and energy dispersive X-ray detector. The results show that the Ti40Zr25Ni15Cu20 amorphous alloy foil has excellent wettability on Si3N4 ceramic and demonstrate a strong glass forming ability. The reduced glass transition temperature （Trg） and the temperature interval of supercooled liquid region before crystallization are 0.76 and 78 K, respectively.     

Electroplating process of amorphous Fe-Ni-Cr alloy

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅａｍｏｒｐｈｏｕｓａｌｌｏｙｓａｒｅａｎｅｗｋｉｎｄｏｆｍａｔｅｒｉ ａｌｓｗｉｔｈｓｈｏｒｔ ｒａｎｇｅｏｒｄｅｒａｎｄｌｏｎｇ ｒａｎｇｅｄｉｓｏｒｄｅｒ .Ｔｈｅｙｄｉｓｐｌａｙｍａｃｒｏｓｃｏｐｉｃｕｎｉｆｏｒｍｉｔｙａｎｄｉｓｏｔｒｏｐｙ .Ｂｅｃａｕｓｅｏｆｔｈｅｉｒｅｘｃｅｌｌｅｎｔｐｈｙｓｉｃａｌ,ｃｈｅｍｉｃａｌａｎｄｍｅ ｃｈａｎｉｃａｌｐｒｏｐｅｒｔｉｅｓ ,ｔｈｅｒｅｓｅａｒｃｈａｎｄｄｅｖｅｌｏｐｍｅｎｔｏｆｔｈｅａｍｏｒｐｈｏｕｓａｌｌｏｙｓｂｅ…     

Diffusion bonding of γ-TiAl alloy to Ti-6Al-4V alloy under hot pressure

1 Introduction Alloys based on the ?-TiAl intermetallic compounds have been of much interest in recent years as light-mass structural materials for elevated temperature aerospace applications[1- 5]. Successful joining and cost effective fabrication method…     

Defect analysis of complex-shape aluminum alloy forging

The isothermal precision forging was applied for the purpose of forming aluminum alloy with complex shape. The complexity of forging is easy to lead to the occurrence of the defects, such as underfilling, folding, metal flow lines disturbance and fibre breaking. The reasons for the defects were analyzed on the basis of experiments and finite element method（FEM）. The results show that the size of flash gutter bridge, the lubricating condition and the deformation process are the main factors influencing the filling qualities of complex-shape aluminum alloy forging. The folding defect is mainly caused by different velocities of filling cavities, fast flow of much metal in one direction and confluence of two or multi metal strands. Improper metal distribution in different regions can cause the flow lines ＂disturbance and fast metal flow in one direction is also a cause of the flow lines disturbance According to the reasons, some measures were taken to improve the quality of the forged parts.These studies can contribute to offering some experiences in making process project and optimizing the process parameters for forging complex-shape aviation products.     

Shear bands in magnesium alloy AZ31

During deformation of magnesium at low temperatures, cracks always develop at shear bands. The origin of the shear bands is the { 1011 } twinning in basal-oriented grains and the mobility of this type of twin boundary is rather low. The most frequent deformation mechanisms in magnesium at low temperature are basal slip and { 1012 } twinning, all leading to the basal texture and therefore the formation of shear bands with subsequent fracture. The investigation on the influences of initial textures and grain sizes reveals that a strong prismatic initial texture of (0001) parallels to TD and fine grains of less than 5 8m can restrict the formation and expansion of shear bands effectively and therefore improve the mechanical properties and formability of magnesium.     

Properties of electrodeposited amorphous Fe-Ni-W alloy deposits

1Introduction Chromium electrodeposition is a widely applied technique in industries for the production of decorative and functional coatings.That is because it possesses attractive properties such as decorative appearance,high hardness,and excellent wear…     

Interaction between γ-TiAl alloy and zirconia

A study on the interaction between TiAl alloy and zirconia was carried out in argon atmosphere. The micrographic observations of the cross-section perpendicular to the interface were obtained using a scanning electron microscope with a dedicated energy dispersive spectrometer （SEM/EDS）. The results showed that firstly TiAl alloy spreads on the ceramic surface, and then infiltrates into the pores between ceramic particles accompanied by a chemical reaction. The whole ceramic mold is broken into tiny blocks. A multiple fission reaction mechanism was developed to explain the interaction between TiAl alloy and zirconia.     

Amorphous in a Zr-IQC-DQC pseudo-ternary alloy system

A pseudo-ternary alloy system was constructed by combining an icosahedral quasicrystal (IQC), a decagonal quasicrystal(DQC), and Zr into one alloy system. Different proportions of Zr were added to pseudo-binary alloy IQC80DQC20 (mass fraction in %). Structural evolution in these alloys was discussed. An amorphous alloy composition was found in this system and a melt-spinning amorphous alloy was produced in this composition. Through DSC analysis, the amorphous alloy exhibits high glass forming ability comparable to that of the Inoue Zr65Al75Cu17.5Ni10 amorphous alloy.