A review on advances of high-throughput experimental technology for titanium alloys

Ti alloys,as leading lightweight and high-strength metallic materials,exhibit significant application potential in aerospace,marine engineering,biomedical,and other industries.However,the lack of fundamental understanding of the microstructure−property relationship results in prolonged research and development(R&D)cycles,hindering the optimization of the performance of Ti alloys.Recently,the advent of high-throughput experimental(HTE)technology has shown promise in facilitating the efficient and demand-driven development of next-generation Ti alloys.This work reviews the latest advancements in HTE technology for Ti alloys.The high-throughput preparation(HTP)techniques commonly used in the fabrication of Ti alloys are addressed,including diffusion multiple,additive manufacturing(AM),vapor deposition and others.The current applications of high-throughput characterization(HTC)techniques in Ti alloys are shown.Finally,the research achievements in HTE technology for Ti alloys are summarized and the challenges faced in their industrial application are discussed.

Creep properties of bimetal Al/SiC/Cu compositesfabricated via accumulative roll bonding process

In the present study,microstructural evolution,mechanical and creep properties of Al/SiC/Cu composite stripsfabricated via accumulative roll bonding(ARB)process were studied.The obtained results showed the formation of anatomic diffusion layer with thickness of about 17μm at the interface during the ARB under three creep loadingconditions namely 30 MPa at 225℃,35 MPa at 225℃,and 35 MPa at 275℃.An generated intermetallic compoundresulted in a 40%increase of interface thickness near Al.The stress level decreased by 13%at constant temperature withno signi fi cant effect on the interface thickness,and the creep failure time declined by 44%.It was observed that atconstant temperatures,the second slope of the creep curve reached to 39%with increasing stress level,then,it dropped to2%with a little temperature rising.After creep test under 35 MPa at 275℃,the sample displays the presence of 60%Aland 40%Cu,containing brittle Al_(2)Cu intermetallic compound at the interface.Applied temperature and stress had effecton the creep properties,specially increasing the slope of creep curves with higher stresses.

Microstructure and formation process of Ni-pool defect in WC-8Ni cemented carbides

The morphologies and formation process of Ni-pool defects in WC?8Ni cemented carbides were studied. The SEM images show that Ni-pool generally has two kinds of morphologies: “island” in isolation and “ring” around a new phase. In the obtained samples with “ring-like Ni-pool”, WC, Ni and Ni2W4C (η phase) phases were detected in XRD patterns. Combined with SEM, EDX and XRD results, it is found that the phase in the center of the “ring-like Ni-pool” is Ni2W4C (η phase) and the main chemical components of Ni-pool are Ni, W and C. In addition, the relationships among large size Ni (agglomerated) particles, volatile impurities, pores and carbon content vs forming process of the Ni-pool defects for WC?8Ni cemented carbides are also presented and discussed.

Preparation of micro-nanostructure on titanium implants and its bioactivity

Surface modification of medical implants was considered as an effective method to improve the cellular behaviors and the integration of tissue onto materials. The micro-nanostructured surface on the titanium alloy was prepared by laser treatment and multiple acid etching. The surface morphologies of different titanium alloy substrates were characterized by scanning electron microscopy (SEM). The effects of micro-nanostructured surfaces on the cellular responses were investigated in vitro by observing hydroxyapatite formation, cell morphology and cell adhesion. The results indicate that the micro-sized structure promoted the adhesion and proliferation of cultured osteoblasts. Furthermore, the micro-nanostructured surface was more conducive to cell adhension stretching compared with the micro-structured surface. All results suggest that the micro-nanostructured surface improved the biocompatibility and integration of tissue onto titanium alloy implants.

Structure and properties of FeCoNiCrCu_(0.5)Al_x high-entropy alloy

Effects of Al content and heat treatment on the structure,hardness and electrochemical properties of FeCoNiCrCu0.5Alx high-entropy alloys were investigated.The phase structure of as-cast alloys evolves from FCC phase to BCC phase with the increase of Al content.The stable phase of FeCoNiCrCu0.5Alx high-entropy alloys will transform from FCC phase to FCC＋BCC duplex phases when x value increases from 0.5 to 1.5.The hardness of BCC phase is higher than that of FCC phase,and the corrosion resistance of BCC phase is better than FCC phase in chlorine ion and acid medium.High hardness and good corrosion resistance can be obtained in as-cast FeCoNiCrCu0.5Al1.0 alloy.

Roles of Zr and Y in cast microstructure of M951 nickel-based superalloy

The influence of Zr and Y on the cast microstructure of a nickel-based superalloy was investigated by optical microscopy （OM）,scanning electron microscopy（SEM）,electron probe micro-analysis（EPMA）and X-ray diffraction（XRD）.Theγ＋γ′eutectic volume in the superalloy rises notably with the increase of Zr or Y content.Meanwhile,the morphologies of primary MC carbides change from needle and platelet-like to blocky shape with increasing Zr and Y doped.The XRD results show that the primary MC carbide lattice constant increases with Zr and Y additions,and EPMA investigation shows that the platelet-like MC carbides contain primarily Nb and C,while those carbides in blocky shape have 39.2%Zr and 39.6%Nb in average,.These influences on the cast microstructure can be attributed to the atomic size effects of Zr and Y.

Failure mechanism of as-cast Mg-6Zn-2Er alloy during tensile test at room temperature

Tensile test of the as-cast Mg-6Zn-2Er alloy was conducted at room temperature. The results indicate that the alloy is inclined to failure when the strain reaches 5.6%. The coarse secondary phases are responsible for the failure, especially for the Mg3Zn3Er2 phase （W-phase）. It is indicated that the existence of the W-phase activates the stress concentrations due to the incapacity of W-phase for the load transfer, which results in the void at the inner of the W-phase. In comparison, the interface between the matrix and the secondary phase is stable. In conclusion, the characters of the secondary phases with respect to size, distribution, morphology and type, play an important role in the plastic deformation behavior of the alloy.

Phase-field study on competition precipitation process of Ni-Al-V alloy

With microscopic phase-field kinetic model, atomic-scale computer simulation program for the precipitation sequence and microstructure evolution of the ordered intermetallic compound γ＇ and θ in ternary Ni75AlxV25-x alloy were studied. The simulation results show that Al concentration has important effects on the precipitation sequence. When Al concentration in Ni75AlxV25-x alloy is low, 0（Ni3V） ordered phase will be firstly precipitated, followed by γ＇（Ni3Al） ordered phase. With Al concentration increasing, θ and γ＇ ordered phases are simultaneously precipitated. With A1 concentration further increasing, γ＇ ordered phase is firstly precipitated, followed by θ ordered phase. There is a competition relationship between θ and γ＇ ordered phases during growth and coarsening process. No matter which first precipitates, θ ordered phase always occupies advantage in the competition process of coarsening, thus, the microstructure with preferred orientation is formed.

Structure and hydrogen storage performance of LaNi_(4.25)Al_(0.75) alloy

Hydrogen storage properties of LaN4.25Al0.75 alloy were experimentally investigated by XRD, PC isotherm curves, hydrogen absorption kinetics curves, XPS and its particle diameter. The structure of unit cell of LaNi4.25Al0.75 alloy was deduced. The relationship between its structure and hydrogen storage performance of LaNi4.25Al0.75 alloy was analyzed. The results show that LaNi4.25Al0.75 alloy has rapid hydrogen absorption rate and good resistance to combustibility. It is also found that the function of the hydrogen absorption plateau pressure and temperature is ln peq=-4 820/T＋12.46, and the hydrogen absorption rate of the alloy decreases with increasing the temperature.

Microstructure and tribological behavior of Mg-Gd-Zn-Zr alloy with LPSO structure

A Mg-14.28Gd-2.44Zn-0.54Zr （mass fraction, %） alloy was prepared by conventional ingot metallurgy （I/M）. The microstructure differences in as-cast and solution-treated alloys were investigated. Sliding tribological behaviors of the as-cast and solution-treated alloys were investigated under oil lubricant condition by pin-on-disc configuration. The wear loss and friction coefficients were measured at a load of 40 N and sliding speeds of 30-300 mm/s with a sliding distance of 5000 m at room temperature. The results show that the as-cast alloy is mainly composed ofα-Mg solid solution, the lamellar 14H-type long period stacking ordered （LPSO） structure within matrix, andβ-[（Mg,Zn）3Gd] phase. However, most of theβ-phase transforms to X-phase with 14H-type LPSO structure after solution heat treatment at 773 K for 35 h （T4）. The solution-treated alloy presents low wear-resistance, because the hard β-phase is converted into thermally-stable, ductile and soft X-Mg12GdZn phase with LPSO structure in the alloy.

Effect of heat treatment on microstructure and tensile strength of NiCoCrAl alloy sheet fabricated by EB-PVD

The NiCoCrAl alloy sheet was fabricated by electron beam physical vapor deposition technique and the effects of the heat treatment on the microstructure and tensile strength of the NiCoCrAl alloy sheet were investigated. The heat treatment at 1050 °C is favorable to improve the interface bonding between the columnar structures due to the disappearance of the intergranular gaps. Comparing with the thin NiCoCrAl alloy sheet before heat treatment, the Ni3Al phase appears in the NiCoCrAl alloy sheet after heat treatment, which is favorable to improve the interface bonding between the columnar structures. The increase in the tensile strength and elongation is attributed to the improvement of the interface bonding between the columnar structures. The residual stress in the NiCoCrAl alloy sheet after heat treatment is reduced significantly, which also confirms that the interface bonding is improved by the heat treatment.

Effects of microwave sintering temperature and soaking time on microstructure of WC-8Co

WC-8Co cemented carbide samples were processed via microwave irradiation in a 2.45 GHz, high-power multi-mode microwave cavity. The densification of the compacts and the microstructures of the prepared alloys were studied. The results demonstrate that the liquid phase is formed around 1300 ℃ and nearly full densification is obtained at 1450 ℃ for 5 min via microwave irradiation. The microstructures of microwave sintered samples have finer and more uniform WC grains than those of vacuum sintered samples. Besides, the WC grain size and distribution are only decided by the sintering temperature. Holding time has negligible effects on them. No matter how holding time is, the mean grain size is 2.7 pan when the sintering temperature is kept at 1450 ℃.

Microstructure and properties of rare earth-containing Cu-Cr-Zr alloy

Cu-0.81Cr-0.12Zr-0.05La-0.05Y(mass fraction) alloy was successively subjected to hot rolling, solid solution treatment, cold rolling and aging treatments. Its microstructure, microhardness and electrical conductivity at different states were systematically investigated. The as-cast microstructure consists of three phases: Cu matrix, Cr and Cu5 Zr. Zr is completely dissolved into the matrix while partial Cr remains after the solid solution treatment. Aging of the cold-rolled sample makes nanocrystals of Cr and Cu5 Zr precipitate from the matrix, and the microhardness and electrical conductivity rise. A combination of high microhardness(HV 186) and high conductivity(81% IACS) can be obtained by aging the sample at 773 K for 60 min. As the aging temperature increases, the orientation degree of the Cu crystals gradually decreases to zero, but the microstrain in them cannot be eliminated completely owing to the presence of precipitates and dislocations. The Cr precipitates exhibit the N-W orientation relationship with the matrix when the coherence strengthening mechanism plays a main role.

Microstructure and shear strength of reactive brazing joints of TiAl/Ni-based alloy

Reactive brazing of TiAl-based intermetallics and Ni-based alloy with Ti foil as interlayer was investigated. The interfacial microstructure and shear strength of the joints were studied. According to the experimental observations, the molten interlayer reacts vigorously with base metals, forming several continuous reaction layers. The typical interfacial microstructure of the joint can be expressed as GH99/（Ni,Cr）ss（γ）/TiNi（β2）＋TiNi2Al（τ4）＋Ti2Ni（δ）/δ＋Ti3Al（α2）＋Al3NiTi2（τ3）/α2＋τ3/TiAl. The maximum shear strength is 258 MPa for the specimen brazed at 1000°C for 10 min. Higher brazing temperature or longer brazing time causes coarsening of the phases in the brazing seam and formation of brittle intermetallic layer, which greatly depresses the shear strength of the joints.

Microstructure characterization on Mg-2Nd-4Zn-1Zr alloy duringheat treatment

The microstructures of Mg-2Nd-4Zn-1Zr alloy in the as-cast state and after heat treatment were investigated. Several kinds of secondary phases were found and characterized by transmission electron microscopy （TEM）, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. In the as-cast alloy, the existing eutectic compounds are Mg-Nd-Zn ternary phases： T phases and W phases. After the heat treatment, with increasing the temperature or time, it was found that T phase almost dissolved into the α-Mg matrix, while a large amount of W phase remained in the matrix. On the other hand, with prolonging the time, the morphology of the phase changed from continuous network to the spherical shape along the grain boundary. The density of the W phase gradually decreased and finally it was coarsened and stabilized in the treatment process.

Influence of nano-SiC on microstructure and property of MAO coating formed on AZ91D magnesium alloy

Ceramic coating incorporated with nano-SiC was obtained on AZ91D magnesium alloy during MAO by adding nano-SiC into the silicate-aluminate-based composite electrolyte. The microstructure, thickness, phase analysis, element composition and hardness of the coatings were respectively investigated by scanning electron microscopy（SEM）, film thickness meter, X-ray diffraction （XRD）, energy disperse spectroscopy（EDS） and Vickers hardness tester. The wear resistance of Mg alloy and coatings were evaluated by friction and wear apparatus, while the corrosion resistance of Mg alloy and coatings were evaluated by potentiodynamic polarization test and electrochemical impedance spectroscopy （EIS）. The results show that after adding nano-SiC into the electrolyte, both the striking voltage and final voltage decrease, the size and number of the micropore on the surface of the coating decrease, the thickness and hardness of the coating increase, both the wear resistance and corrosion resistance of the coating raise.

Welding of Ti-6Al-4V alloy using dynamically controlled plasma arc welding process

A novel dynamically controlled plasma arc welding process was introduced,which is able tominimize heat input into the workpiece materials while maintaining desired full penetration,and it was used to weld Ti-6Al-4V alloy sheets.The microstructures,facture surfaces and microhardness of the welded joints were characterized by using optical microscope,scanning electron microscope （SEM） and Vickers microhardness tester.Comparing with welds such as gas tungsten arc and conventional plasma arc processes,the experimental results revealed the improvements when using the present process including：1） reducing prior-beta （β） grain size and prohibiting formation of hard martensite phases in the fusion zone due to the decreased heat input;and 2） better toughness and higher hardness.

Morphology and chemical composition of γ/γ' phases in Re-containing Ni-based single crystal superalloy during two-step aging

The γ/γ＇ microstructure of a Re-containing Ni-based single crystal super alloy after a two-step aging was studied using scanning electron microscopy （SEM）,transmission electron microscopy （TEM） and scanning transmission electron microscopy （STEM）.The crystals were grown by the floating zone （FZ） method.Both cuboidal and spherical γ＇ precipitates were formed after a two-step aging.The size of the cuboidal γ＇ phases first increased and then decreased with the extension of the second-step aging time.Re,Co and Cr strongly concentrated in the γ phase whereas Ni and Al enriched in the γ＇ phase.Thermodynamic calculation by JMatPro was performed to explain the experimental observations.

Microstructure of 18R-type long period ordered structure phase in Mg_(97)Y_2Zn_1 alloy

The microstructure of the 18R-type long period stacking ordered （LPSO） phase in Mg 97 Y 2 Zn 1 alloy was investigated by the first principles calculation. The arrangement rule of Zn and Y atoms in the LPSO structure is determined theoretically. The calculation results reveal that the additive atoms are firstly located in the fault layers at the two ends of the 18R-type LPSO structure, and then extend to fault layers in the interior, which is in good agreement with the experimental observations. This feature also implies the microstructural relationship between 18R and other LPSO structures. The cohesive energy and the formation heat indicate the dependence of the stability of 18R LPSO structure on contents of Y and Zn atoms. The calculated electronic structures reveal the underlying mechanism of microstructure and the stability of 18R LPSO structure.

Mechanical alloying and subsequent annealing effects on evolution of microstructure and morphology of TiH_2-Ni powders

Mechanical alloying and subsequent annealing treatment were carried out to investigate the evolution of the microstructure and morphology of the TiH2-Ni system. The Ni（Ti） solid solution was formed in the initial milling process. When the milling time was 60 h, the alloy with uniform elemental distribution showed an amorphous structure containing a small amount of TiH2 nanocrystalline phase. The annealing treatment at 693 K contributed to a completion of amorphization for the alloy milled for 60 h. For the treatment at 1 073 K, a crystallization reaction for the amorphous phase occurred, leading to the formation of Ti2Ni, TiNi, and TiNi3 compounds by a short time treatment. Moreover, a separation of Ni-rich phases from the matrix and a phase transition among these three compounds occur by a long time treatment.