Improvement of microstructure and mechanical properties of TiAl-Nb alloy by adding Fe element

In order to improve mechanical properties and optimize composition of TiAl-Nb alloys, Ti46 Al5 Nb0.1 B alloys with different contents of Fe(0, 0.3, 0.5, 0.7, 0.9, and 1.1 at.%) were prepared by melting. Macro/microstructure and compression properties of the alloys were systematically investigated. Results show that Fe element can decrease the grain size, aggravate the Al-segregation and also form the Fe-rich B2 phase in the interdendritic area. Compressive testing results indicate that the Ti46 Al5 Nb0.1 B0.3 Fe alloy shows the highest ultimate compressive strength and fracture strain, which are 1869.5 MPa and 33.53%, respectively. The improved ultimate compression strength is ascribed to the grain refinement and solid solution strengthening of Fe, and the improved fracture strain is due to the reduced lattice tetragonality of γ phase and grain refinement of the alloys. However, excessive Fe addition decreases compressive strength and fracture strain, which is caused by the severe Al-segregation.

A high-Nb TiAl alloy with highly refined microstructure and excellent mechanical properties fabricated by electromagnetic continuous casting

In the present research, microstructure refinement of a high-Nb TiAl alloy （Ti-48Al-8Nb-0.15B） was realized by means of the electromagnetic continuous casting （EMCC） technique. The microstructure of an ingot obtained by EMCC was analyzed using scanning electron microscopy （SEM）. As compared with the raw as-cast alloy, the obtained EMCC alloy presented a much finer microstructure with lamellar colonies with a mean size of about 50-70 μm because the electromagnetic stirring broke initial dendrites and enhanced the heterogeneous nucleation. As the grains were refined, the properties of the TiAl alloy were improved significantly. This implies that the EMCC technique could offer the possibility of application for high-Nb TiAl alloys with a refined microstructure and excellent properties to be used as a structural material.

Effect of Zr on microstructure and mechanical properties of binary TiAl alloys

Ti43Al and Ti47Al alloys with different contents of zirconium were prepared by non-consumable vacuum arc melting furnace.The microstructure and mechanical properties were investigated.The results showed that Zr had no obvious effect on microstructure morphology of Ti43Al,while that of Ti47Al was modified from dendrites into equiaxed grains.The addition of Zr could refine the grains.Zr promoted the formation ofγphase significantly and the solubility values of Zr inγphase were 12.0%and 5.0%(molar fraction)in Ti43Al and Ti47Al,respectively.Zr-richγphase mainly formed throughβ→γin Ti43Al-xZr(molar fraction,%)andβ→α→γin Ti47Al-xZr(molar fraction,%).Fine-grain strengthening and solution strengthening were beneficial to improving the compressive strength while severe micro-segregation was detrimental to compressive properties.Large solubility of Zr was bad for ductility of alloys as well.The maximum compressive strengths of Ti43Al-xZr and Ti47Al-xZr were 1684.82 MPa(x=5.0%)and 2158.03 MPa(x=0.5%),respectively.The compressive strain fluctuated slightly in Ti43Al-xZr and reached the maximum value of 35.24%(x=0.5%)in Ti47Al-xZr.Both alloys showed brittle fracture.

Dependency of microstructure and microhardness on withdrawal rate of Ti-43Al-2Cr-2Nb alloy prepared by electromagnetic cold crucible directional solidification

The intermetallic Ti-43Al-2Cr-2Nb(at.%)alloy was directionally solidified in an electromagnetic cold crucible with different withdrawal rates(V)ranging from 0.2 to 1.0 mm·min^(-1),at a constant temperature gradients(G=18 K·mm^(-1)).Macrostructures of the alloy were observed by optical microscopy.Microstructures of the alloy were characterized by scanning electron microscopy(SEM)in back-scattered electron mode and transmission electron microscopy.Results showed that morphologies of macrostructure depend greatly on the applied withdrawal rate.Continuous columnar grains can be obtained under slow withdrawal rates ranging from 0.2 to 0.6 mm·min^(-1).The microstructure of the alloy was composed ofα_(2)/γlamellar structures and a small number of mixtures of B2 phases and blockyγphases.The columnar grain size(d)and interlamellar spacing(λ)decrease with an increasing withdrawal rate.The effect of withdrawal rate on microhardness was also investigated.The microhardness of the directional y solidified Ti-43Al-2Cr-2Nb alloy increases with an increase in withdrawal rate.This is mainly attributed to the increase of B2 andα_(2) phases as well as the refinement of lamellae.

Effect of boron on microstructure and mechanical properties of cast Ti-44Al6-Nb ingots

In order to improve the mechanical properties of Ti Al alloys, especially the ductility at room temperature, and to study the effect of boron(B) on Ti Al alloys, different contents(0, 0.1, 0.3, 0.6, 0.9, 1.2, at.%) of B were added into Ti-44Al-6Nb alloys to prepare ingots. The surface quality, macrostructure, microstructure, compressive properties and fracture surface of the ingots were studied. The results show that B has little influence on the surface quality except that there are some dark spots on the surface when the content of B is 0.9%. B can refine the grains. The average grain size decrease from about 0.8 mm to 0.088 mm with increasing B content. Meanwhile, the grain morphology of these ingots changes from big equiaxed grains with lamellars to fine equiaxed grains. When the content of B is 1.2%, the primary Ti B2 phase forms in the liquid phase and increases the nucleation rate, leading to further refinement of the grains. The compressive testing results show that B can increase the strength and the ductility, the compressive strength and compressibility can reach 2,037.8 MPa and 26.7% from 1,156.2 MPa and 10.2% when the boron content is 0.6%, which is resulted from grain refining and grain boundary strengthening. It is found that the compressive strength and the compressibility are relatively stable when the B content is more than 0.3%.

Microstructure and mechanical properties of Ni3Al intermetallics prepared by directional solidification electromagnetic cold crucible technique

The present work focused on the Ni_3Al-based alloy with a high melting point. The aim of the research is to study the effect of withdrawal rate on the microstructures and mechanical properties of directionally solidified Ni-25 Al alloy. Ni_3 Al intermetallics were prepared at different withdrawal rates by directional solidification(DS) in an electromagnetic cold crucible directional solidification furnace. The DS samples contain Ni_3 Al and Ni Al phases. The primary dendritic spacing(λ) decreases with the increasing of withdrawal rate(V), and the volume fraction of Ni Al phase increases as the withdrawal rate increases. Results of tensile tests show that ductility of DS samples is enhanced with a decrease in the withdrawal rate.

Cluster analysis of Qian Jing-hua’s experience in treatment of lung cancer

Objective to analyze the rule of drug use in treating lung cancer disease by using the theory of fuzheng and dispelling evil in traditional Chinese medicine by data mining.Methods:By following Dr.Qianjinghua's outpatient department,we collected the prescription for the treatment of lung cancer by using frequency analysis,association rule analysis and cluster analysis.Results:746 prescriptions were included in this study,commonly used drugs 170 flavors.Traditional Chinese medicine with a high frequency of use were Baihuasheshecao(Hedyotis diffusa),Maorenshen(Actinidia valvata Dunn),Shishangbai(Selaginella doederleinii Hieron),Shijianchuan(Salvia chinensis Benth),Huangqi(Astragali Radix),Sanyeqing(Tetrastlgma hemsleyanum),Baimaoteng(HerbaSolani),Zhuling(Polyporus),Nvzhenzi(Ligustrum lucidum Ait)etc.Through the analysis of association rule,we find out the core prescription according to the support degree(10%,20%,30%)and the confidence degree,and set the correlation degree to 8 and punishment degree to 2.Finally:The core prescription efficacy of the drug group was analyzed and the theoretical connotation of preventive treatment of disease was obtained.Conclusion:The core prescription of preventive treatment of disease is to clear up heat and detoxification on the basis of strengthening the spleen,replenishing qi and tonifying kidney.The use of blood supplements and yin tonics throughout the course is reduced during treatments.The treatments also pay attention to the function of spleen and stomach of lung cancer patients,and adjust heat and detoxification force according to different conditions of patients and pay attention to the relief of patients’emotions.

Microstructure and mechanical properties of Ti44Al6Nb1Cr2V alloy after gaseous hydrogen charging at 1373-1693 K

The hydrogenation behavior of Ti44A16Nb1Cr2V(at%)alloy at temperature range of 1373-1693 K and its effect on microstructure and room-temperature mechanical properties were studied systematically in this study.The results show that hydrogen content increases with the increase in temperature,and the maximum hydrogen content is 0.126 wt%at 1693 K.The heat of solution of hydrogen is calculated as 82.9 kJ·mol^(-1)by curve fitting,indicating that hydrogen absorptionin TiAl alloys is endothermic.Hydrogen promotes the lamellar colony size because hydrogen promotes the diffusion of elements.Hydrogen stabilizes B2phase during hydrogenation resulting in more residual B2phase in the hydrogenated alloy.The nanohardness and elastic modulus decrease after hydrogenation due to that hydrogen weakens the bonds.The Ti44A16Nb1Cr2V alloy exhibits higher plasticity and lower flow stress hydrogenation with 0.039 wt%H,and the ultimate compressive strength decreases from 1220 to 1130 MPa,while the fracture strain is enhanced by 26%.

Microstructure and mechanical properties of Ti43Al6Nb alloys with different zirconium contents

Ti43Al6Nb-xZr alloys with different additions of zirconium were prepared by vacuum arc melting furnace.The microstructure and compressive properties at room temperature(RT) were investigated.The microstructure shows dendrites with addition of 0 at%-2.5at% Zr,and the dendrites are refined with the primary dendrite arms spacing decreasing from 222.64 μm(0 at%Zr) to 92.57 μm(2.0 at% Zr).With Zr addition more than2.5 at%,the microstructure shows equiaxed grains surrounded by y phase.Zr is a y stabilizer and promotes the β/y transition,resulting in the change of microstructure morphology.Zr reaches the maximum solid solubility(about 6.5 at%) in y phase with addition of 2.5 at% Zr;moreover,γ phase increases in quantity,bringing about severe micro-segregation.With addition of Zr,the remained β phase turns into ω phase with B82 structure.Ti43Al6Nb-xZr alloys show brittle fracture.The maximum compressive strength is 2161.69 MPa with addition of 2.5at% Zr and the maximum compressive strain is 30.62%with addition of 0.5 at% Zr,improving by 9.24% and7.33%,respectively.The improvement of compressive strength results from fine-grain strengthening and solution strengthening.Severe micro-segregation is bad for compressive strength,and large solubility of Zr is detrimental to ductility.

Magnetic field annealing of FeCo-based amorphous alloys to enhance thermal stability and Curie temperature

Annealing temperatures and applied magnetic fields are two important parameters for the performance modification of magnetic alloys.This article investigated the effect of different annealing temperatures on crystallization condition,magnetic properties and thermal stability of the amorphous magnetic alloy Co_(36)Fe_(36)Si_(4.8)B1_(9.2)Nb_(4)(at%).Results indicate that the annealing temperature can significantly affect the size and content of precipitated nanocrystals in the amorphous alloy,and the precipitation of nanocrystalline phases can result in the distinct change of magnetic properties and Curie temperature.When the annealing was performed at 595 ℃ for 30 min under an applied transverse external magnetic field of 9550.0A·m^(-1),the amorphous alloy shows excellent soft magnetic properties with the saturation magnetization of alloy reaching 110.00 mA·m^(2)·g^(-1),the residual magnetic induction intensity of 4 × 10^(-6) T and the coercivity as low as57.3 A·m^(-1).Furthermore,the Curie temperature of the field-annealed samples can reach up to 440 0C,approximately 58℃ higher than that of the as-quenched species.

Improving microstructure and mechanical properties of Ti43Al5Nb0.1B alloy by addition of Fe

Alloying additions of 0 at%-1.1 at% Fe were added into Ti43A1Nb0.1B alloys for increasing the roomtemperature strength and ductility,and the microstructure and mechanical properties were systematically studied.The results show that the lattice tetragonality(c/a) of γ phase and the average width of columnar grains of alloys decrease with Fe content increasing.Fe addition brings about the formation of Fe-rich B2 phase both in the dendrites and in interdendritic regions,and its content increases with Fe contents increasing.Furthermore,Fe addition aggravates the Al segregations in the interdendritic regions.The alloy with 0.7 at% Fe exhibits higher combined mechanical properties with the ultimate compression strength and fracture strain of 1958.4 MPa and 29.8%,respectively.The grain refinement strengthening and solid-solution strengthening of Fe are responsible for the improvement in the strength and the strain.However,excessive Fe addition results in the decrease in the strength and strain,which is attributed to the severe A1 segregations in the interdendritic regions that cause the premature fracture during compression.

Microstructure and mechanical properties of Ti44Al6Nb alloys with different cerium contents

Ti44A16 Nb-based alloy ingots with different cerium(Ce)contents(0,0.05,0.10,0.15,0.20;at%)were prepared by non-consumable vacuum arc smelting furnace(WK-Ⅱ).The surface quality,macrostructure,microstructure,compressive properties and fracture morphology of these ingots were studied.The results show that Ce has few influences on the surface quality.Ce can refine grain size and the average grain size decreases from 0.50 to 0.19 mm with the increase of Ce content.Meanwhile,the microstructure morphology of these ingots changes from large lamellar microstructure to dual-phase microstructure.With addition of Ce,CeO and AlCe3 are formed during melting and solidifying,which act as the core of heterogeneous nucleation and refine the grain.The compressive testing results show that Ce can improve strength and ductility.The ultimate compressive strength increases from 1156.2 to 1472.2 MPa with Ce content increasing from 0 at%to 0.20 at%.The compression ratio is improved from 10.2%to 15.3%with Ce content increasing from 0 at%to 0.10 at%.The refined crystalline strengthening and grain boundary strengthening are the main reasons for the improvement of compressive property.