Effect of phosphorus segregation on as-cast microstructure and homogenization treatment of IN706 alloy

The distribution of phosphorus in IN706 alloy was studied,with particular emphasis on the as-cast microstructure and homogenization treatment.It is found that phosphorus is segregated in Laves phase and markedly influences the as-cast microstructure of IN706 alloy.Phosphorus retards the formation of Laves phase with the eutectic form,but promotes the Laves formation with the blocky form.Phosphorus refines the dendritic structure and noticeably enlarges the interdendritic area.The reason for phosphorus influencing the as-cast microstructure is attributed to its extremely low solubility in γ matrix and great retarding effect on γ matrix solidification.In addition,phosphorus slightly decreases the melting temperature of Laves phase,and retards the dissolution of Laves phase and the element diffusion between dendrite core and interdendritic area during the homogenization treatment.And it is thought that phosphorus delays the homogenization process by inhibiting the element diffusion.

Recent advances in hydrothermal modification of calcium phosphorus coating on magnesium alloy

Magnesium(Mg) and its alloys have emerged as a favored candidate for bio-regenerative medical implants due to their superior biocompatibility, biodegradability and the elastic modulus close to that of human bone. Unfortunately, the rapid and uncontrollable degradation rate of Mg alloys in chloride-rich body microenvironments limits their clinical orthopedic applications. Recently, Calcium Phosphate(Ca-P)biomaterials, especially Hydroxyapatite(HA), have been broadly applied in the surface functional modification of metal-based biomaterials attributed to their excellent bioactivity and biocompatibility. Hydrothermal modification of Ca-P coatings on Mg alloys has been extensively exploited by researchers for its significant superiorities in controlling coating structure and improving interfacial bonding strength for better osseointegration and corrosion resistance. This work focuses on the up-to-the-minute advances in Ca-P coatings on the surface of Mg and its alloys via hydrothermal methods, including the strategies and mechanisms of hydrothermal modification. Herein, we are inclined to share some feasible and attractive hydrothermal surface modification strategies. From the perspectives of hydrothermal manufacturing technique innovation and coating structure optimization, we evaluate how to foster the corrosion resistance, coating bonding strength, osseointegration and antibacterial properties of Mg alloys with Ca-P coatings synthesized by hydrothermal method. The challenges and future perspectives on the follow-up exploration of Mg alloys for orthopedic applications are also elaborately proposed.

Effect of Phosphorus on Stress Rupture Properties of GH4133 Ni-Base Superalloy

The effect of phosphorus on the stress rupture property of GH4133 alloy has been investigated and is compared with that of IN718 alloy. The GH4133 alloy is crept by dislocation movement. Phosphorus has a tendency to prolong the rupture life of some wrought superalloys by inhibiting the dislocation movement. If the phosphorus addition is too high, its effect on impairing the grain boundary cohesion overwhelms that on inhibiting the dislocation movement, and the life of the GH4133 alloy can be shortened. The two functions of inhibiting the dislocation movement and impairing the grain boundary cohesion determine that the optimum phosphorus content in the GH4133 alloy is around 0.011 wt pet. Phosphorus exhibits a greater effect on prolonging the rupture life of IN718 alloy than that of GH4133 alloy. The two alloys are crept by different mechanisms. The intergranular phosphorus-bearing phase is precipitated in the IN718 alloy, while not in the GH4133 alloy. The precipitation of the phosphorus bearing phase can balance the phosphorus segregation at the grain boundaries and allows a more remarkable effect of phosphorus on extending the rupture life of IN718 alloy.

Hydrogen Content and Porosity Behavior of Hypereutectic Aluminum-silicon Alloy with Phosphorus

By making castings that pick up gas from moisture in red sand molds,the porosity generated at different cooling rates was discussed during solidification of hypereutectic Al-25%Si alloy without and with phosphorus additions. The effect of phosphorus addition on hydrogen content in the melt was also studied. It was observed that the phosphorus addition made hydrogen content in alloy melts present a “see-saw' tendency.In addition to primary silicon refinement,the phosphorus promoted gas porosity formed not only in slowly cooled sections, but also in rapidly cooled sections. There was a small difference in density of full dense sample between P-refined and unrefined castings, with a larger density associated with phosphorous addition. The change of the surface tension seemed more reasonable to explain the mechanism of porosity behavior.

EFFECT OF HIGH TEMPERATURE REPRESSING ON PHOSPHORUS SEGREGATION IN 93W-4.5Ni-2.5Fe ALLOY

The influence of high temperature repressing treatment on the segregation of phosphorus in the 93W alloy was carefully investigated by means of Auger electron spectroscope,EPMA, TEM and SEM.The segregation of phosphorus has been observed at the tungsten-tungsten grain boundaries,particularly at the tungsten-matrix interphases when the specimens were kept at the temperature in the range of 1200—1500℃ ,followed by furnace cooling.However, no segregation of phosphorus was observed at the interfaces after the specimens were re- pressed at the range of temperature,followed by furnace cooling.After investigation,the dis- locations in the matrix phase of as-repressed specimens directly influenced the phosphorus segregation to the interfaces.After annealing,the mechanical properties were reduced because of the phosphorus segregation at the interface boundaries.

Effect of additives on iron recovery and dephosphorization by reduction roasting-magnetic separation of refractory high-phosphorus iron ore

The effect of CaCO_(3),Na_(2)CO_(3),and CaF_(2) on the reduction roasting and magnetic separation of high-phosphorus iron ore containing phosphorus in the form of Fe_(3)PO_(7) and apatite was investigated.The results revealed that Na_(2)CO_(3) had the most significant effect on iron recovery and dephosphorization,followed by CaCO_(3),the effect of CaF_(2) was negligible.The mechanisms of CaCO_(3),Na_(2)CO_(3),and CaF_(2) were investigated using X-ray diffraction(XRD),scanning electron microscopy and energy dispersive spectrometry(SEM-EDS).Without additives,Fe_(3)PO_(7) was reduced to elemental phosphorus and formed an iron-phosphorus alloy with metallic iron.The addition of CaCO_(3) reacted with Fe_(3)PO_(7) to generate an enormous amount of Ca_(3)(PO_(4))_(2) and promoted the reduction of iron oxides.However,the growth of iron particles was inhibited.With the addition of Na_(2)CO_(3),the phosphorus in Fe_(3)PO_(7) migrated to nepheline and Na_(2)CO_(3) improved the reduction of iron oxides and growth of iron particles.Therefore,the recovery of iron and the separation of iron and phosphorus were the best.In contrast,CaF_(2) reacted with Fe_(3)PO_(7) to form fine Ca_(3)(PO_(4))2 particles scattered around the iron particles,making the separation of iron and phosphorus difficult.

Effects of P addition on the microstructure and mechanical properties of Mg–5%Sn–1.25%Si alloy

The effects of Al-P addition on the microstructure and mechanical properties of as-cast Mg–5%Sn–1.25%Si magnesium alloy were investigated. The results show that the phases of the as-cast alloy are composed of α-Mg, Mg2 Sn, Mg2 Si, little P, and AlP. The Chinese character shape Mg2 Si phase changes into a granular morphology by P addition because AlP can act as a heterogeneous nucleation core for the Mg2 Si phase. When 0.225wt% of Al–3.5%P alloy is added, the mechanical properties of the Mg–5%Sn–1.25%Si alloy are greatly improved, and the tensile strength increases from 156 to 191 MPa, an increase of 22.4% compared to the alloy without P addition. When the amount of Al–3.5%P reaches 0.300wt%, a segregation phenomenon occurs in the granular Mg2 Si phase, and the tensile strength and hardness decrease though the elongation increases.

ELECTRODEPOSITION OF AMORPHOUS Ni-P ALLOY COATINGS

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Effect of Carbon on DA718 Alloy with P Addition

Lower content of carbon can further improve the stress rupture life of p-modified DA 718 alloy up to more than 270%. Meanwhile, the ductility of the alloy decreased a little. More boron atoms dissociate due to decreasing carbon content and interact with phosphorus which brings the longer stress rupture life of the alloy. Less carbon may induce more phosphorus segregating in the grain boundary and result in brittleness.

Application of CX-type modifiers in Al-Si alloys

The modification effect of CX-type (CX means the modifiers that have longeffective term) modifiers applied in ZL108 and ZL104 Al-Si alloys has been studied in detail. Theresults show that the morphologies of the eutectic silicon and the primary silicon can be modifiedand refined simultaneously. The modification effect acts quickly and can maintain a period of 8 h bythe CX-type modifiers. The CX-type modifiers increase the mechanical properties of Al-Si alloys andimprove the service properties of machine parts made of Al-Si alloys (such as piston and cylinderetc.). In modifying processes, the amount of the addition of CX-type modifiers is smaller than thatof any other modifiers, and the modifying procedures are simple. There are no smoke, no dust, and noirritant smell in modifying processes using CX-type modifiers. Therefore, the CX-type modifiershave advantages in economy and environment protection.

Seamlessly Merging the Capacity of P into Sb at Same Voltage with Maintained Superior Cycle Stability and Low-temperature Performance for Li-ion Batteries

Among the alloying-type anodes,elemental Sb possesses the suitable yet safe plateau,simple lithiation pathway,small voltage polarization,high conductivity,and superior cycle stability.However,challenge is that its intrinsic capacity is rather low(660 mAh g^(-1)),<1/6 of silicon.Herein,we propose a seamless integration strategy by merging the voltage and capacity of phosphorus and antimony into a solid solution alloy.Interestingly,the enlistment of P is found greatly enlarge the capacity from 660 to 993 mAh g^(-1) for such Sb_(30)P_(30) solid solution,while maintaining a single and stable discharge plateau(~0.79 V)similar to elemental Sb.Various experimental characterizations including XPS,PDF,Raman,and EDS mapping reveal that in such a material the P and Sb atoms have interacted with each other to form a homogenous solid solution alloy,rather than a simple mixing of the two substances.Thus,the Sb_(30)P_(30) exhibits superior rate performances(807 mAh g^(-1) at 5000 mA g^(-1))and cyclability(821 mAh g^(-1) remained after 300 cycles).Furthermore,such Sb_(60-x)P_(x) alloys can even deliver 621 mAh g^(-1) at
30℃,which can be served as the alternative anode materials for high-energy and low-temperature batteries.This unique seamless integration strategy based on solid solution chemistry can be easily leveraged to manipulate the capacity of other electrode materials at similar voltage.

Segregation of Phosphorus and Precipitation of MNP-Type Phosphide at the Grain Boundary of IN706 Superalloy

The effect of phosphorus content and heat treatment on the segregation of phosphorus and precipita- tion of phosphide at the grain boundary of IN706 alloy has been investigated, The phosphide had a stoichiometry of MNP （M = Nb, Ti and N = Ni, Fe, Cr） and an orthorhombic crystal structure. The solubil- ity of phosphorus in the grain matrix of IN706 alloy was determined to be between 0.008% and 0.013%. When soaked at 980 ℃ for 5 min, the phosphide was noticeably precipitated at grain boundaries with the grain size unchanged. When soaked at 980 ℃ for 3 h, the grains grew significantly, but the phos- phide stayed at original grain boundaries which outlined the grain shape before soaking. Soaking at 1060 ℃ for 2 h fully dissolved the pre-existing phosphide but phosphorus atoms were not distributed uni- formly in the grain matrix. When the holding time at 1060 ℃ was extended to 10 h, the phosphorus atoms were distributed uniformly in the grain matrix by sufficient diffusion, and the phosphide could only be formed at grain boundaries during the 980 ℃ soaking. The precipitation of phosphide mainly relied on the phosphorus segregation which was built up by diffusion.

Effect of cooling rate on phosphorus segregation behavior and the corresponding precipitation of γ’’ and γ’ phases in IN718 alloy

Effect of segregation behaviors of P at different cooling rates on the precipitation of γ" and γ' phases and the corresponding strength are investigated. The precipitation of γ" and γ' phases during cooling is sensi-tive to P concentration. With increasing the concentration of Pf the amount of γ" and γ' particles increases after air cooling. With decreasing the cooling rate, the accelerating effect of P on the precipitation of γ" and γ' phases decreased first and then increased, which demonstrates the concentration of P dissolved in the grain interior decreases first and then increases. The different effects of P on γ"and γ' phases with different cooling rates were analyzed by the kinetic characteristic of nonequilibrium grain-boundary seg-regation. The characteristic of nonequilibrium grain-boundary segregation of P in superalloy is further confirmed, and the phenomenon caused by critical cooling rate is captured.

LPE Growth of InAsPSb on InAs:Melt Composition,Lattice Mismatch and Surface Morphology

The LPE growth of quaternary InAs11-x-yPxSby with x = 0.2 and y = 0.09 on InAs substrate has been studied. This composition is very suitable for the laser and detector applications at about 2.5 μm. We show that in InAsPSb/InAs system there is a determinate relation between the surface morphology and the lattice mismatch of the epi-wafers, by which we can easily control the melt composition to grow high quality hetero-structures. The reason has been discussed. The p-n junctions with fairly good carrier profile have been prepared in this system.

Distribution of Phosphorus and Its Effects on Precipitation Behaviors and Tensile Properties of IN718C Cast Superalloy

The effect of phosphorus on the precipitations of γ",γ’ and δ phases and associated tensile properties in IN718C alloy are investigated in this study.It is revealed that P atoms are dissolved in the grain interior to a relatively high degree and hence influence the precipitation behaviors in the grain interior and improve the tensile strength of IN718C alloy.γ" and γ’ phases did not precipitate in the alloy without P addition during air cooling,while γ" and γ’ phases precipitated in the grain interior during air cooling in the alloys with P addition,and the amounts of γ" and γ’ phases increased with increasing P content.Therefore,the Vickers micro-hardness in the as-cast state increased gradually with increasing P content.In double-aging state,the sizes of γ" and γ’ phases in the alloys with P addition were larger than that in the alloy without P addition,while the sizes were invariable when the P content(wt%)was higher than 0.015.Therefore,the micro-hardness and tensile strength of IN718C alloy treated by double aging increased first and then kept invariable with increasing P content.The precipitations of δ phases both in the grain interior and on grain boundaries were inhibited by P markedly.The inhibitory effect of P on δ phase enhanced gradually with increasing content of P,but the plasticity increased first and then decreased.What is more,the crack tended to propagate into the matrix around the particles(Laves phases and NbC carbides)in the alloys without P addition at the beginning of the tensile fracture,while it tended to propagate along the interfaces between the matrix and those particles in the alloys with P addition,which resulted from the synthetical effect of P on γ" γ’ and δ phases.

Effects of Phosphorus and Iron on Microstructures and Mechanical Properties in NiCrFe-Based Alloys

The microstructures and mechanical properties, especially creep properties, of the NiCrFe-based alloys with various contents of phosphorus and iron were investigated. The results showed that the tensile yield strength decreased with increasing iron contents while had no obvious change with the addition of phosphorus. For creep properties, the alloy with15.8 wt% iron and 0.09 wt% phosphorus possessed the longest creep life(679 h) among all alloys. Only M_(23)C_6 was formed in the alloys with low phosphorus contents, while both intergranular M_3P and M_(23)C_6 precipitated with the increment of phosphorus, which enhanced the strength of grain boundary by hindering the movements of dislocations during creep tests. The reasons for the enhancement of creep life were mainly related to the solid solution strengthening effect of phosphorus and optimization of grain boundary precipitations by phosphorus.

Tribological behavior of black phosphorus nanosheets as water-based lubrication additives

Black phosphorus(BP)with a layered structure has been used gradually as a lubrication additive in the tribological area.In this study,BP powders are produced via an easy method of high-energy ball milling using red phosphorus as a raw material.Subsequently,BP nanosheets are prepared via liquid exfoliation in N-methyl pyrolidone solvent.The tribological behavior of BP nanosheets as water-based lubrication additives(BP-WL)is evaluated under Ti6Al4V(TC4)/GCr15 contact.The results suggest that the 70 mg/L BP-WL sample exhibits excellent lubrication performance,whose coefficient of friction(COF)and ball wear rate reduced by 32.4%and 61.1%,respectively,compared with those of pure water.However,as the load increased,the tribological properties of BP-WL reduced gradually because of the agglomeration of BP nanosheets.Based on tribological experiments and worn surface analysis,boundary lubrication mechanisms are proposed.The friction reduced,which is primarily attributed to the low interlaminar shear and adsorption of BP nanosheets.In addition,a tribochemical reaction film comprising TiO_(2),Al_(2)O_(3),and Fe_(2)O_(3)effectively protects the surface of titanium alloy/steel from wear.This new water-based lubrication additive can be used to process titanium alloys.

Influence of phosphorous on nucleation and growth of grains during solidification in a NiCrFe alloy

The influence of phosphorus on the solidification of a NiCrFe model alloy has been investigated through a series of analytical techniques. It was found that increasing phosphorous additions greatly influenced the as-cast microstructure, changing from equiaxed grains to columnar grains in the center of ingots. It is indicated that the increase of phosphorous reduced the nucleation of grains and promoted dendrite growth during solidification. Furthermore, the addition of phosphorus in alloys also caused the segregation and phase transformation at grain boundaries and in interdendritic regions. The mechanism by which phosphorus influence the solidification of alloys was discussed based on experimental results as well.

Investigation of GaN-based dual-wavelength light-emitting diodes with p-type barriers and vertically stacked quantum wells

Designs of p-doped in quantum well （QW） barriers and specific number of vertically stacked QWs are proposed to improve the optical performance of GaN-based dual-wavelength light-emitting diodes （LEDs）. Emission spectra, carrier concentration, electron current density, and internal quantum efficiency （IQE） are studied numerically. Simulation results show that the efficiency droop and the spectrum intensity at the large current injection are improved markedly by using the proposed design. Compared with the conventional LEDs, the uniform spectrum intensity of dual-wavelength luminescence is realized when a specific number of vertically stacked QWs is adopted. Suppression of electron leakage current and the promotion of hole injection efficiency could be one of the main reasons for these improvements.