Effect of Ti Additions on Mechanical and Thermodynamic Properties of W-Ti Alloys: A First-principles Study

The mechanical and thermodynamic properties of W-Ti alloys(including W_(15)Ti_(1),W_(14)Ti_(2),W_(12)Ti_(4) and W_(8)Ti_(8) alloys)were investigated by the first-principles approach based on density functional theory.The results indicate that W-Ti alloys except W_(8)Ti_(8) are thermodynamically stable.The modulus and hardness of W-Ti alloys are smaller than those of pure tungsten and gradually decrease with increasing Ti concentration.However,their B/G ratios and Poisson's ratios exceed those of pure tungsten,suggesting that the introduction of Ti decreases the mechanical strength while enhancing the ductility of W-Ti alloys.The thermal expansion coefficients for W-Ti alloys all surpass those of pure tungsten,indicating that the introduction of titanium exacerbates the thermal expansion behavior of W-Ti alloys.Nevertheless,elevated pressure has the capacity to suppress the thermal expansion tendencies in titanium-doped tungsten alloys.This study offers theoretical insights for the design of nuclear materials by exploring the mechanical and thermodynamic properties of W-Ti alloys.

Understanding the local structure and thermophysical behavior of Mg-La liquid alloys via machine learning potential

The local structure and thermophysical behavior of Mg-La liquid alloys were in-depth understood using deep potential molecular dynamic(DPMD) simulation driven via machine learning to promote the development of Mg-La alloys. The robustness of the trained deep potential(DP) model was thoroughly evaluated through several aspects, including root-mean-square errors(RMSEs), energy and force data, and structural information comparison results;the results indicate the carefully trained DP model is reliable. The component and temperature dependence of the local structure in the Mg-La liquid alloy was analyzed. The effect of Mg content in the system on the first coordination shell of the atomic pairs is the same as that of temperature. The pre-peak demonstrated in the structure factor indicates the presence of a medium-range ordered structure in the Mg-La liquid alloy, which is particularly pronounced in the 80at% Mg system and disappears at elevated temperatures. The density, self-diffusion coefficient, and shear viscosity for the Mg-La liquid alloy were predicted via DPMD simulation, the evolution patterns with Mg content and temperature were subsequently discussed, and a database was established accordingly. Finally, the mixing enthalpy and elemental activity of the Mg-La liquid alloy at 1200 K were reliably evaluated,which provides new guidance for related studies.

Numerical simulation of microstructure and microporosity morphology in directional solidification of aluminum-copper alloys:Effect of copper content and withdrawal rate

Microporosity formed in the solidification process of Al alloys is detrimental to the alloy properties.A two-dimensional cellular automaton(CA)model was developed to simulate the microstructure and microporosity formation in Al-Cu alloys,considering variations in Cu content and solidification rate.The results indicate that the Cu content primarily influences the growth of microporosity.To validate the model,directional solidification experiments were conducted on Al-Cu alloys with varing Cu contents and withdrawal rates.The experimental results of dendrites and microporosity characteristics agree well with the predictions from the developed model,thus confirming the validity of the model.The alloy’s liquidus temperature,dendrite morphology,and hydrogen saturation solubility arising from different Cu contents have significant effects on microporosity morphology.The withdrawal rate primarily affects the nucleation of hydrogen microporosity by altering cooling rates and dendritic growth rates,resulting in different microporosity characteristics.

轧制方向对Zr-Sn-Nb合金耐腐蚀性能的影响

利用电子背散射衍射、电化学工作站、扫描电镜等方法,对不同轧制方向的Zr-Sn-Nb合金板材进行微观结构分析和电化学腐蚀性能分析。结果表明,交叉轧制有利于晶粒细化。热轧板材的织构取向主要以<1120>//RD和<1010>//RD为主。交叉轧制弱化锆合金板材的择优取向。交叉轧制通过控制微观组织结构调控了锆合金的耐腐蚀性能,有效地提高锆合金板材的耐腐蚀性能,使得腐蚀速率为沿RD轧制的9.27%。

接头性能差异对Zr-Sn-Nb合金电子束焊接头残余应力的影响

为了提升Zr-Sn-Nb合金电子束焊残余应力计算精度,对Zr-Sn-Nb合金及焊接接头热物性参数与力学性能进行测量,研究接头性能差异对电子束焊接头残余应力影响规律,建立了电子束焊复合热源模型,采用热弹塑性有限元方法对4.45mm厚Zr-Sn-Nb合金电子束焊应力进行数值模拟,并进行焊缝形貌验证.结果表明,考虑焊缝与母材属性差异时,试板上表面焊缝及热影响区区域的横向残余应力峰值高于二者属性相同时的模拟结果,峰值分别为319 MPa和296 MPa,进一步考虑热影响区属性与母材及焊缝差异对接头残余应力影响不大,峰值纵向应力为318 MPa.

Microstructure and mechanical properties stability of pre-hardening treatment in Al-Cu alloys for pre-hardening forming process

The stability of the microstructure and mechanical properties of the pre-hardened sheets during the pre-hardening forming(PHF)process directly determines the quality of the formed components.The microstructure stability of the pre-hardened sheets was in-vestigated by differential scanning calorimetry(DSC),transmission electron microscopy(TEM),and small angle X-ray scattering(SAXS),while the mechanical properties and formability were analyzed through uniaxial tensile tests and formability tests.The results in-dicate that the mechanical properties of the pre-hardened alloys exhibited negligible changes after experiencing 1-month natural aging(NA).The deviations of ultimate tensile strength(UTS),yield strength(YS),and sheet formability(Erichsen value)are all less than 2%.Also,after different NA time(from 48 h to 1 month)is applied to alloys before pre-hardening treatment,the pre-hardened alloys possess stable microstructure and mechanical properties as well.Interestingly,with the extension of NA time before pre-hardening treatment from 48 h to 1 month,the contribution of NA to the pre-hardening treatment is limited.Only a yield strength increment of 20 MPa is achieved,with no loss in elongation.The limited enhancement is mainly attributed to the fact that only a limited number of clusters are transformed into Guinier-Preston(GP)zones at the early stage of pre-hardening treatment,and the formation ofθ''phase inhibits the nucleation and growth of GP zones as the precipitated phase evolves.

Accelerated design of high-performance Mg-Mn-based magnesium alloys based on novel bayesian optimization

Magnesium(Mg),being the lightest structural metal,holds immense potential for widespread applications in various fields.The development of high-performance and cost-effective Mg alloys is crucial to further advancing their commercial utilization.With the rapid advancement of machine learning(ML)technology in recent years,the“data-driven''approach for alloy design has provided new perspectives and opportunities for enhancing the performance of Mg alloys.This paper introduces a novel regression-based Bayesian optimization active learning model(RBOALM)for the development of high-performance Mg-Mn-based wrought alloys.RBOALM employs active learning to automatically explore optimal alloy compositions and process parameters within predefined ranges,facilitating the discovery of superior alloy combinations.This model further integrates pre-established regression models as surrogate functions in Bayesian optimization,significantly enhancing the precision of the design process.Leveraging RBOALM,several new high-performance alloys have been successfully designed and prepared.Notably,after mechanical property testing of the designed alloys,the Mg-2.1Zn-2.0Mn-0.5Sn-0.1Ca alloy demonstrates exceptional mechanical properties,including an ultimate tensile strength of 406 MPa,a yield strength of 287 MPa,and a 23%fracture elongation.Furthermore,the Mg-2.7Mn-0.5Al-0.1Ca alloy exhibits an ultimate tensile strength of 211 MPa,coupled with a remarkable 41%fracture elongation.

Relationship between the unique microstructures and behaviors of high-entropy alloys

High-entropy alloys(HEAs),which were introduced as a pioneering concept in 2004,have captured the keen interest of nu-merous researchers.Entropy,in this context,can be perceived as representing disorder and randomness.By contrast,elemental composi-tions within alloy systems occupy specific structural sites in space,a concept referred to as structure.In accordance with Shannon entropy,structure is analogous to information.Generally,the arrangement of atoms within a material,termed its structure,plays a pivotal role in dictating its properties.In addition to expanding the array of options for alloy composites,HEAs afford ample opportunities for diverse structural designs.The profound influence of distinct structural features on the exceptional behaviors of alloys is underscored by numer-ous examples.These features include remarkably high fracture strength with excellent ductility,antiballistic capability,exceptional radi-ation resistance,and corrosion resistance.In this paper,we delve into various unique material structures and properties while elucidating the intricate relationship between structure and performance.

Research advances of magnesium and magnesium alloys globally in 2023

Magnesium materials have attracted the attention of many researchers,and the related research is expanding.This article summarizes the advance in the research and development of magnesium materials globally in 2023 from bibliometric and scientific perspectives.More than 4680 articles on Mg and its alloys were published and indexed in the Web of Science(WoS)Core Collection database last year.The bibliometric analyses show that the traditional structural Mg alloys,functional Mg materials,and corrosion and protection of Mg alloys are still the main research focus.Therefore,this review paper mainly focuses on the research progress of Mg cast alloys,Mg wrought alloys,bio-magnesium alloys,Mg-based energy storage materials,corrosion and protection of Mg alloys in 2023.In addition,future research directions are proposed based on the challenges and obstacles identified throughout this review.

Influence of Metalloid Elements on the Magnetic Properties and Anisotropy of FeNi-based Amorphous Alloys

The magnetic properties and anisotropy of amor- phous(Fe_(80)Ni_(20))_(78)Si_xB_(22-x).alloys have been investigated systematically.The maximum permeability,coercive force and remanence have been determined for as-prepared and annealed samples,The results on the technical magnetic properties of this alloy system have been discussed and compared with Masumoto's.

Microstructure and damping properties of LPSO phase dominant Mg-Ni-Y and Mg-Zn-Ni-Y alloys

This work studied the microstructure,mechanical properties and damping properties of Mg_(95.34)Ni_(2)Y_(2.66) and Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloys systematically.The difference in the evolution of the long-period stacked ordered(LPSO)phase in the two alloys during heat treatment was the focus.The morphology of the as-cast Mg_(95.34)Ni_(2)Y_(2.66)presented a disordered network.After heat treatment at 773 K for 2 hours,the eutectic phase was integrated into the matrix,and the LPSO phase maintained the 18R structure.As Zn partially replaced Ni,the crystal grains became rounded in the cast alloy,and lamellar LPSO phases and more solid solution atoms were contained in the matrix after heat treatment of the Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloy.Both Zn and the heat treatment had a significant effect on damping.Obvious dislocation internal friction peaks and grain boundary internal friction peaks were found after temperature-dependent damping of the Mg_(95.34)Ni_(2)Y_(2.66)and Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloys.After heat treatment,the dislocation peak was significantly increased,especially in the alloy Mg_(95.34)Ni_(2)Y_(2).66.The annealed Mg_(95.34)Ni_(2)Y_(2.66)alloy with a rod-shaped LPSO phase exhibited a good damping performance of 0.14 atε=10^(−3),which was due to the difference between the second phase and solid solution atom content.These factors also affected the dynamic modulus of the alloy.The results of this study will help in further development of high-damping magnesium alloys.

Recent innovations in laser additive manufacturing of titanium alloys

Titanium(Ti)alloys are widely used in high-tech fields like aerospace and biomedical engineering.Laser additive manufacturing(LAM),as an innovative technology,is the key driver for the development of Ti alloys.Despite the significant advancements in LAM of Ti alloys,there remain challenges that need further research and development efforts.To recap the potential of LAM high-performance Ti alloy,this article systematically reviews LAM Ti alloys with up-to-date information on process,materials,and properties.Several feasible solutions to advance LAM Ti alloys are reviewed,including intelligent process parameters optimization,LAM process innovation with auxiliary fields and novel Ti alloys customization for LAM.The auxiliary energy fields(e.g.thermal,acoustic,mechanical deformation and magnetic fields)can affect the melt pool dynamics and solidification behaviour during LAM of Ti alloys,altering microstructures and mechanical performances.Different kinds of novel Ti alloys customized for LAM,like peritecticα-Ti,eutectoid(α+β)-Ti,hybrid(α+β)-Ti,isomorphousβ-Ti and eutecticβ-Ti alloys are reviewed in detail.Furthermore,machine learning in accelerating the LAM process optimization and new materials development is also outlooked.This review summarizes the material properties and performance envelops and benchmarks the research achievements in LAM of Ti alloys.In addition,the perspectives and further trends in LAM of Ti alloys are also highlighted.

Effect of icosahedral phase formation on the stress corrosion cracking(SCC)behaviors of the as-cast Mg-8%Li(in wt.%)based alloys

Through exploring the stress corrosion cracking(SCC)behaviors of the as-cast Mg-8%Li and Mg-8%Li-6%Zn-1.2%Y alloys in a 0.1 M NaCl solution,it revealed that the SCC susceptibility index(I_(SCC))of the Mg-8%Li alloy was 47%,whilst the I_(SCC)of the Mg-8%Li-6%Zn-1.2%Y alloy was 68%.Surface,cross-sectional and fractography observations indicated that for the Mg-8%Li alloy,theα-Mg/β-Li interfaces acted as the preferential crack initiation sites and propagation paths during the SCC process.With regard to the Mg-8%Li-6%Zn-1.2%Y alloy,the crack initiation sites included the I-phase and the interfaces of I-phase/β-Li andα-Mg/β-Li,and the preferential propagation paths were the I-phase/β-Li andα-Mg/β-Li interfaces.Moreover,the SCC of the two alloys was concerned with hydrogen embrittlement(HE)mechanism.

Prediction of the thermal conductivity of Mg–Al–La alloys by CALPHAD method

Mg-Al alloys have excellent strength and ductility but relatively low thermal conductivity due to Al addition.The accurate prediction of thermal conductivity is a prerequisite for designing Mg-Al alloys with high thermal conductivity.Thus,databases for predicting temperature-and composition-dependent thermal conductivities must be established.In this study,Mg-Al-La alloys with different contents of Al2La,Al3La,and Al11La3phases and solid solubility of Al in the α-Mg phase were designed.The influence of the second phase(s) and Al solid solubility on thermal conductivity was investigated.Experimental results revealed a second phase transformation from Al_(2)La to Al_(3)La and further to Al_(11)La_(3)with the increasing Al content at a constant La amount.The degree of the negative effect of the second phase(s) on thermal diffusivity followed the sequence of Al2La>Al3La>Al_(11)La_(3).Compared with the second phase,an increase in the solid solubility of Al in α-Mg remarkably reduced the thermal conductivity.On the basis of the experimental data,a database of the reciprocal thermal diffusivity of the Mg-Al-La system was established by calculation of the phase diagram (CALPHAD)method.With a standard error of±1.2 W/(m·K),the predicted results were in good agreement with the experimental data.The established database can be used to design Mg-Al alloys with high thermal conductivity and provide valuable guidance for expanding their application prospects.

Review on synergistic damage effect of irradiation and corrosion on reactor structural alloys

The synergistic damage effect of irradiation and corrosion of reactor structural materials has been a prominent research focus.This paper provides a comprehensive review of the synergistic effects on the third-and fourth-generation fission nuclear energy structural materials used in pressurized water reactors and molten salt reactors.The competitive mechanisms of multiple influencing factors,such as the irradiation dose,corrosion type,and environmental temperature,are summarized in this paper.Conceptual approaches are proposed to alleviate the synergistic damage caused by irradiation and corrosion,thereby promoting in-depth research in the future and solving this key challenge for the structural materials used in reactors.

Microstructures,corrosion behavior and mechanical properties of as-cast Mg-6Zn-2X(Fe/Cu/Ni)alloys for plugging tool applications

Mg-6Zn-2X(Fe/Cu/Ni)alloys were prepared through semi-continuous casting,with the aim of identifying a degradable magnesium(Mg)alloy suitable for use in fracturing balls.A comparative analysis was conducted to assess the impacts of adding Cu and Ni,which result in finer grains and the formation of galvanic corrosion sites.Scanner electronic microscopy examination revealed that precipitated phases concentrated at grain boundaries,forming a semi-continuous network structure that facilitated corrosion penetration in Mg-6Zn-2Cu and Mg-6Zn-2Ni alloys.Pitting corrosion was observed in Mg-6Zn-2Fe,while galvanic corrosion was identified as the primary mechanism in Mg-6Zn-2Cu and Mg-6Zn-2Ni alloys.Among the tests,the Mg-6Zn-2Ni alloy exhibited the highest corrosion rate(approximately 932.9 mm/a)due to its significant potential difference.Mechanical testing showed that Mg-6Zn-2Ni alloy possessed suitable ultimate compressive strength,making it a potential candidate material for degradable fracturing balls,effectively addressing the challenges of balancing strength and degradation rate in fracturing applications.

Effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on tensile and bending properties of high-Al-containing Mg alloys

This study investigates the effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on the uniaxial tensile and three-point bending properties of extruded Mg alloys containing high Al contents.The extruded Mg–9Al–1Zn–0.3Mn(AZ91)alloy contains lamellar-structured Mg_(17)Al_(12)discontinuous precipitates along the grain boundaries,which are formed via static precipitation during natural air cooling.The extruded Mg–11Al–1Zn–0.3Mn(AZ111)alloy contains spherical Mg_(17)Al_(12)precipitates at the grain boundaries and inside the grains,which are formed via dynamic precipitation during extrusion.Due to inhomogeneous distribution of precipitates,the AZ111 alloy consists of two different precipitate regions:precipitate-rich region with numerous precipitates and finer grains and precipitate-scarce region with a few precipitates and coarser grains.The AZ111 alloy exhibits a higher tensile strength than the AZ91 alloy because its smaller grain size and more abundant precipitates result in stronger grain-boundary hardening and precipitation hardening effects,respectively.However,the tensile elongation of the AZ111 alloy is lower than that of the AZ91 alloy because the weak cohesion between the dynamic precipitates and the matrix facilitates the crack initiation and propagation.During bending,a macrocrack initiates on the outer surface of bending specimen in both alloys.The AZ111 alloy exhibits higher bending yield strength and lower failure bending strain than the AZ91 alloy.The bending specimens of the AZ91 alloy have similar bending formability,whereas those of the AZ111 alloy exhibit considerable differences in bending formability and crack propagation behavior,depending on the distribution and number density of precipitates in the specimen.In bending specimens of the AZ111 alloy,it is found that the failure bending strain(ε_(f,bending))is inversely proportional to the area fraction of precipitates in the outer zone of bending specimen(A_(ppt)),with a relationship ofε_(f,bending)=–0.1A_(ppt)+5.86.

Phase transformation in titanium alloys:A review

Due to a series of exceptional properties,titanium and titanium alloys have received extensive attention in recent years.Different from other alloy systems,there are two allotropes and a sequence of metastable phases in titanium alloys.By summarizing the recent investigations,the phase transformation processes corresponding to the common phases and also some less reported phases are reviewed.For the phase transformation only involvingαandβphases,it can be divided intoβ→αtransformation and a reverse transformation.The former one has been demonstrated from the orientation relationship betweenαandβphases and the regulation ofαmorphology.For the latter transformation,the role of the stress has been discussed.In terms of the metastable phases,the mechanisms of phase formation and their effects on microstructure and mechanical properties have been discussed.Finally,some suggestions about the development of titanium alloys have been proposed.

Structural,mechanical and electronic properties of precipitates in Mg−Zn alloys

To accelerate the development and design of magnesium(Mg)alloys,the structural and mechanical properties of important precipitates in Mg−Zn alloys were studied by experiments and density functional theory.The nano-indentation tests revealed that the hardness of the precipitates initially increased and then decreased with increasing Zn content,and was significantly higher than that of pure Mg and Zn.The calculation results revealed that the precipitates stability initially increased and then decreased with increasing Zn concentration.The bulk moduli of the precipitates increased,whereas their shear and Young’s moduli initially increased and then decreased with increasing Zn content.The decreasing order of ductility for these compounds is MgZn_(2)>Mg_(21)Zn_(25)>Mg_(2)Zn_(11)>Mg_(4)Zn_(7).The surface profiles of the compounds revealed that they are obvious anisotropy.Both the degree of covalency and bond length of covalent bonds initially increased and then decreased with increasing Zn content.

The influence of yttrium and manganese additions on the degradation and biocompatibility of magnesium-zinc-based alloys:In vitro and in vivo studies

The repair and regeneration of bone defects are highly challenging orthopedic problems.Recently,Mg-based implants have gained popularity due to their unique biodegradation and elastic modulus similar to that of human bone.The aim of our study is to develop a magnesium alloy with a controllable degradation that can closely match bone tissue to help injuries heal in vivo and avoid cytotoxicity caused by a sudden increase in ion concentration.In this study,we prepared and modified Mg-3Zn,Mg-3Zn-1Y,and Mg-2Zn-1Mn by hot extrusion,and used Mg-2.5Y-2.5Nd was as a control.We then investigated the effect of additions of Y and Mn on alloys'properties.Our results show that Mn and Y can improve not only compression strength but also corrosion resistance.The alloy Mg-2Zn-1Mn demonstrated good cytocompatibility in vitro,and for this reason we selected it for implantation in vivo.The degraded Mg-2Zn-1Mn implanted a bone defect area did not cause obvious rejection and inflammatory reaction,and the degradation products left no signs of damage to the heart,liver,kidney,or brain.Furthermore,we find that Mg-2Zn-1Mn can promote an osteoinductive response in vivo and the formation of bone regeneration.