A novel Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy designed using cluster-plus-glue-atom model for laser additive manufacturing

A novel Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy was designed using the cluster formula approach(cluster-plus-glue-atom model)and prepared by laser melting deposition(LMD).Its composition formula 12[Al-Ti_(12)](AlTi_(2))+5[Al_(0.8)Si_(0.2)-Ti_(12)Zr_(2)](V_(0.8)Mo_(0.2)Nb_(1)Ti)features an enhancedβ-Ti via co-alloying of Zr,V,Mo,Nb and Si.The experimental results show that the cluster formula ofαandβphases in the novel alloy are respectivelyα-[Al-Ti_(11.5)Zr_(0.5)](Al_(1)Ti_(2))andβ-[Al_(0.8)Si_(0.2)-Ti_(13.2)Zr_(0.8)](V_(1)Mo_(0.4)Nb_(1.6)),both containing Zr elements.The fitted composition via the α andβphase cluster formulas has little difference with the actual alloy composition,suggesting that the validity of cluster-plus-glue-atom model in the alloy composition design.After hot isostatic pressing(HIP),both the Ti-6Al-4V and the novel alloy by LMD are characterized by prior-βcolumnar grains,while the typical<100>texture disappears.Compared with Ti-6Al-4V,Ti-5.55Al-6.70Zr-1.50V-0.70Mo-3.41Nb-0.21Si alloy exhibits a combination of higher strength(1,056 MPa)and higher ductility(14%)at room temperature and higher strength(580 MPa)at 550℃ after HIP,and can potentially serves as LMD materials.

Microstructures and mechanical properties of Ti−Al−V−Nb alloys with cluster formula manufactured by laser additive manufacturing

Ti−Al−V−Nb alloys with the cluster formula,12[Al−Ti_(12)](AlTi_(2))+5[Al−Ti1_(4)](V,Nb)2Ti,were designed by replacing V with Nb based on the Ti−6Al−4V alloy.Single-track cladding layers and bulk samples of the alloys with Nb contents ranging from 0 to 6.96 wt.%were prepared by laser additive manufacturing to examine their formability,microstructure,and mechanical properties.For single-track cladding layers,the addition of Nb increased the surface roughness slightly and decreased the molten pool height to improve its spreadability.The alloy,Ti−5.96Al−1.94V−3.54Nb(wt.%),exhibited better geometrical accuracy than the other alloys because its molten pool height was consistent with the spread layer thickness of the powder.The microstructures of the bulk samples contained similar columnar β-phase grains,regardless of Nb content.These grains grew epitaxially from the Ti substrate along the deposition direction,with basket-weaveα-phase laths within the columnar grains.Theα-phase size increased with increasing Nb contents,but its uniformity decreased.Along the deposition direction,the Vickers hardness increased from the substrate to the surface.The Ti−5.96Al−1.94V−3.54Nb alloy exhibited the highest Vickers hardness regardless of deposition position because of the optimal matching relationship between theα-phase size and its content among the designed alloys.

Design for Ti-Al-V-Mo-Nb alloys for laser additive manufacturing based on a cluster model and on their microstructure and properties

In this study,α+βTi-Al-V-Mo-Nb alloys with the addition of multiple elements that are suitable for laser additive manufacturing(LAM)were designed according to a Ti-6Al-4V cluster formula.This formula can be expressed as 12[Al-Ti12](AlTi2)+5[Al-Ti14]((Mo,V,Nb)2Ti),in which Mo and Nb were added into the alloys partially instead of V to give alloys with nominal compositions of Ti-6.01Al-3.13V-1.43Nb,Ti-5.97Al-2.33V-2.93Mo,and Ti-5.97Al-2.33V-2.20Mo-0.71Nb(wt.%).The microstructures and mechanical properties of the as-deposited and heat-treated samples prepared via LAM were examined.The sizes of theβcolumnar grains andαlaths in the Nb-containing samples are found to be larger than those of the Ti-6Al-4V alloy,whereas Mo-or Mo/Nb-added alloys contain finer grains.It indicates that Nb gives rise to coarsenedβcolumnar grains andαlaths,while Mo significantly refines them.Furthermore,the single addition of Nb improves the elongation,whereas the single addition of Mo enhances the strength of the alloys.The simultaneous addition of Mo/Nb significantly improves the comprehensive mechanical properties of the alloys,leading to the best properties with an ultimate tensile strength of 1,070 MPa,a yield strength of 1,004 MPa,an elongation of 9%,and micro-hardness of 355 HV.The fracture modes of all the alloys are ductile-brittle mixed fracture.

Laser additive manufacturing of biodegradable Mg-based alloys for biomedical applications: A review

Metallic implants are widely used in internal fixation of bone fracture in surgical treatment.They are mainly used for providing mechanical support and stability during bone reunion,which usually takes a few months to complete.Conventional implants made of stainless steels,Ti-based alloys and CoCrMo alloys have been widely used for orthopedic reconstruction due to their high strength and high corrosion resistance.Such metallic implants will remain permanently inside the body after implantation,and a second surgery after bone healing is needed because the long-term presence of implant will lead to various problems.An implant removal surgery not only incurs expenditure,but also risk and psychological burden.As a consequence,studies on the development of biodegradable implants,which would degrade and disappear in vivo after bone reunion is completed,have drawn researchers’attention.In this connection,Mg-based alloys have shown great potentials as promising implant materials mainly due to their low density,inherent biocompatibility,biodegradability and mechanical properties close to those of bone.However,the high degradation rate of Mg-based implants in vivo is the biggest hurdle to overcome.Apart from materials selection,a fixation implant is ideally tailor-made in size and shape for an individual case,for best surgical outcomes.Therefore,laser additive manufacturing(LAM),with the advent of sophisticated laser systems and software,is an ideal process to solve these problems.In this paper,we reviewed the progress in LAM of biodegradable Mg-based alloys for biomedical applications.The effect of powder properties and laser processing parameter on the formability and quality was thoroughly discussed.The microstructure,phase constituents and metallurgical defects formed in the LAMed samples were delineated.The mechanical properties,corrosion resistance,biocompatibility and antibacterial properties of the LAMed samples were summarized and compared with samples fabricated by traditional processes.In addition,we have made some suggestions for advancing the knowledge in the LAM of Mg-based alloys for biomedical implants.

Influence of heat treatments on microstructure and mechanical properties of laser additive manufacturing Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy

The effect of heat treatments on laser additive manufacturing(LAM)Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy(TC17)was studied aiming to optimize its microstructure and mechanical properties.The as-deposited sample exhibits features of a mixed priorβgrain structure consisting of equiaxed and columnar grains,intragranular ultra-fineαlaths and numerous continuous grain boundaryα(αGB).After being pre-annealed inα+βregion(840°C)and standard solution and aging treated,the continuousαGB becomes coarser and the precipitate free zone(PFZ)nearby theαGB transforms into a zone filled with ultra-fine secondaryα(αS)but no primaryα(αP).When pre-annealed in singleβregion(910°C),allαphases transform intoβphase and the alloying elements distribute uniformly near the grain boundary.DiscontinuousαGB and uniform mixture ofαP andαS near grain boundary form after subsequent solution and aging treatment.The two heat treatments can improve the tensile mechanical properties of LAM TC17to satisfy the aviation standard for TC17.

Microstructure and properties of Ti64.51Fe26.40Zr5.86Sn2.93Y0.30 biomedical alloy fabricated by laser additive manufacturing

From the perspective of biomechanics and forming technology,Ti−Fe−Zr−Sn−Y eutectic alloy was designed using a“cluster-plus-glue-atom”model,and then the alloy was prepared by laser additive manufacturing(LAM)on pure titanium substrate.The mechanical properties of the alloy were evaluated using micro-hardness and compression tester,and the elastic modulus was measured by nanoindenter.The results show that the alloy exhibits a high hardness of HV(788±10),a high strength of 2229 MPa,a failure strain of 14%,and a low elastic modulus of 87.5 GPa.The alloy also has good tribological,chemical,forming,and biological properties.The comprehensive performances of the Ti64.51Fe26.40Zr5.86Sn2.93Y0.30 alloy are superior to those of the Ti70.5Fe29.5 eutectic alloy and commercial Ti−6Al−4V alloy.All the above-mentioned qualities make the alloy a promising candidate as LAM biomaterial.

Microstructure and mechanical property of additively manufactured NiTi alloys:A comparison between selective laser melting and directed energy deposition

NiTi shape memory alloy(SMA)with nominal composition of Ni 50.8 at%and Ti 49.2 at%was additively manufactured(AM)by selective laser melting(SLM)and laser directed energy deposition(DED)for a comparison study,with emphasis on its phase composition,microstructure,mechanical property and deformation mechanism.The results show that the yield strength and ductility obtained by SLM are 100 MPa and 8%,respectively,which are remarkably different from DED result with 700 MPa and 2%.The load path of SLM sample presents shape memory effect,corresponding to martensite phase detected by XRD;while the load path of DED presents pseudo-elasticity with austenite phase.In SLM sample,fine grain and hole provide a uniform deformation during tensile test,resulting in a better elongation.Furthermore,the nonequilibrium solidification was studied by a temperature field simulation to understand the difference of the two 3D printing methods.Both temperature gradient G and growth rate R determine the microstructure and phase in the SLM sample and DED sample,which leads to similar grain morphologies because of similar G/R.While higher G×R of SLM leads to a finer grain size in SLM sample,providing enough driving force for martensite transition and subsequently changing texture compared to DED sample.

Subsurface Defect Evaluation of Selective-Laser-Melted Inconel 738LC Alloy Using Eddy Current Testing for Additive/Subtractive Hybrid Manufacturing

New materials and manufacturing technologies require applicable non-destructive techniques for quality assurance so as to achieve better performance.This study comprehensively investigated the effect of influencing factors includ-ing excitation frequency,lift-off distance,defect depth and size,residual heat,and surface roughness on the defect EC signals of an Inconel 738LC alloy produced by selective laser melting(SLM).The experimental investigations recorded the impedance amplitude and phase angle of EC signals for each defect to explore the feasibility of detecting sub-surface defects by merely analyzing these two key indicators.Overall,this study revealed preliminary qualitative and roughly quantitative relationships between influencing factors and corresponding EC signals,which provided a prac-tical reference on how to quantitively inspect subsurface defects using eddy current testing(ECT)on SLMed parts,and also made solid progress toward on-line ECT in additive/subtractive hybrid manufacturing(ASHM)for fabricating SLMed parts with enhanced quality and better performance.

Review on laser directed energy deposited aluminum alloys

Lightweight aluminum(Al)alloys have been widely used in frontier fields like aerospace and automotive industries,which attracts great interest in additive manufacturing(AM)to process high-value Al parts.As a mainstream AM technique,laser-directed energy deposition(LDED)shows good scalability to meet the requirements for large-format component manufacturing and repair.However,LDED Al alloys are highly challenging due to their inherent poor printability(e.g.low laser absorption,high oxidation sensitivity and cracking tendency).To further promote the development of LDED high-performance Al alloys,this review offers a deep understanding of the challenges and strategies to improve printability in LDED Al alloys.The porosity,cracking,distortion,inclusions,element evaporation and resultant inferior mechanical properties(worse than laser powder bed fusion)are the key challenges in LDED Al alloys.Processing parameter optimizations,in-situ alloy design,reinforcing particle addition and field assistance are the efficient approaches to improving the printability and performance of LDED Al alloys.The underlying correlations between processes,alloy innovation,characteristic microstructures,and achievable performances in LDED Al alloys are discussed.The benchmark mechanical properties and primary strengthening mechanism of LDED Al alloys are summarized.This review aims to provide a critical and in-depth evaluation of current progress in LDED Al alloys.Future opportunities and perspectives in LDED high-performance Al alloys are also outlined.

Characteristics of Biometallic Alloy to Additive Manufacturing Using Selective Laser Melting Technology

Biomaterial powders are in high development due to expansion of additive manufacturing (AM) processes. Selective laser melting (SLM) is a particular AM technology, which completely melts a powder bed layer by laser beam. Investigations of appropriated physical properties of feedstock (powder alloy) were the aim of this study. Cobalt-chromium-molybdenum (Co-Cr-Mo) alloy was used to overview of gas-atomized powder properties in different granulometric ranges (D1 12 - 19 μm, D2 20 - 46 μm and D3 76 - 106 μm), as their: physical, chemical properties and thermal analysis. SLM manufactured standard tensile specimens of usually granulometric range powder size provided mechanical, chemical and thermal properties of biocompatible Co-Cr-Mo alloy. The physical properties showed that powders in the range of 20 to 50 μm provide a better flow ability and packed density, which are relevant characteristics to SLM processing. Manufacturing by SLM process provided suitable mechanical properties in the health area, as well as, maintained the biocompatible properties of the Co-Cr-Mo alloy.

Study of the intrinsic mechanisms of nickel additive for grain refinement and strength enhancement of laser aided additively manufactured Ti–6Al–4V

It is well-known that grain refiners can tailor the microstructure and enhance the mechanical properties of titanium alloys fabricated by additive manufacturing(AM). However, the intrinsic mechanisms of Ni addition on AM-built Ti–6Al–4V alloy is not well established. This limits its industrial applications. This work systematically investigated the influence of Ni additive on Ti–6Al–4V alloy fabricated by laser aided additive manufacturing(LAAM). The results showed that Ni addition yields three key effects on the microstructural evolution of LAAM-built Ti–6Al–4V alloy.(a) Ni additive remarkably refines the prior-β grains, which is due to the widened solidification range. As the Ni addition increased from 0 to 2.5 wt. %, the major-axis length and aspect ratio of the prior-β grains reduced from over 1500 μm and 7 to 97.7 μm and1.46, respectively.(b) Ni additive can discernibly induce the formation of globular α phase,which is attributed to the enhanced concentration gradient between the β and α phases. This is the driving force of globularization according to the termination mass transfer theory. The aspect ratio of the α laths decreased from 4.14 to 2.79 as the Ni addition increased from 0 to2.5 wt. %.(c) Ni as a well-known β-stabilizer and it can remarkably increase the volume fraction of β phase. Room-temperature tensile results demonstrated an increase in mechanical strength and an almost linearly decreasing elongation with increasing Ni addition. A modified mathematical model was used to quantitatively analyze the strengthening mechanism. It was evident from the results that the α lath phase and the solid solutes contribute the most to the overall yield strength of the LAAM-built Ti–6Al–4V–x Ni alloys in this work. Furthermore, the decrease in elongation with increasing Ni addition is due to the deterioration in deformability of the β phase caused by a large amount of solid-solution Ni atoms. These findings can accelerate the development of additively manufactured titanium alloys.

Challenges and Solutions for the Additive Manufacturing of H) Biodegradable Magnesium Implants

Due to their capability of fabricating geometrically complex structures,additive manufacturing(AM)techniques have provided unprecedented opportunities to produce biodegradable metallic implants—especially using Mg alloys,which exhibit appropriate mechanical properties and outstanding biocompatibility.However,many challenges hinder the fabrication of AM-processed biodegradable Mg-based implants,such as the difficulty of Mg powder preparation,powder splash,and crack formation during the AM process.In the present work,the challenges of AM-processed Mg components are analyzed and solutions to these challenges are proposed.A novel Mg-based alloy(Mg-Nd-Zn-Zr alloy,JDBM)powder with a smooth surface and good roundness was first synthesized successfully,and the AM parameters for Mg-based alloys were optimized.Based on the optimized parameters,porous JDBM scaffolds with three different architectures(biomimetic,diamond,and gyroid)were then fabricated by selective laser melting(SLM),and their mechanical properties and degradation behavior were evaluated.Finally,the gyroid scaffolds with the best performance were selected for dicalcium phosphate dihydrate(DCPD)coating treatment,which greatly suppressed the degradation rate and increased the cytocompatibility,indicating a promising prospect for clinical application as bone tissue engineering scaffolds.

Effect of Nd addition on microstructure and tensile properties of laser additive manufactured TC11 titanium alloy

Single-layer and multilayer laser additive manufacturing(LAM)for TC11 alloy with different Nd additions was conducted and the effect of Nd addition on microstructure and properties was studied.With the addition of Nd,the aspect ratio of melting pools of single-layer specimens increases and the columnar-to-equiaxed transition occurs.The originalβgrain size andαplate width of TC11−1.0Nd are significantly reduced compared with those of pure TC11 specimens.It is proposed that the evenly distributed fine Nd_(2)O_(3) precipitates of about 1.51μm are formed preferentially during rapid solidification of melting pool,and they serve as heterogeneous nucleation particles to refine the microstructure in the subsequent solidification and solid-state phase transformation.Due to the multiple effects of Nd on the microstructure,the ultimate tensile strength of TC11−1.0Nd increases,while the yield strength,ductility and microhardness decrease compared with those of pure TC11.

Microstructure evolution and mechanical properties of laser additive manufactured Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy

The microstructure, microhardness and tensile properties of laser additive manufactured (LAM) Ti?5Al?2Sn?2Zr?4Mo?4Cr alloy were investigated. The result shows that the microstructure evolution is strongly affected by the thermal history of LAM process. Primary α (αp) with different morphologies, secondary α (αs) and martensite α' can be observed at different positions of the LAMed specimen. Annealing treatment can promote the precipitation of rib-like α phase or acicular α phase. As a result, it can increase or decrease the microhardness. The as-deposited L-direction and T-direction specimens contain the same phase constituent with different morphologies. The tensile properties of the as-deposited LAMed specimens are characterized of anisotropy. The L-direction specimen shows the character of low strength but high ductility when compared with the T-direction specimen. After annealing treatment, the strength of L-direction specimen increases significantly while the ductility reduces. The strength of the annealed T-direction specimen changes little, however, the ductility reduces nearly by 50%.

Microstructure and mechanical properties of laser additive manufactured novel titanium alloy after heat treatment

A novel α+β titanium alloy with multi-alloying addition was designed based on the cluster formula 12[Al-Ti_(12)](AlTi_(2))+5[Al-Ti_(14)](AlV_(1.2)Mo_(0.6)Nb_(0.2))which was derived from Ti-6Al-4V.The nominal composition of this novel alloy was determined as Ti-6.83Al-2.28V-2.14Mo-0.69Nb-6.79Zr.In this study,the novel alloy and Ti-6Al-4V alloy samples were prepared by laser additive manufacturing.The microstructure,micro-hardness,room/high temperature tensile properties of the as-deposited samples were investigated.Compared to Ti-6Al-4V,the novel alloy has much higher room and high temperature(600℃)tensile strengths,which are 1,427.5 MPa and 642.2 MPa,respectively;however,it has a much lower elongation(3.2%)at room temperature because of the finer microstructure.To improve the elongation of the novel alloy,heat treatment was used.After solution at 960℃ or 970℃ for 1 h followed by air cooling and aging at 550℃ for 4 h followed by air cooling,a unique bi-modal microstructure which contains crab-like primaryαand residual β phase is obtained,improving the compression elongation by 80.9% compared to the as-deposited samples.The novel alloy can be used as a high-temperature and high-strength candidate for laser additive manufacturing.

Electrochemical dissolution and passivation of laser additive manufactured Ti6Al4V controlled by elements segregation and phases distribution

The electrochemical dissolution and passivation of laser additive manufactured Ti6Al4V were investigated through Tafel polarization,potentiostatic polarization and AC impedance measurements.The results show that the solution treatment−aging(STA)process aggravates the element micro-segregation compared to the annealing process,leading to varied Al and V contents of the phases from different samples.It is proven that either Al-rich or V-rich condition can highly affect the electrochemical dissolution behaviors due to thermodynamical instability caused by element segregation.The dissolution rate in the metastable passivation process is controlled by the stability of the produced film that is affected by phases distribution,especially the difficult-to-dissolve phase.And then,the dissolution rate of the phases in the transpassivation region is consistent with the rank in the activation process because the dense film is not capable of being produced.Compared to the annealed sample,the higher dissolution rate of the STA sample is beneficial to the electrochemical machining(ECM)of Ti6Al4V.

Additively Manufactured High-Entropy Alloys:Exceptional Mechanical Properties and Advanced Fabrication

High-entropy alloys(HEA)represent a novel material class,with significant potential for research on performance and preparation in additive manufacturing(AM).Currently,FCC HEA dominates the research on AM-fabricated HEA,with a shift in focus from preparation to microstructure design and mechanical properties enhancement.Research on BCC HEA is currently primarily focused on preparation and process optimization.However,it is important to note that the biomedical potential of AM-fabricated BCC HEA should not be overlooked.This review provides a concise summary of the properties and preparation techniques of exceptional HEAs in recent years.It specifically emphasizes the novel microstructure achieved through AM techniques,which significantly enhance the mechanical properties of HEAs.Additionally,the review outlines the various preparation methods employed to mitigate defect introduction during AM processes.Finally,it offers insights into the future research directions and potential applications of additively manufactured HEA.

Additive manufacturing of metallic glasses and high-entropy alloys:Significance,unsettled issues,and future directions

As two kinds of well-known prominent high-performance alloys,metallic glasses(MGs)and high-entropy alloys(HEAs)have attracted increasing attention.Most of them contain multiple alloying components,demonstrate intriguing microstructures,and exhibit excellent properties;however,their unique performances are closely dependent on the fabrication process,although they are limited due to the need for rapid solidification during fabrication.On the other hand,additive manufacturing(AM)can be used to fabricate complex parts via rapid solidification,thus saving materials.These advantages provide AM with a great possibility to produce MG and HEA materials with tunable microstructures therefore properties,and corresponding parts with complex geometries,large dimensions,and more functions.This paper provides a comprehensive and systematic overview of the manufacturing and properties of MGs and HEAs using AM techniques.The correlation between MGs and HEAs with conventional manufacturing meth-ods and the difficulties encountered are retrospectively discussed.Afterward,this review specifically focuses on the recent research advances in MGs and HEAs fabricated using AM technologies.Then,various properties of the AM-fabricated MGs and HEAs are discussed.Finally,the remaining issues and potential solutions,challenges,and future directions on the AM of MGs and HEAs are also presented.

Heat-treated Nickel Alloys Produced Using Laser Powder Bed Fusion-based Additive Manufacturing Methods:A Review

Laser powder bed fusion(LPBF)is the most widely used metal additive manufacturing process.It is a novel layer-by-layer manufacturing technique based on a geometrical model that provides a suitable alternative for material processing.This mode is widely used in laser and electron beam welding.Nickel(Ni)alloy prepa-ration using the LPBF method has attracted considerable attention in several areas,owing to the high corro-sion resistance and good mechanical properties of the prepared alloys.The specific conditions of solidification through the metal fused during the selective laser fusion process and its layer deposition induces microstruc-tural peculiarities,including the formation of a supersaturated solid solution,extreme microstructural refine-ment,and the generation of residual stress.Consequently,heat treatment and hot isostatic pressing,which are generally applied to conventionally manufactured Ni alloys,may need to be altered to adapt to the met-allurgical properties of Ni alloys manufactured using direct metal laser deposition and address particular is-sues resulting from the process itself.Several studies have been conducted on this topic over the past few years,suggesting different approaches for addressing different alloying systems.This review summarizes the latest scientific findings in the area of thermal treatment for selective laser sintering of additively manufactured Ni alloys.

Laser metal deposition of refractory high-entropy alloys for high-throughput synthesis and structure-property characterization

Progress in materials development is often paced by the time required to produce and evaluate a large number of alloys with different chemical compositions.This applies especially to refractory high-entropy alloys(RHEAs),which are difficult to synthesize and process by conventional methods.To evaluate a possible way to accelerate the process,high-throughput laser metal deposition was used in this work to prepare a quinary RHEA,TiZrNbHfTa,as well as its quaternary and ternary subsystems by in-situ alloying of elemental powders.Compositionally graded variants of the quinary RHEA were also analyzed.Our results show that the influence of various parameters such as powder shape and purity,alloy composition,and especially the solidification range,on the processability,microstructure,porosity,and mechanical properties can be investigated rapidly.The strength of these alloys was mainly affected by the oxygen and nitrogen contents of the starting powders,while substitutional solid solution strengthening played a minor role.