In-situ Micro-CT analysis of deformation behavior in sandwich-structured meta-stable beta Ti−35Nb alloy

Beta Ti−35Nb sandwich-structured composites with various reinforcing layers were designed and produced using additive manufacturing(AM)to achieve a balance between light weight and high strength.The impact of reinforcing layers on the compressive deformation behavior of porous composites was investigated through micro-computed tomography(Micro-CT)and finite element method(FEM)analyses.The results indicate that the addition of reinforcement layers to sandwich structures can significantly enhance the compressive yield strength and energy absorption capacity of porous metal structures;Micro-CT in-situ observation shows that the strain of the porous structure without the reinforcing layer is concentrated in the middle region,while the strain of the porous structure with the reinforcing layer is uniformly distributed;FEM analysis reveals that the reinforcing layers can alter stress distribution and reduce stress concentration,thereby promoting uniform deformation of the porous structure.The addition of reinforcing layer increases the compressive yield strength of sandwich-structured composite materials by 124%under the condition of limited reduction of porosity,and the yield strength increases from 4.6 to 10.3 MPa.

Microstructural evolution during aging of Ti-10V-2Fe-3Al titanium alloy

The development of microstructure during the aging of Ti-10V-2Fe-3A1 alloy in the 13 and （α＋β） solution-treated and quenched conditions was investigated. The results showed that the isothermal holding below 400℃ yielded homogeneously distributed, spherical ω-phase particles. Fine α aggregates are formed uniformly within 13 grains by nucleating at at particles or β/ω interfaces. At higher temperatures, thin martensite plates decomposed in water-quenched condition. The formation of ω phase was avoided and coarse coarse α-phase plates directly precipitated from the 13 matrix. The highest hardness values were found when the alloys were aged at 400℃ for 8 h. The significance of the observations was discussed in terms of the effect of aging on the precipitations and property.

Biomedical titanium alloys and their additive manufacturing

Titanium and its alloys have been widely used for biomedical applications due to their better biomechanical and biochemical compatibility than other metallic materials such as stainless steels and Co-based alloys.A brief review on the development of the b-type titanium alloys with high strength and low elastic modulus is given and the use of additive manufacturing technologies to produce porous titanium alloy parts,using Ti-6Al-4V as a reference,and its potential in fabricating biomedica replacements are discussed in this paper.

Microstructure and mechanical properties of a new high-strength and high-toughness titanium alloy

In order to develop a new titanium alloy with a good combination of strength-ductility-toughness,a nearbeta titanium alloy was designed based on the already widely used Ti-1023 alloy.To avoid beta fleck occurring in the microstructure,the new Ti-Al-Fe-V(Cr,Zr) alloy has been made through decreasing the content of Fe,based on molybdenum equivalency and Bo-Md molecular orbital method(a method for new alloy designing based on the molecular orbital calculating).After primary design computation,Ti-Al-Fe-V(Cr,Zr) alloy was optimized as Ti-3Al-4.5Cr-1Fe-4V-1Zr finally.The microstructure and tensile properties of this alloy subjected to several commonly used heat treatments were investigated.The results show that the tensile strength of the alloy after solution treated below the β-transus temperature comes between 850 and 1100 MPa,with elongation in the range of 12.5 %-17.0 %.In solution-treated and solution-aged samples,a low-temperature aging at 500 ℃ results in the precipitation of finer α phase.With the increase in aging temperature,the secondary α phase becomes coarser and decreases in amount.Thus,it will lead to the increase in tensile ductility,but reduction in strength.Eventually,after modulated aging treatment,the alloy can obtain highstrength level with acceptable ductility.The tensile strength of the alloy can achieve 1273 MPa,with an elongation of 11.0 %.At the same time,the fracture toughness(K_(IC)) of the alloy achieves 83.8 MPa·m^(1/2).It is obvious that the newly designed alloy has achieved a good blend of strength-ductility-toughness.