Microstructure and mechanical properties of TC21 titanium alloy after heat treatment

Microstructure evolutions during different heat treatments and influence of microstmcture on mechanical properties of TC21 titanium alloy were investigated. The results indicate that the excellent mechanical properties can be obtained by adopting air cooling after forging followed by heat treatment of （900℃, 1 h, AC）＋（590 ℃, 4 h, AC）. Deformation in single β field produces pan-like prior fl grains, while annealing in single fl field produces equiaxed prior fl grains. Cooling rate after forging or annealing in single fl field and the subsequent annealing on the top of α＋β field determine the content and morphology of coarse a plates. During aging or the third annealing, fine secondary a plates precipitate. Both ultimate strength and yield strength decrease with the content increase of coarse a plates. Decreasing effective slip length and high crack propagation resistance increase the plasticity. The crisscross coarse a plates with large thickness are helpful to enhance the fracture toughness.

Influence of Zr content on microstructure and mechanical properties of implant Ti-35Nb-4Sn-6Mo-xZr alloys

The influence of Zr content on the microstructure and mechanical properties of implant Ti-35Nb-4Sn-6Mo-xZr （x=0, 3, 6, 9, 12, 15; mass fraction） alloys was investigated. It is shown that Ti-35Nb-4Sn-6Mo-xZr alloys appear to have equiaxed single β microstructure after solution treatment at 1023 K. It is found that the grains are refined first and then coarsened with the increase of Zr content. It is also found that Zr element added to titanium alloys has both the solution strengthening and fine-grain strengthening effect, and affects the lattice parameters. With increasing the Zr content of the alloys, the strength increases, the elongation decreases, whereas the elastic modulus firstly increases and then decreases. The mechanical properties of Ti-35Nb-4Sn-6Mo-9Zr alloy are as follows： σb=785 MPa, δ=11%, E=68 GPa, which is more suitable for acting as human implant materials compared to the traditional implant Ti-6Al-4V alloy.

Effects of microstructures on mechanical properties of Ti-63 titanium alloy

The microstructure and mechanical properties of Ti-63 pancakes were investigated under different heat-treatment modes. Pancake No. 1, with an as-forged bimodal structure, was β annealed at 930℃ for l h. Its structure was changed to a Widmanstatten structure with continuous grain boundary α phase and long lamellar α phase. The pancake showed a good combination of strength, ductility and fracture toughness. Pancake No. 2, with an as-forged bimodal structure, was aged at 540℃for 8 h after annealing at 930℃ for 1 h. Other than the t＇me secondary α precipitates, it showed a similar microstructure to that of pancake No. 1. The fine precipitates can enhance the pancake＇s strength while reducing the ductility and fracture toughness. Pancake No. 3, with an as-forged basket-weave structure, was annealed at 750℃ for 1 h. Its structure was nearly unchanged and it achieved a better ductility but a slightly lower fracture toughness than pancake No. 1.

Microstructure and mechanical properties of spark plasma sintered Ti–Mo alloys for dental applications

Ti-Mo alloys with various Mo contents from 6wt% to 14wt% were processed by spark plasma sintering based on elemental pow- ders. The influence of sintering temperature and Mo content on the microstructure and mechanical properties of the resulting alloys were investigated. For each Mo concentration, the optimum sintering temperature was determined, resulting in a fully dense and uniform microstructure of the alloy. The optimized sintering temperature gradually increases in the range of 1100-1300℃ with the increase in Mo content. The microstructure of the Ti-（6-12）Mo ahoy consists of acicular α phase surrounded by equiaxed grains of 13 phase, while the Ti-14Mo al- loy only contains single 13 phase. A small amount of fine α lath precipitated from 13 phase contributes to the improvement in strength and hardness of the alloys. Under the sintering condition at 1250℃, the Ti-12Mo alloy is found to possess superior mechanical properties with the Vickers hardness of Hv 472, the compressive yield strength of 2182 MPa, the compression rate of 32.7%, and the elastic modulus of 72.1 GPa. These results demonstrate that Ti-Mo alloys fabricated via spark plasma sintering are indeed a perspective candidate alloy for dental applications.

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.

Relationship among microstructure,mechanical properties and texture of TA32 titanium alloy sheets during hot tensile deformation

The relationship among microstructure,mechanical properties and texture of TA32 titanium alloy sheets during hot tensile deformation at 800℃was investigated.In the test,the original sheet exhibited relatively low flow stress and sound plasticity,and increasing the heat treatment temperature resulted in an increased ultimate tensile strength(UTS)and a decreased elongation(EL).The deformation mechanism of TA32 alloy was dominated by high angle grain boundaries sliding and coordinated by dislocation motion.The coarsening of grains and the annihilation of dislocations in heat-treated specimens weakened the deformation ability of material,which led to the increase in flow stress.Based on the high-temperature creep equation,the quantitative relationship between microstructure and flow stress was established.The grain size exponent andαphase strength constant of TA32 alloy were calculated to be 1.57 and 549.58 MPa,respectively.The flow stress was accurately predicted by combining with the corresponding phase volume fraction and grain size.Besides,the deformation behavior of TA32 alloy was also dependent on the orientation of predominantαphase,and the main slip mode was the activation of prismaticslip system.The decrease of near prism-oriented texture in heat-treated specimens resulted in the enhancement of strength of the material.

Microstructure and mechanical properties of laser additive repaired Ti17 titanium alloy

Laser additive manufacturing technology with powder feeding was employed to repair wrought Ti17titanium alloy with small surface defects.The microstructure,micro-hardness and room temperature tensile properties of laser additive repaired(LARed)specimen were investigated.The results show that,cellular substructures are observed in the laser deposited zone(LDZ),rather than the typicalαlaths morphology due to lack of enough subsequent thermal cycles.The cellular substructures lead to lower micro-hardness in the LDZ compared with the wrought substrate zone which consists of duplex microstructure.The tensile test results indicate that the tensile deformation process of the LARed specimen exhibits a characteristic of dramatic plastic strain heterogeneity and fracture in the laser repaired zone with a mixed dimple and cleavage mode.The tensile strength of the LARed specimen is slightly higher than that of the wrought specimen and the elongation of11.7%is lower.

Influence of multi-stage heat treatment on the microstructure and mechanical properties of TC21 titanium alloy

Duplex-structured TC21 alloy samples were first solution-treated at a higher temperature in theα+βregion(940°C)with furnace cooling(FC),air cooling(AC),and water cooling(WC),followed by a second-stage solution treatment at a lower temperature in theα+βregion(900°C),and then finally aged at 590°C.The effects of the morphology and quantity ofαphases on the structure and properties of the TC21 alloy after the different heat treatments were analyzed.The in-situ tensile deformation process and crack propagation behavior were observed using scanning electron microscopy(SEM).The quantity of equiaxedαphases as well as the thickness of lamellarαphases reduced,the tensile strength increased firstly and then decreased,the elongation decreased with the increasing cooling rate after the first-stage solution treatment.The amount and size of lamellarαphases increased after the second-stage solution treatment because of sufficient diffusion of the alloying elements,thereby leading to increased tensile strength.The amount of dispersedαphases increased after the third-stage aging treatment owing to the increase in the nucleation rate,resulting in a noteworthy strengthening effect.After the third-stage aging treatment,the first-stage FC sample exhibited better mechanical properties because it contained more equiaxedαandβtrans phases than the first-stage AC and WC samples.

Effects of titanium on microstructure and mechanical properties of ZnAl4Y alloy

The effect of Ti on the microstructure and mechanical properties of zinc-aluminum ZnAl4Y alloy has been investigated in this work. Small amount of Ti was added into ZnAl4Y alloy in the form of Al-10wt.%Ti alloy. The results show that Ti addition into ZnAl4Y alloy refines the primary η-Zn phase and increases the amount of η-Zn + α-Al eutectic structure. There exists a ternary T phase in Zn-Al-Ti alloy. Fine TiAl3 particles and Ti-Zn compounds can serve as the nucleation sites of the α-Al and η-Zn phase, respectively, resulting in the refining of the microstructure of ZnAl4Y alloy. Ti addition changes the fracture characteristics of ZnAl4Y alloy. With 0.05wt%Ti, the fracture surface of the alloy shows a lot of dimples and tearing ridges connecting the microscopic dimples, which is mainly ductile fracture morphology. Ti addition into ZnAl4Y alloy also increases the mechanical properties of the alloy. When the content of Ti is 0.05wt.%, the ZnAl4Y alloy possesses the best comprehensive mechanical properties.

Effect of duplex aging on microstructure and mechanical properties of near-βtitanium alloy processed by isothermal multidirectional forging

The effects of sub-transus(α+β)annealing treatment(ST),followed by single aging(SA)or duplex aging(DA)on the microstructural evolution and mechanical properties of near-βTi-4Al-1Sn-2Zr-5Mo-8V-2.5Cr(mass fraction,%)alloy were investigated using optical microscopy,scanning electron microscopy,and transmission electron microscopy.The results show that the finer secondaryαphase precipitates in the alloy after DA than SA(e.g.,149 nm for SA and 69 nm for DA,both after ST at 720℃).The main reason is that the pre-aging step(300℃)in the DA process leads to the formation of intermediateωphase nanoparticles,which assist in the nucleation of the acicular secondaryαphase precipitates.In addition,the strength of the alloy after DA is higher than that of SA at the specific ST temperature.A good combination is achieved in the alloy subjected to ST at 750℃,followed by DA(UTS:1450 MPa,EL:3.87%),which is due to the precipitation of nanoscale secondaryαphase by DA.In conclusion,DA is a feasible process for this new near-βtitanium alloy.

Microstructures and mechanical properties of a new titanium alloy for surgical implant application

A new titanium alloy Ti12.5Zr2.5Nb2.5Ta（TZNT） for surgical implant application was synthesized and fully annealed at 700℃for 45 min.The microstructure and the mechanical properties such as tensile properties and fatigue properties were investigated.The results show that TZNT mainly consists of a lot of lamellaα-phase clusters with different orientations distributed in the originalβ-phase grain boundaries and a small amount ofβphases between the lamella a phases.The alloy exhibits better ductility,lower modulus of elasticity,and lower admission strain in comparison with Ti6A14V and Ti6A17Nb,indicating that it has better biomechanical compatibility with human bones.The fatigue limit of TZNT is 333 MPa,at which the specimen has not failed at 10^7 cycles.A large number of striations present in the stable fatigue crack propagation area,and many dimples in the fast fatigue crack propagation area are observed,indicating the ductile fracture of the new alloy.

Microstructure and mechanical properties of powder metallurgy Ti-Al-Mo-V-Ag alloy

The Ti-Al-Mo-V-Ag α＋β alloys were processed by powder metallurgy（PM） using the blended elemental（BE） technique.The effects of Ag addition and sintering temperature on microstructure and properties of the Ti-5Al-4Mo-4V alloys were investigated using X-ray diffraction,optical microscope,scanning electron microscope and mechanical properties tests.The results show that adding Ag element increases the relative density and improves the mechanical properties of PM Ti-5Al-4Mo-4V alloy.After sintering at 1 250 ℃ for 4 h,the relative density and compression strength of Ti-5Al-4Mo-4V-5Ag alloy are 96.3% and 1 656 MPa,respectively.

Microstructures and mechanical properties of extruded Mg-1Mn-3.5Y and Mg-1Mn-1Y-2.5Nd alloys

Both Mg-1Mn-3.5Y and Mg-1Mn-1Y-2.5Nd alloys（mass fraction,%）were extruded at 380？C.Most of the（10^-10） crystal planes in the Mg-1Mn-3.5Y alloy are parallel to the normal direction,while most of the（10^-11）crystal planes in the Mg-1Mn-1Y-2.5Nd alloy are parallel to the normal direction.The tensile tests at room temperature,100℃ and 200℃ show that the Mg-1Mn-3.5Y alloy exhibits higher yield strength,but lower elongation to failure as compared with the Mg-1Mn-1Y-2.5Nd alloy. These differences in the tensile mechanical properties between the two alloys are mainly attributed to their different texture types and amount and distribution of the Mg24Y5 precipitates.The serration flow behavior is observed in the Mg-1Mn-1Y-2.5Nd alloy at 200℃,but does not occur in the Mg-1Mn-3.5Y alloy.The Mg-1Mn-3.5Y alloy shows the cleavage fracture mode,while the Mg-1Mn-1Y-2.5Nd alloy exhibits the dimple fracture mode.

Effect of Initial Microstructure on Phase Precipitation and Mechanical Properties during Heat Treatment of TC21 Titanium Alloy

Phase precipitation and mechanical properties of TC21 titanium alloy with two different initial microstructures during heat treatment were determined. Result indicated that compared with coarse microstructure alloy, fine microstructure alloy developed finer microstructure, more unstable ω and α2 precipitates with much smaller size and lower volume fraction, and obtained better mechanical properties during heat treatment.

Microstructure and mechanical properties of heat-treated Ti-5Al-2Sn-2Zr-4Mo-4Cr

The effects of heat treatment parameters on the microstructure,and mechanical properties and fractured morphology of Ti-5Al-2Sn-2Zr-4Mo-4Cr with the equiaxed,bi-modal and Widmanst？tten microstructures were investigated.The heating temperatures for obtaining the equiaxed,bi-modal and Widmanst？tten microstructures were 830,890 and 920 °C,respectively,followed by furnace cooling at a holding time of 30 min.The volume fraction of primary α phase decreased with increasing the heating temperature,which was 45.8% at 830 °C,and decreased to 15.5% at 890 °C,and then the primary α phase disappeared at 920 °C during furnace cooling.The variation of volume fraction of primary α phase in air cooling is similar to that in furnace cooling.The increase in heating temperature and furnace cooling benefited the precipitation and growth of the secondary α phase.The equiaxed microstructure exhibited excellent mechanical properties,in which the ultimate strength,yield strength,elongation and reduction in area were 1035 MPa,1011 MPa,20.8% and 58.7%,respectively.The yield strength and elongation for the bi-modal microstructure were slightly lower than those of the equiaxed microstructure.The Widmanst？tten microstructure exhibited poor ductility and low yield strength,while the ultimate strength reached 1078 MPa.The dimple fractured mechanism for the equiaxed and bi-modal microstructures proved excellent ductility.The coexistence of dimple and intercrystalline fractured mechanisms for the Widmanst？tten microstructure resulted in the poor ductility.

Investigation on microstructures and mechanical properties of Mg-6Zn-0.5Ce-xMn(x=0 and 1)wrought magnesium alloys

The microstructure evolution and mechanical properties of Mg–6Zn–0.5Ce–xMn(x=0 and 1 wt.%)wrought magnesium alloys were researched,and the morphologies and role of Mn element in the experimental alloys were analyzed.The research shows that all of Mn elements form theα-Mn pure phases,which do not participate in the formation of other phases,such as theτ-phases.The mechanical properties of Mn-containing alloys in as-extruded and aged states are superior to Mn-free alloys.During the hot extrusion process,the dispersed fineα-Mn particle phase hinders the migration of grain boundaries and inhibits dynamic recrystallization,which mainly takes effect of grain refining and dispersion hardening.During the aging treatments,the dispersed fineα-Mn particle phase not only hinders the growth of the solution-treated grains,but also becomes the nucleation cores ofβ1 rod-like precipitate phase,which is conducive to increasing the nucleation rate of the precipitate phase.For the aged alloy,the Mn addition mainly takes effect of grain refining and promoting aging strengthening.

Microwave sintering effects on the microstructure and mechanical properties of Ti–51at%Ni shape memory alloys

Ti–51at%Ni shape memory alloys(SMAs) were successfully produced via a powder metallurgy and microwave sintering technique.The influence of sintering parameters on porosity reduction,microstructure,phase transformation temperatures,and mechanical properties were investigated by optical microscopy,field-emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD),differential scanning calorimetry(DSC),compression tests,and microhardness tests.Varying the microwave temperature and holding time was found to strongly affect the density of porosity,presence of precipitates,transformation temperatures,and mechanical properties.The lowest density and smallest pore size were observed in the Ti–51at%Ni samples sintered at 900°C for 5 min or at 900°C for 30 min.The predominant martensite phases of β2 and β19′ were observed in the microstructure of Ti–51at%Ni,and their existence varied in accordance with the sintering temperature and the holding time.In the DSC thermograms,multi-transformation peaks were observed during heating,whereas a single peak was observed during cooling;these peaks correspond to the presence of the β2,R,and β19′ phases.The maximum strength and strain among the Ti–51at%Ni SMAs were 1376 MPa and 29%,respectively,for the sample sintered at 900°C for 30 min because of this sample's minimal porosity.

Influence of semisolid forging ratio on the microstructure and mechanical properties of Ti14 alloy

The present work is focused on the microstructure and mechanical properties of Ti14 alloy with different semisolid deformation ratios during forging tests. The results revealed that the forging ratio had a significant effect on the precipitation of the alloy. Fewer plate-shaped Ti2Cu tended to precipitate on grain boundaries with higher forging ratios, and finally the plate-shaped Ti2Cu formed precipitate-free zones along grain boundaries with a forging ratio of 75%. The precipitation on grain boundaries was found to be controlled by a peritectic reaction. Large forging ratios accelerated the extrusion of liquid and resulted in less liquid along the prior grain boundaries, which reduced the peritectic precipitation in this region and formed precipitate-free zones during re-solidification. In addition, increasing the forging ratio could accelerate dynamic recrystallization, which is favorable for improving the semisolid formability. The tensile ductility increased with increasing forging ratio, and a mixed fracture mode, involving both cleavage and dimple fracture, was observed after forging with a forging ratio of 75%, which along grain boundaries during semisolid processing. is attributed to the presence of precipitate-free zones formed

Effects of Alloying Elements on the Microstructures and Mechanical Properties of Heavy Section Ductile Cast Iron

The effects of alloying elements on the as-cast microstructures and mechanical properties of heavy section ductile cast iron were investigated to develop press die material having high strength and high ductility. Measurements of ultimate tensile strength, 0.2% proof strength, elongation and unnotched Charpy impact energy are presented as a function of alloy amounts within 0.25 to 0.75 wt pct range. Hardness is measured on the broken tensile specimens. The small additions of Mo, Cu, Ni and Cr changed the as-cast mechanical properties owing to the different as-cast matrix microstructures. The ferrite matrix of Mo and Ni alloyed cast iron exhibits low strength and hardness as well as high elongation and impact energy. The increase in Mo and Ni contents developed some fractions of pearlite structures near the austenite eutectic cell boundaries, which caused the elongation and impact energy to drop in a small range. Adding Cu and Cr elements rapidly changed the ferrite matrix into pearlite matrix, so strength and hardness were significantly increased. As more Mo and Cr were added, the size and fraction of primary carbides in the eutectic cell boundaries increased through the segregation of these elements into the intercellular boundaries.

Effects of RE on Microstructures and Mechanical Properties of Hot-Extruded AZ31 Magnesium Alloy

Effects of rare earth (RE) additions on microstructure and mechanical properties of the wrought AZ31 magnesium alloy were investigated. The results show that, by adding 0.3%, 0.6% and 1.0% RE elements, the as-cast microstructure can be refined, and the as-cast alloys′ elongation and tensile strength can be improved. After extrusion, the alloy with 0.3% and 0.6% RE additions obtain a finer microstructure and the best mechanical properties, but the alloy with 1.0% RE addition has the coarse Al-RE compound particles in grain boundaries which decreased elongation and tensile properties. Usually, Rare earth (RE) elements were used to improve the creep properties of aluminium-containing magnesium pressure die cast alloys at elevated temperatures. In this paper, it is also found that the high temperature strength of extruded materials can be increased by RE elements additions.