Grain Size Of Alloy Research Articles

Experimental study and numerical simulation of α lamellar globularization for TC21 titanium alloy during multidirectional forging

Evolution of microstructure and the globularization mechanism of α lamellar for TC21 titanium alloy during multi-directional forging (MDF) were analyzed with the help of OM, SEM, EDS and TEM techniques, FE simulation was also used to observe the above process. The main conclusions are as follows: With the increase of temperature, forging cycle and single pass strain, the fraction of globularization of α lamellar gradually improved. The volume fraction of globularization of α lamellar achieves a high value about 85%, the average grain size of TC21 titanium alloy can be refined to 2 μm through MDFed at 910 °C with strain of 0.69 in 3 cycles. Forging cycle is the most key factor to obtain the ideal microstructure. Increasing temperature and MDFed pass can not only promote the fraction of DRX (dynamic recrystallization), but also achieve uniformity of deformation. The error between simulation and experiment is below 14%. DRX is the major globularization mechanism of the α lamellar during MDF. In the early stage of MDF process, the globularization mechanism is boundary splitting accompanied by CDRX (continuous dynamic recrystallization) and DDRX (discontinuous dynamic recrystallization), which is formed by the β phase into α lamella along the sub-grain boundaries. In the later stage of the process, the globularization mechanism is termination migration, which is caused by elements diffusion due to variant curvature of different position of α lamellar, while a slow process for globularization.

A Mg-6Y-3Zn-1Al Mg HPDC alloy having high thermal stability: Study of grain growth kinetics

The thermal stability and grain growth kinetics of a high-pressure die casting (HPDC) Mg-6Y–3Zn-1Al (WZA631, wt%) alloy with long-period stacking ordered (LPSO) phase is studied by subsequent annealing at different temperatures and time. The grain size of the as-cast and annealed samples is determined using the linear intercept method. It is found that grain size of WZA631 alloy hardly changes up to 450 °C, indicating the microstructure is thermally stable. The grain growth kinetics of WZA631 alloy between 450 °C and 550 °C is well described by the kinetic equation, Dn−D0n=kt. The grain growth exponent varies with temperature, ranging from n = 4.98 at 450 °C to n = 1.45 at 550 °C. The values of activation energy Eg are approximately 122.5 kJ/mol and 139.1 kJ/mol, respectively, for annealing temperature below and above 500 °C, which identifies the bulk diffusion to be the principal grain growth mechanism in the studied temperature range. The growth rate constant k at 450–500 °C is around 2–4 orders lower than other typical Mg alloys, suggesting the excellent thermal stability below 500 °C. The grain coarsening temperature TGC and softening temperature TS are all around 500 °C, implying the critical temperature related to the thermal stability of WZA631 alloy is ~500 °C. The microstructure evolution shows that LPSO network structure is a predominant factor inhibiting the grain growth of HPDC WZA631 alloy, and the dissolution of LPSO results in the variation of grain growth exponent.

Effect of thermomechanical processing on the mechanical properties of CuZn10 alloy

Abstract The effects of thermomechanical processing on the grain size, tensile strength, and strain rate of a CuZn10 alloy were investigated. Microstructures of thermomechanically treated samples were introduced using a scanning electron microscope. The relationships between the flow stress, reduction ratio, annealing temperatures, and strain rates were detected for determination of activation energies and optimized thermomechanical parameters. The effect of grain size on the mechanical properties was examined by tensile and microhardness tests. The typical fractographs of samples after tensile tests were examined using a scanning electron microscope. It was observed that the annealing temperature and aging time have significant effects on the optimum grain size. Mechanical properties of the thermomechanically treated samples were improved by strain rate, deformation ratio, annealing temperature, and aging time.

MgO-incorporated carbon nanotubes-reinforced Mg-based composites to improve mechanical, corrosion, and biological properties targeting biomedical applications

In this study, magnesium oxide (MgO) nanoparticles are incorporated on carbon nanotubes (CNTs) to reinforce Mg–3Zn–1Mn alloy (ZM31 alloy) by semi-powder metallurgy, followed by hot extrusion, with the purpose of improving the mechanical and biological properties of Mg-based alloy. The microstructural analysis of the nanocomposites indicated a reduction in grain size of Mg alloy with the incorporation of CNTs with a maximum reduction of 61% (ZM31/CNTs), with further reduction in grain size (68%) detected when MgO integrated CNTs composites (ZM31/MgO-CNTs). The compression characteristics of the composites indicate an increase in ultimate compressive strength of 36% and 44%, respectively, with the incorporation of CNTs and MgO-CNTs fillers, and the hardness of Mg alloy increases by 37% and 58%, respectively, with the incorporation of CNTs and MgO-CNTs fillers. The strengthening mechanisms of Mg alloy composites reinforced with MgO-CNTs were discussed. Furthermore, MgO bounded CNTs fillers decelerated the degradation rate of Mg-based alloys, whereas the introduction of CNTs to Mg alloy had a less significant effect. Besides, the ZM31/MgO-CNTs composite indicated superior cytocompatibility because of its lower corrosion rates. According to the overall results, the outstanding mechanical performance, appropriate corrosion characteristics, and good cytocompatibility of the ZM31/MgO-CNTs composites verified their potential in medical fields.

Effects of Sc Microalloying on Microstructure and Properties of As-Extruded Al-5Mg Alloy

Al-Mg alloys were fabricated by hot extrusion process after vacuum + argon-protected casting. The effects of Sc microalloying on microstructure and properties of as-extruded Al-5Mg alloy were studied. The results show that alloy 2 containing Sc is partially recrystallized during hot extrusion, resulting in the structure of alloy 2 consisting of 21.8% equiaxed recrystallized structure and 78.2% fine banding structure. The grain size of alloy 2 is about 5.31 μm, which is 83.3% finer than that of alloy 1 without Sc. The sum of the yield strength increments due to grain boundary strengthening (σGB) in alloy 2 is 103.59 MPa, where low angle grain boundary strengthening (σLAGB) is increased by a factor of 4.5, and high angle grain boundary strengthening (σHAGB) is increased by 73.4% compared to that of alloy 1. The addition of 0.2% Sc leads to an increase in the lattice strain and dislocation density of alloy 2, and the dislocation strength (σdis) increases to 41.85 MPa. The alloy 2 with Sc has a higher tensile strength of 380.7 MPa, which is 34.1% higher than that of alloy 1, but alloy 2 has a 46.2% reduction in elongation compared to alloy 1.

The role of solutes in grain refinement of hypoeutectic magnesium and aluminum alloys

The effect of solutes on grain formation has been studied over a century but is still under debating, simply because it is a very complex topic. This article focuses on the effect of dissolved solute on the growth, fragmentation of a dendrite and the resultant grain size. Experimental data on grain size in magnesium and aluminum alloys with various solute concentrations are collected and analyzed using phase diagram variables including Q, P, and ΔT. The physical meaning of each phase diagram variable is discussed. Curve fitting of the recently proposed two-parameter models with experimental data suggests that there is a clear correlation between the measured grain size and the solidification range of the alloy over the entire range of the hypoeutectic composition. Such a trend of grain size vs. ΔT is closely related to the grain refining mechanisms operating under relevant experimental conditions. A critical review of the grain refining mechanisms indicates that the mechanisms associated with the dendrite fragmentation are operating under the conditions where convection is substantial in the melt during its solidification.

Effect of CeO2 and VC co-doping on the microstructure and properties of WC-10Co cemented carbide

Combining spray drying and in-situ synthesized technology, WC-10Co cemented carbides with uniform composition was prepared by vacuum sintering to investigate the effects of different CeO2 contents (0 wt%, 0.5 wt%, 1 wt%, 2 wt%, 4 wt%) as well as co-doping with CeO2 and VC on the microstructure and mechanical properties. With increasing CeO2 addition from 0 wt% to 0.5 wt%, the WC grain size decreased from 0.79 ± 0.35 μm to 0.62 ± 0.24 μm. The hardness, fracture toughness and transverse rupture strength (TRS) of the alloy with 0.5 wt% CeO2 all reached the maximum values of 1752 ± 28 HV30, 18.50 ± 0.35 MPa·m1/2 and 2245 ± 35 MPa, respectively, which indicated that the mechanical properties of cemented carbide could be simultaneously improved by adding 0.5 wt% CeO2 to refine the WC grains. However, as the CeO2 content increased to 4 wt%, the hardness gradually decreased, while the fracture and TRS all slightly decreased first and then tended to be stable. Moreover, the corrosion resistance of alloys first increased and then decreased with the increase of CeO2 content. The 0.5 wt% CeO2 alloy had the best corrosion resistance. After adding 0.5 wt% VC, the grain size of alloys became smaller and distribution of Co binder was more uniform. Compared to the samples with only added CeO2, the alloy with co-addition of 0.5 wt% CeO2 and 0.5 wt% VC exhibited the best comprehensive mechanical properties. The hardness, fracture toughness and TRS of the alloy with co-addition of 0.5 wt% CeO2 and 0.5 wt% VC were 1987 ± 44 HV30, 16.10 ± 0.34 MPa·m1/2 and 2023 ± 78 MPa, respectively.

Effect of micro-alloyed Ce on the microstructure evolution and mechanical properties of rolled Mg–0.6Al–0.5Mn–0.2Ca alloy sheets

In this study, the effect of minor Ce addition (0, 0.1, and, 0.3 wt.%) on the microstructure evolution and mechanical properties of rolled Mg–0.6Al–0.5Mn–0.2Ca (AMX100) alloy sheets is systematically investigated under different annealing processes. With 0.1 wt.% Ce addition, partial Al8Mn5 phases turn into Al8Mn4Ce. With 0.3 wt.% Ce addition, the number of the Al8Mn4Ce further increases and the Al–Ce phases are observed. The single-stage annealed alloys exhibit similar uniform fine-grained structures (∼6 μm) regardless of the Ce content, while the grain sizes of the two-stage annealed alloys increase obviously (∼10.9–11.9 μm). Especially, the abnormal grain growth occurs in the two-stage annealed AMX100-0.3Ce alloy. After the aging treatment, the yield strength (YS) of the two-stage annealed alloys is increased by ∼25–45 MPa, which is greatly higher than that of the single-stage annealed alloys (∼1–8 MPa). Note that the two-stage annealed AMX100–0.1Ce alloy displays a significant age-hardening response with the ultimate tensile strength (UTS) of ∼272 MPa and the elongation to failure (EF) of ∼14%, which is attributed to the formation of Al and Ca enriched Guinier-Preston (G.P.) zones. This work sheds light on the design and fabrication of low-cost dilute magnesium alloys with admirable age-hardening ability.

Effect of an Al-TiO2-C-Er2O3 Refining Agent on the Corrosion Resistance of a ZL205 Alloy

In this study, a new type of Al-TiO2-C-Er2O3 refiner was prepared by exothermic dispersion, and the refiner was added to a ZL205 alloy to investigate the effect of the Al-TiO2-C-Er2O3 refiner on the refinement effect and corrosion resistance of the ZL205 alloy. The results reveal that, with the increase in the Er2O3 content, the refining effect is first enhanced and then reduced. The best refining effect of the Al-TiO2-C-Er2O3 refiner was observed by the addition of 6% Er2O3, which refined the grain size of the ZL205 alloy from 147 μm to 103.9 μm, and the grain size was 72% of the ZL205 alloy. The addition of the Al-TiO2-C-Er2O3 refiner led to the improved bias agglomeration of the CuAl2 phase at the grain boundaries in ZL205 and reduced the corrosion sensitivity of the alloy; moreover, the α-Al nucleation temperature of the ZL205 alloy increased, the crystallization interval ΔT of the CuAl2 phase increased from 7.4 °C to 9.3 °C, corresponding to an increase of 1.9 °C, and the self-corrosion current density (icorr) of the ZL205 alloy was reduced from (2.83 × 10−5 A/cm2) to (6.26 × 10−6 A/cm2), a decrease of 77.8%; the polarization resistance (R1 + R2) was 1808.62 Ω·cm2 in comparison with that of the original ZL205 alloy (480.42 Ω·cm2), corresponding to a 276.7% increase.

Effect of rotating shear extrusion on the microstructure, texture evolution and mechanical properties of Mg-Gd-Y-Zn-Zr alloy

In this paper, the Mg-9Gd-4Y–2Zn-0.5Zr (wt%) alloy after one pass of upsetting and extrusion was subjected to the rotating shear extrusion (RSE) method and backward extrusion (BE) method at 420 °C. Compared with the BE method, torsion deformation and shear deformation were synthetically introduced to the RSE process. The RSE technique had the advantages of a low forming load, large strain and more sufficient deformation. The results demonstrated that the RSE method had more advantages than the BE method in terms of grain refinement and mechanical performance improvement. The average grain size of the RSEed alloy was refined from ~22 µm of the original alloy to ~8.5 µm. In addition, the proportion of dynamic recrystallization (DRX) increased from ~56% of the original alloy to ~83% via the RSE process. The degree of fragmentation of the lamellar and block-shaped LPSO phases in the RSEed alloy was more intensive than that of the BEed alloy, and the particle phase distribution among the crystal grains was more uniform. The RSEed alloy presented a single texture and a strong [2−1−10] orientation component and effectively weakened the texture intensity. The ultimate tensile strength (UTS), tensile yield strength (TYS) and elongation (EL) of the RSEed sample were 350 MPa, 258 MPa and 17%, respectively. Compared with the BEed sample, the mechanical properties of 325 MPa (UTS), 240 MPa (TYS) and 12% (EL) had higher strength and toughness. After the same T5 (200 ℃/90 h) heat treatment, the mechanical properties of the RSEed sample could reach 420 MPa (UTS), 280 MPa (TYS) and 13% (EL), while BEed sample were 371 MPa (UTS), 273 MPa (TYS) and 10% (EL). Additionally, compared with the BEed alloy, the mechanical properties of the RSEed alloy are better due to finer grains, broken LPSO phases, dispersed particle phases and texture modification. • The RSE process could be effectively reduced the forming load and produce more strain than BE. • The LPSO phases are broken to a greater extent and granular phases are more distributed during the RSE process. • The RSE method could greatly change the texture and orientation of the initial alloy. • The RSE method could improve the strength and toughness of the alloy.

Optimizing low frequency electromagnetic parameters by controlling the distribution of boron in FeSiAl alloy

Flaky FeSiAlB alloy powders were prepared by melting, quenching and milling. The effects of boron on the microstructure of FeSiAl alloy powders, the element distribution on the grain boundary of parent alloy, and the room temperature tensile properties of as-quenched sheet were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS) and tensile testing machine, respectively. With the addition of boron, the grain size of the master alloy was refined, and the tensile strength of the quenched sheet at room temperature was significantly improved. And obvious boron-rich regions were observed at grain boundaries. Soft magnetic properties were measured by vibrating sample magnetometer (VSM). Based on the electromagnetic parameters measured by vector network analyzer (VNA), the microwave absorption properties of flaky powder were calculated. The particles with high flake have high permittivity and permeability. Reflection loss (RL) shows that when B content amount was 0.06 at%, the absorption performance of the original FeSiAl absorbing material is improved in L and S bands, and the absorption peak moves from high frequency to low frequency. Excessive B element will lead to impedance mismatch, and the absorption performance in L and S bands will gradually decrease. For FeSiAlB flaky powder with 0.06 at % B content, the RL is −10.7 dB at 1.9 GHz and the matching thickness is 3 mm.

Corrosion behaviors related to the microstructural evolutions of as-cast Al0.3CoCrFeNi high entropy alloy with addition of Si and Ti elements

In this work, the electrochemical potentiodynamic polarization and impedance spectroscopy analysis were used to investigate the corrosion behaviors related to microstructural evolutions of Al0.3CoCrFeNiSix and Al0.3CoCrFeNiTix HEAs in the NaCl solution. The results presented that addition of Si promoted the formation of BCC phase, which was regarded as a micro-anode to prevent FCC phase as a micro-cathode from being corroded. While the volume fraction of BCC phase increased to enhance the corrosion resistance of Six alloys with increasing Si content. Furthermore, the reduction in the grain sizes of Six alloys with increasing Si content could also improve corrosion resistance of the alloys. Therefore, the corrosion resistance of Six alloys was increased with increasing Si content. Addition of Ti with a high corrosion resistance of Clˉ caused the reduction in the grain sizes of Tix alloys, which can improve the corrosion resistance of alloys. However, the high Ti content can destroy the corrosion resistance of the alloys due to the formation of a large amount of precipitated phases. Therefore, as Ti with atomic percentage be equal to that of Al can effectively eliminate the negative influence of precipitated phases and microstructure on the corrosion resistance of alloys, meaning the Ti0.3 alloy had the best corrosion resistance in Tix alloys. The analysis of X-ray photo-electron spectroscopy (XPS) identified that the contents of oxidized Cr3+ and Fe3+ in the passive film are the main contribution to improve the corrosion resistance of Six alloy. And the contents of oxidized Cr3+ and Ti4+ in the passive film are the main contribution to improve the corrosion resistance of Tix alloy.

Study on Sc Microalloying and Strengthening Mechanism of Al-Mg Alloy

In this study, Al-Mg alloys were prepared by vacuum + argon-protected casting. The effects of Sc microalloying on the microstructure and mechanical properties of Al-Mg alloy were studied. The strengthening mechanism of Al-Mg alloy with Sc was discussed. The results show that the average grain size of as-cast Al-Mg alloy with Sc reaches 36.07 μm, which is 74.4% smaller than that of alloy 1 without refiner and 32.0% of alloy 2 with 0.15% Ti. The alloy with Sc has excellent comprehensive mechanical properties, with a tensile strength of 274 MPa and an elongation of 29.67%, and its tensile strength is 10.6% higher than alloy 1 and 7.9% higher than alloy 2. There exist two kinds of fine particles in as-cast Sc-containing Al-Mg alloy, nucleated particles Al3Sc, and dispersed second-phase particles Al3(Sc, Ti). The main strengthening mechanisms of the as-cast Al-Mg alloy with Sc reveal the solid solution strengthening of Mg and the fine-grain strengthening effect caused by Sc, accounting for 57.7% and 23.9% to strengthening contribution, respectively.

Strengthening mechanism and biocompatibility of degradable Zn-Mn alloy with different Mn content

In this study, the mechanical properties and biocompatibility of Zn-Mn alloys with different Mn contents have been investigated. The results show that the grain size of the Zn-Mn alloys decreases with the increasing Mn content and the second phase MnZn13 precipitates when Mn content is over 0.3 wt%. The elongation increases with the increase of Mn content while Zn-0.3Mn achieves maximum yielding strength and tensile strength ultimate tensile strength. The mechanical properties are dominated by solid solution effect when the Mn content is lower than 0.15 wt% while the effects of grain refinement and precipitation strengthening become remarkable with the Mn content increasing to 0.3 wt%. When the Mn content increases to 0.5 wt%, the tensile strength of the alloy remains unchanged while the elongation is further increased by grain boundary sliding due to further grain refinement and reduced dislocation density. Immersion tests show decreasing Zn2+ and increasing Mn2+ concentrations in extract, leading to lower cytotoxicity and better cell proliferation. The Zn-0.5Mn alloy exhibits a maximum comprehensive mechanical property as well as in vitro / in vivo biocompatibility with an implication for biomedical implant applications.

Improving the high temperature mechanical performance of Cu–Cr alloy induced by residual nano-sized Cr precipitates

The mechanical performance of Cu–Cr alloy severely deteriorates at high temperatures due to the Cr precipitates coarsening rapidly or dissolving in Cu matrix again. This study achieved the supersaturated solid solution Cu-5wt%Cr alloy (S1) with Cr solubility of 0.94 wt% by combining mechanical alloying and spark plasma sintering. The effect of residual Cr precipitates on the high temperature hardness, softening resistance and microstructures were investigated. The results showed that S1 alloy exhibited an excellent hardness of 106.27 HV at 500 °C, 23.14% higher than the common sample. The softening temperature of S1 alloy is 800 °C (0.74Tm), and the average grain size of S1 alloy annealed at 800 °C is 0.69 μm, which increased by only 0.11 μm. The microstructural evolution showed that the high thermal stability is mainly attributed to two kinds of residual Cr precipitates in the matrix. The larger ones act as obstacles to inhibit the motion of Cu grain boundaries, and the fine precipitates disperse in Cu matrix to fix the dislocations. Combining these two types of residual Cr precipitates act as very powerful obstacles to inhibit the motion of dislocations and grain boundaries. Also, the increment in yield strength at elevated temperature (300–700 °C) deduced from the residual Cr precipitates strengthening ranges from 320 MPa to 337 MPa.

Effects of Laser Surface Remelting on Microstructure and Corrosion Properties of Mg-12Dy-1.1Ni Alloy

Effects of laser surface remelting (LSR) on microstructure and corrosion properties of as-cast Mg-12Dy-1.1Ni (wt.%) alloy were investigated. The as-cast alloy was mainly composed of α-Mg, lamellar Mg12DyNi phase with an 18R-long period stacking order (LPSO) structure and Mg24Dy5. After LSR treatment, fine and compact 18R-LPSO phase reprecipitated on dendrite boundaries as a continuous network. In addition, the volume fraction of the LPSO phase remarkably increased to 34.9% and the grain size of as-cast alloy was refined to ca. 4 μm. Electrochemical and immersion tests indicated that the LSR-treated alloy exhibited a lower weight loss rate (2.8 ± 0.2 mg/cm2/h) and corrosion current density (160.1 ± 20.7 μA/cm2, and of 37% reduction after LSR) than the as-cast alloy in 0.1 M NaCl solution. The improved corrosion resistance of the LSR alloy was mainly ascribed to the grain refinement and continuous distribution of 18R-LPSO phase on dendrite boundaries.

Electrochemical Corrosion Resistance of Mg Alloy ZK60 in Different Planes with Respect to Extrusion Direction

The electrochemical corrosion resistance of a Mg-Zn-Zr alloy, ZK60, in different planes with respect to the extrusion direction was investigated in 3.5 wt% NaCl. The motivation of this study lies in the influence of extrusion on the grain size, texture and precipitation characteristics of magnesium alloys, and the profound role of these characteristics in the corrosion resistance of the alloys. Corrosion resistance was found to be considerably superior in the plane transverse to the extrusion direction (TD) than in the extrusion direction (ED) or normal to the extrusion direction (ND). The difference in the corrosion resistance was attributed to the variations in microstructural features in the TD, ED and ND directions.

Effects of Sr additions on the microstructural stability and mechanical properties of a cast Mg–4Zn alloy

The effects of Sr additions (0.3, 0.6 and 0.9 wt%) on the microstructural evolution, thermal stability, and mechanical properties of a cast Mg–4Zn alloy were investigated. The extent of grain growth and stability of the intermetallic compounds were studied by optical and scanning electron microscopy (SEM), respectively. Mechanical properties of the studied alloys were evaluated by shear punch testing (SPT) method and also the hardness test. Hardness and shear strength of the base alloy were increased by Sr additions in the as-cast condition, due to the grain refinement effect of Sr and also presence of the Sr-containing Mg17Sr2 and Mg70Zn25Sr5 precipitates. However, the optimum amount of Sr was determined to be 0.3 wt%, above which no further improvement in the shear strength of the as-cast alloys was observed, due to the coarsening of the precipitates. The obtained microstructural results indicated that while both of the base and Sr-containing alloys have appropriate thermal stability at 330 °C, the grain size of the base alloy increased significantly and also the Mg4Zn7 particles were dissolved in the matrix after annealing treatment at 400 °C for 96 h, resulting in considerable decrease in the shear strength. However, grain growth was trivial in the Sr-containing alloys, due to the presence of thermally stable Mg17Sr2 particles. Accordingly, the Sr addition was found to be beneficial to improve the stability of the microstructure and mechanical properties of the Mg–4Zn alloy.

Effects of Magnetic Abrasive Finishing on Microstructure and Mechanical Properties of Inconel 718 Processed by Laser Powder Bed Fusion

Surface finishing is challenging in the context of additively manufactured components with complex geometries. Magnetic abrasive finishing (MAF) is a promising surface finishing technology that can refine the surface quality of components with complex shapes produced by additive manufacturing. However, there is insufficient study regarding the impact of MAF on microstructure–property relationships for additively manufactured builds, which is critical for evaluating mechanical performance. In this work, we studied the effects of different combinations of MAF and heat treatment steps on the microstructure–property relationships of Inconel 718 superalloys made by laser powder bed fusion (LPBF). The application of MAF was found to significantly reduce the surface roughness and refine the grain size of aged alloys. Moreover, MAF was able to increase the alloy elongation, which could be further influenced by the sequence of MAF and different heat treatment steps. The highest elongation could be achieved when MAF was performed between homogenization and aging processes. This work indicates that an effective combination of surface finishing and heat treatment is critical for the improvement of alloy performance. Furthermore, it demonstrates a promising solution for improving the performance of LPBF Inconel 718 by integrating MAF and heat treatment, which provides new perspectives on the post-processing optimization of additively manufactured alloys.

The formation mechanism of micro-nano secondary phase in solid-liquid doped TZM alloy

Among the various secondary phases distributed in the TZM (Titanium-Zirconium-Molybdenum) alloy matrix, the ones that can play a strengthening role are often those with a particle size smaller than 1 μm. In this study, titanium sulfate, zirconium nitrate, and fructose were used as raw materials. The TZM alloy with uniform distribution and an average secondary phase particle size of 940 nm (hereinafter referred to as MN-TZM alloy) was prepared through a solid-liquid doping preparation process. The thermodynamic calculation reveals the formation mechanism of the micro-nano-level secondary phase in the MN-TZM alloy. Thermogravimetric analysis (TG-DSC, TG-MS) and transmission electron microscope (TEM) confirmed the calculation results. The generation process of the micro-nano secondary phase evolution can be divided into four parts. The first stage is the process of solute dissolution at room temperature. In the second stage, doping and drying process take place below 100 °C. Third, reduction and secondary phase precursor incubation processes occur from 100 to 700 °C. Fructose decomposes (100 °C) to obtain organic carbon and water. The decomposition of zirconium nitrate (100 °C) yields NH 3 , H 2 O, ZrO 2 and Zr, while the titanium sulfate decomposes directly at 200– 242 °C to obtain SO 2 , H 2 O, TiO 2 and Ti. In the last stage, the secondary phase nucleates and grows up (700– 1800 °C). A large variety of micro-nano-scale and even nano-scale secondary phase particles have been discovered, including TiO 2 , ZrO 2 , ZrC and TiC. These observations provide necessary information for tracing back the secondary phase precipitation mechanism in the manufacturing process of high-performance molybdenum alloys. • The average grain size of MN-TZM alloy is 940 nm. • The micro-nano secondary phase reduces the average grain size of TZM alloy by 26%. • TZM alloy was prepared from titanium sulfate, zirconium nitrate, fructose and molybdenum powder for the first time. • The formation mechanism of micro-nano secondary phase in TZM alloy was clarified.