Homogenization Heat Treatment Research Articles

Development of a 7000 series aluminium alloy suitable for laser-based Additive Manufacturing

High strength aluminium alloys are of significant interest for laser-based Additive Manufacturing as they can provide a high specific strength but have limited assembly possibilities due to poor weldability and the presence of large intermetallic particles challenging the conventional manufacturing route. Increasing the geometrical freedom by enabling their use with laser-based Additive Manufacturing would create new possibilities. This study investigates the possibilities of using an aluminium 7000 series alloy with Laser Powder Bed Fusion (L-PBF) and secondly for comparison with Direct Energy Deposition (DED). The chemical composition targets 5.1 – 6.1 wt% Zn and 2.1 – 3.9 wt% Mg. The level of Zn and Mg in the powder was increased to 10 wt% Zn and 3 wt% Mg to compensate for the expected evaporation during the laser-based AM process and guarantee a sufficient Zn and Mg content for precipitation strengthening. Solidification cracking in the initial alloy composition was resolved by the addition of 1 wt% Zr and 1 wt% V. For L-PBF, a study of the impact of the laser spot size showed a larger spot size is beneficial to improve the process stability. A study of the capability of preheating and of slowing down the process showed both further improve the process stability as well which is required to manufacture successfully larger parts to characterise the quasi-static tensile properties. For optimal process parameters for a fast process, meaning a scan speed of 700 mm/s, a yield stress of 425 ± 7 MPa and an ultimate tensile strength of 442 ± 5 MPa was obtained after a homogenisation and ageing heat treatment. In the as built state, the strength was significantly lower. For optimal process parameters for a slow process, meaning a scan speed of 250 mm/s, a yield stress of 398 ± 11 MPa and an ultimate tensile strength of 440 ± 16 MPa were obtained in as built state. For DED the mechanical properties of the alloy showed to be significantly dependent on process parameters. An excessive energy input results in more Zn and Mg evaporation and decreased cooling rates. Such parameters also impact the process stability of DED throughout the build cycle. Limiting the energy input resulted in dense samples and stable build cycles which after a heat treatment to peak ageing reached a yield stress of around 400 MPa and an ultimate tensile stress of around 440 MPa in the X- and Z-direction.

Homogenization Heat Treatment and Tribological Properties of In Situ Alloyed NiTiCu by Laser Powder‐Bed Fusion

In situ alloying by additive manufacturing (AM) of premixed powders has been recognized as a promising low‐cost method for creating complex parts for biomedical implants, in which homogenization heat treatment is a critical concern in this technology. Also, as promising implant materials, their tribological properties under dry and lubrication conditions are significantly concerned with evaluating the functionalities of 3D printing. This work preliminarily addresses these two concerns with the laser powder‐bed fusion (LPBF) 3D‐printed nickel titanium copper (NiTiCu) alloy using three homogenization heat treatments and ball‐on‐disc wear tests under dry and NaCl‐lubricated conditions. It is found that to achieve sufficiently good microstructural homogeneity with low porosity, a temperature of 800 °C and a duration of 5 h is needed. Despite the promising outcome, analysis of the results revealed that all heat treatments led to the formation of a secondary phase identified as Ti2(Ni,Cu), which induced two‐step phase transformations. Thus, further studies on the optimization of the postprocessing techniques are required. The heat‐treated alloy resulting in the most favorable properties is selected for tribological testing. AM and the addition of Cu are observed to enhance the wear resistance of the alloy under lubrication conditions.

Intense pulsed light-induced millisecond selective heat treatment for high-performance silicon anodes

Silicon, which is gaining prominence as a potential anode material, exhibits long-term cycle stability issues owing to volume changes during cycling. This study presents a meticulously designed Si anode that employs intense pulsed light (IPL) technology to simultaneously reduce carbon additives and construct an effective carbon quantum dot (CQD)-derived binder system. IPL, as a light-material interaction technique, offers a novel approach for selective heat treatment with remarkably short processing durations on the order of milliseconds. By comprehensively considering the geometric structure, optical characteristics, and thermal properties of each electrode component, heat transfer bridge (HTB) materials are introduced to ensure a homogeneous depth-directional heat treatment and to minimize binder decomposition in the IPL process. By employing HTB materials, the binder can reach a controlled target temperature for the condensation reaction between poly (acrylic acid) and the CQDs. Simultaneously, higher heat generation in the conductive carbon than in the binder leads to selective additional carbon reduction. This unique approach provides selective heat treatment, which cannot be achieved using conventional methods, resulting in a Si anode with excellent cyclic stability and rate capability. The versatility of the IPL technology is further demonstrated by applying it to relatively inexpensive Si microparticles.

Effects of Fe addition on the mechanical and corrosive properties of biomedical Co-Cr-W-Ni alloys for balloon-expandable stents

Co-20Cr-15W-10Ni (mass%, CCWN) alloy is extensively used as a platform material for balloon-expandable stents. In this study, the mechanical properties of CCWN alloy are improved following the addition of Fe, and the effects of Fe addition on the mechanical and corrosive properties of the alloy are investigated. As-cast specimens were fabricated by adding pure Fe to a commercially available CCWN alloy (base alloy) such that the resulting alloys contained 4, 6, and 8 mass% Fe. The as-cast specimens were subjected to homogenization heat treatment at 1523 K for 7.2 ks and then hot-forged at 1473 K (as-forged specimens). The as-forged specimens were cold-rolled at a reduction rate of 30% and heat-treated at 1473 K for 300 s (recrystallized specimens). The matrix of the recrystallized base- and Fe-containing alloys consisted of a single γ (face-centered cubic)-phase. The Fe-added alloys revealed precipitates composed of the η-phase (M6X-M12X-type phase, M: metallic element, X: C and/or N). The average grain size of the recrystallized base and Fe-added alloy specimens was approximately 34 μm and the amount of added Fe had no significant effect on the static recrystallization behavior of the resulting alloys. Alloys containing 6 mass% or more Fe showed improvements in strength and ductility compared with the base alloy. When the Fe-added alloys were compared, their strength decreased whereas their ductility increased when the added Fe increased. Because Fe acts as a γ-phase-stabilizing element for Co, Fe addition increases the stacking fault energy of the base alloy, resulting in the formation of the ε (hexagonal close-packed)-phase owing to the suppression of strain-induced martensitic transformation (SIMT), and improvements in ductility. No deterioration in corrosion resistance was observed following the addition of up to 8 mass% Fe to the base alloy. Based on these results, the addition of Fe to CCWN alloy may be considered an effective method to improve its mechanical properties, especially ductility, without impairing its corrosion resistance. The results of this study will be useful for the future development of Ni-free Co-Cr alloys for next-generation, small-diameter stents.

Laser directed energy deposition of Alnico-8H from blended elemental powders: Effect of nickel increase on magnetic properties

Alnico-8H (14 wt% Ni) and Alnico-8H (19 wt% Ni) were additively fabricated from a blend of elemental powders with compositions (in wt.%) of 38Co-29Fe-14Ni-8Al-8Ti-3Cu and 33Co-29Fe-19Ni-8Al-8Ti-3Cu, respectively, using laser-directed energy deposition technique. Post additive fabrication both compositions were subjected to homogenization heat treatment at 1250 °C for 30 min and magnetic annealed at 650 °C under 2.5 T magnetic field for 60 mins (1 hr). X-ray diffraction was employed for studying the phase evolution. Scanning and transmission electron microscopes were utilized for characterization of Alnico alloys. The targeted compositions for Alnico-8H (14 wt% Ni) and Alnico-8H (19 wt% Ni) were nearly achieved in the L-DED processed samples. homogenization at 1250 °C, followed by magnetic annealing at 650 °C, resulted in an increase in grain size. The transmission electron microscopy revealed the presence of ferromagnetic α1 and paramagnetic α2 phases in the magnetic annealed microstructure. The increase in Nickel content from 14 to 19 wt% resulted in increase in coercivity (242 to 255 Oe), remanence (4437 to 8659 G), and maximum energy product (BHmax) (0.27 to 0.53 MGOe).

Influence of forging pretreatments on microstructure evolution and surface roughness of Al 6061 alloy

Achieving ultra-smooth surfaces is the goal of aluminum optical manufacturing. Under certain processing conditions, improving the microstructure of aluminum and understanding its relationship with surface roughness requires systematic study. The grain structure and various types of second-phase particles are of paramount importance. This study analyzed the microstructure of 6061 alloy after undergoing severe plastic deformation under various processing conditions followed by T6 homogenization heat treatment. Utilizing a white light interferometer, a comparative analysis of the surface roughness was conducted on specimens that underwent single-point diamond turning to achieve a mirror finish. The assessment of surface roughness on machined surfaces is solely based on white light interferometry. The analysis and discussion focus on the effects of phases (causing scratches and voids), the grains and grain boundaries. Experimental findings signify: the grain size, grain boundary and residual second phase can both influence the surface quality, the increase in deformation temperature and accumulated strain both facilitate the dissolution and fragmentation of the secondary phases. However, they also contribute to some extent to grain growth, resulting in a minimum secondary phase area fraction of 0.87% and grain sizes reaching 147.8 μm. Subsequent heat treatments, while effective in reducing the negative impact of the phases, reveal noticeable step-like structures affecting the quality of surface roughness, with the lowest obtained Ra value being 0.8 nm. A proposed pretreatment method in cleaner ingot processing with lower alloy element content addresses the trade-off between reducing phases and controlling grain growth, aiming to achieve improved surface roughness, promoting the application of polycrystalline aluminum alloys in the field of optics manufacturing.

Effect of post-deposition heat treatments on the microstructure and tensile properties of wire-fed electron beam directed energy deposition GH4169 Ni-based alloy

The microstructure and tensile properties of GH4169 alloy fabricated by wire-fed electron beam directed energy deposition (EB-DED) were investigated in both as-deposited (As-Dep) and homogenization plus double aging heat treatment (HA) condition. The results show that thermal cycling caused an aging effect in the As-Dep samples, resulting in the precipitation of the γ’/γ” phases in close proximity to the Laves phase. The dissolution behavior of Laves phase in GH4169 alloy at various homogenization heat treatment temperatures and holding times was studied. Based on experimental results and Johnson-Mehl-Avramie-Kolmogorov (JMAK) analysis, the dissolution activation energy of Laves phase was calculated as 218.2 kJ/mol. The heat treatment regime utilized in HA treatment consisted of 1150 °C × 60 min/WC + 720 °C × 8 h/FC to 620 °C × 8 h/WC. After HA treatment, most of the Laves phases were dissolved and the γ’/γ” phases were precipitated. The mechanical properties of HA samples are superior to those of As-Dep samples. The morphology, distribution and evolutionary mechanism of the Laves phase, γ’/γ” phases are discussed and analyzed.

Conversion of cobalt from spent LIBs to Co3O4 electrode material for application in supercapacitors

ABSTRACT The cathode material of lithium-ion batteries (LIBs) is endowed with valuable metals, such as cobalt. The improper treatment of these batteries pollutes the environment and causes enormous resource waste. Therefore, the recovery of valuable metals from spent LIBs has attracted widespread attention. In this study, Co3O4 electrode materials were prepared by a simple homogeneous precipitation method and heat treatment using a leaching solution of spent LIBs-positive electrode material as the cobalt source. The crystal structure and morphology of the products were examined at different annealing temperatures, and their electrochemical performance was analyzed. The results show that low-temperature annealing contributes to grain refinement. The Co3O4 material prepared at 300°C annealing temperature has a rod-like structure with distinct pores and a specific surface area of 58.98 m2 g−1. Furthermore, electrochemical performance testing reveals that Co3O4 prepared at 300°C displays the best electrochemical performance as an electrode material, with a specific capacitance of 97.93 F g−1 and a cycle retention rate of 79.12% after 500 charge–discharge cycles. These findings demonstrate the feasibility of recycling valuable metal cobalt from spent LIBs cathode materials to produce Co3O4 materials for use as supercapacitor electrode materials, opening up new avenues for the recycling and utilisation of spent LIBs.

Homogenization Heat Treatment for Enhancing Corrosion Resistance and Tribological Properties of the Al5083-H111 Alloy.

In this study, an Al5083-H111 alloy was divided into two different parameters without heat treatment and by applying homogenization heat treatment. In the homogenized Al5083 sample, it helped to make the matrix structure more homogeneous and refined and distribute intermetallic phases, such as the Al-Mg phase (Mg2Al3) and Al-Fe phases, more evenly in the matrix. There was an increase in the hardness of the homogenized sample. The increase in hardness is due to the material having a more homogeneous structure. Corrosion tests were applied to these parameters in NaCl and NaOH. It is observed that Al5083 samples before and after heat treatment show better corrosion resistance and less weight loss in NaOH and NaCl environments. It was observed that the fracture resistance of the alloy in the NaOH solution was lower, and the weight loss was higher than the alloy in the NaCl solution. Wear tests were performed on two different parameters: a dry environment and a NaOH solution. Since the NaOH solution has a lubricating effect on the wear surface of the sample and increases the corrosion resistance of the oxide layers formed, the wear resistance of the alloys in dry environments was lower than the wear resistance of the alloys in the NaOH solution. A hydrogen evolution test was performed on the samples in the NaOH solution, and the results were recorded. Hydrogen production showed higher hydrogen output from the homogenized sample. Accordingly, a higher corrosion rate was observed.

Additive manufacturing of duplex stainless steel by DED-LB/M and PBF-LB/M – process-material-property relationships

PurposeAdditive manufacturing (AM) of duplex stainless steels (DSS) is still challenging in terms of simultaneously generating structures with high build quality and adequate functional properties. This study aims to investigate comprehensive process-material-property relationships resulting from both laser-directed energy deposition (DED-LB/M) and laser powder bed fusion (PBF-LB/M) of DSS 1.4462 in as-built (AB) and subsequent heat-treated (HT) states.Design/methodology/approachCuboid specimens made of DSS 1.4462 were generated using both AM processes. Porosity and microstructure analyses, magnetic-inductive ferrite and Vickers hardness measurements, tensile and Charpy impacts tests, fracture analysis, critical pitting corrosion temperature measurements and Huey tests were performed on specimens in the AB and HT states.FindingsCorrelations between the microstructural aspects and the resulting functional properties (mechanical properties and corrosion resistance) were demonstrated and compared. The mechanical properties of DED-LB/M specimens in both material conditions fulfilled the alloy specifications of 1.4462. Owing to the low ductility and toughness of PBF-LB/M specimens in the AB state, a post-process heat treatment was required to exceed the minimum alloy specification limits. Furthermore, the homogenization heat treatment significantly improved the corrosion resistance of DED- and PBF-processed 1.4462.Originality/valueThis study fulfills the need to investigate the complex relationships between process characteristics and the resulting material properties of additively manufactured DSS.

Hot Deformation Constitutive Analysis and Processing Maps of Ultrasonic Melt Treated A5052 Alloy.

Hot deformation constitutive analysis and processing maps of ultrasonic melt treated (UST) A5052 alloy were carried out based on a hot torsion test in this study. The addition of the Al-Ti master alloy as a grain refiner with no UST produced a finer grain size than the UST and pure Ti sonotrode. The Al3Ti phase particles in the case of the Al-10Ti master alloy acted as a nucleus for grain refinement, while the Ti atoms dissolved in the melt from the sonotrode were considered to have less of a grain refinement effect, even under UST conditions, than the Al3Ti phase particles in the Al-Ti master alloy. The constitutive equations for each experimental condition by torsion test were derived. In the processing maps examined in this study, the flow instability region was not present under UST in the as-cast condition, but it existed under the no UST condition. The effects of UST examined in this study are considered as (i) the uniform distribution of Ti solutes from the sonotrode and (ii) the reduction of pores by the degassing effect. After the homogenization heat treatment, most instability regions disappeared because the microstructures became uniform following the decomposition of intermetallic compounds and distribution of solute elements.

Heat Treatment Influence on the Cavitational Erosion Zn-Mg Behavior Used for Biomedical Applications

Recent research in the medical field of temporary implants refers to the development of new biodegradable alloys, which are simultaneously subject to aggressive conditions of pressure fluctuations exerted in blood vessels. Both zinc and magnesium are biocompatible metallic materials, but also biodegradable. The present work approaches a new alloy from the Zn-Mg system, elaborated within the Polytechnic University of Bucharest, on which cavitational erosion tests were performed. It was followed the effect of applying the homogenization heat treatments of cast alloy, at different temperatures and maintenance durations (300°C and 400°C, each with a maintenance of 5h and 10 h) on the behavior at the vibratory cavitation. Finally, the correlation between the parameters of the heat treatment – the structure – behavior at cavitational erosion compared to those of the untreated thermal alloy was determined.

Effect of Homogenization Process on Microstructure and Mechanical Properties of 4047 Aluminum Alloy

In this study, the homogenization heat‐treatment process and microstructural evolution of 4047 aluminum alloy are investigated. In the results, it is revealed that the homogenization process induces partial dissolution of metastable phases and modification of the fine needle‐shaped eutectic Si. Within the 4047 aluminum alloy, the fine needle‐shaped eutectic Si undergoes granulation, involving two stages: crystal dissolution and granulation of broken crystals. After optimal homogenization heat treatment, the eutectic Si phase transformed from a fine needle‐shaped structure to small, regular spherical structures, reducing stress concentration and improving the interfacial bonding capability and internal structure of the alloy matrix. This significantly reduces the likelihood of microcrack formation within the alloy and effectively hinders crack propagation, enhancing the alloy's mechanical properties.

Influence of preparation processes with or without long-time homogenization heat treatment on performance of Nd–Fe–B HDDR products

We investigated the influence of hydrogenation-disproportionation-desorption-recombination (HDDR) preparation processes, with or without long-time homogenization heat treatment, on the microstructure and hard magnetic properties of Nd12.7B6.5Co2.1Cr0.1Al0.5Nb0.3Ga0.5Fe77.3 powders/bonded magnets. Hard magnetic properties such as remanence (Br = 1.01 T), coercivity (Hcj = 949.39 kA/m), and maximum magnetic energy product (BH)max = 181.54 kJ/m3 were achieved for HDDR bonded magnets with homogenization heat treatment. In contrast, magnets prepared without homogenization heat treatment exhibited Br = 0.65 T, Hcj = 854.69 kA/m, and (BH)max = 66.98 kJ/m3. The notable decrease in remanence for magnets prepared without homogenization treatment is attributed to the presence of α–Fe in the parent alloy, which inhibits the hydrogenation-disproportionation process and consequently affects the orientation of the crystallographic texture. Furthermore, we fabricated bonded quadrupole magnetic rings using HDDR powder prepared with homogenization heat treatment. The study also explored the relationship between disproportionation temperature and surface magnetic field intensity for these quadrupole magnetic rings.

Influence of Homogenization and Quench-Aging Heat Treatments on Dry Wear Behavior of Al-40Zn-3Cu Alloy

The influence of homogenization and quench-aging treatments on the dry sliding friction and wear behavior of Al-40Zn-3Cu bearing alloy was experimentally studied. These treatments removed dendritic structure of the alloy and caused the formation of zinc-rich precipitates distributed homogenously in the matrix of the alloy. It was observed that quench-aging treatment carried out at temperatures of 100 °C and 150 °C significantly improved both hardness and strength of the alloy as compared to homogenization treatment. However, aging at 200 °C lowered these values of the alloy but increased its elongation. Dry sliding wear test results displayed that homogenization and quench-aging treatments increased the wear performance of the alloy. However, it is found that the quench-aging treatment created more powerful effect for improving wear performance of the alloy than homogenization. Quench-aging treatment at 100 °C for 300 min resulted in a decrease in the lowest specific wear rate of the alloy by causing the highest increases in its hardness (from 119 HB to 178 HB), yield strength (from 288 MPa to 383 MPa) and tensile strength (from 319 MPa to 407 MPa) due to the age hardening mechanism. It was observed that the worn surfaces of the alloy samples were composed of adhered and smeared material and delaminated areas. This observation suggested that adhesion and delamination were the operative wear mechanisms of the alloy. The results were explained and discussed in terms of microstructural features, mechanical properties, and wear mechanisms of Al-40Zn-3Cu alloy.

CALPHAD-guided design and experimental study on a novel Al-Ti-Nb alloy

We have used a CALPHAD-guided design methodology to develop a novel lightweight Al-Ti-Nb alloy with nearly 50 vol% of in-situ formed trialuminide reinforcement. After compositional optimization, we selected Al87.5Ti6.25Nb6.25 (at%) as the experimental alloy composition and subjected it to a 24-hour homogenization heat-treatment at 475°C for attainment of equilibrium, guided by DSC and CALPHAD-derived melting point data. Phase and microstructure analysis revealed a microstructure with approximately 50 vol% of a FCC Al-rich matrix and 50 vol% of trialuminide phases for strengthening. The experimental onset melting point of the Al-rich matrix was determined to be 647°C, which significantly surpasses Al-Si based high-temperature alloys (577 ℃), showcasing the potential of this alloy as a high-temperature structural material. Nanoindentation tests demonstrated exceptional mechanical properties. The alloy was found to have a microhardness of 3350 MPa, which not only outperformed 7075 Al alloy, A390 Al-Si alloy, and commercially pure Ti but also exceeds the levels of Ti-6Al-4V alloy at nearly 28% lower density. This study's significance lies in its integration of CALPHAD predictions and meticulous microstructural investigation, offering an effective approach for the design and characterization of novel Al-based alloys.

Effect of the Fe/Mn Ratio on the Microstructural Evolution of the AA6063 Alloy with Homogenization Heat Treatment Interruption

The casting structure of the AA6063 alloy contains intermetallic particles of β-Al5FeSi, which can result in the fragility of the cast pieces. However, with heat treatment, the β phase transforms from a needle or plate form into an intermetallic phase known as α, which resembles Chinese-script in its morphology. To analyze the effect of the ratio of Fe/Mn with different ratios of 0.5, 0.75, and 1, a heat treatment process is used with intermittent interruptions. The alloy is subjected to a temperature of 575 °C for 12 h to determine the microstructural evolution of the β-Al6FeMn and α-Al15(FeMn)3Si2 phases. This study used scanning electron microscopy to conduct point analyses and elemental mappings of the intermetallics found in the casting and heat treatment samples. Additionally, X-ray diffraction was employed to determine the stoichiometry of the present phases. The results indicated that the cast structure contains β-Al6FeMn and α-Al15(FeMn)3Si2 phases and that the β-Al6FeMn phase transforms into the α-Al15(FeMn)3Si2 phase upon completion of the heat treatment process. By using specific Fe/Mn ratios, the formation of the needle-shaped Al5FeSi phase in the casting structure of the alloy can be inhibited, leading to the precipitation of phases such as β-Al6FeMn and α-Al15(FeMn)3Si2 instead.

A low-cost Mg–Al–Mn–Zn alloy for automotive road wheel applications

In this study, a new Mg–Al–Mn–Zn alloy (AMZ211) was designed, aided by thermodynamic modeling, for applications in automotive road wheels using forging and flow-forming processes. The AMZ211 alloy was cast and forged in an industrial scale to obtain a forged blank to evaluate its tensile properties and hot formability under high-strain-rates (simulating flow-forming conditions). Multiple characterization techniques, including optical, scanning electron and scanning transmission electron microscopy as well as electron backscatter diffraction, were applied to investigate the microstructural evolution during the processing route. As expected from the alloy design, nano-sized Mn-containing dispersoids formed in a homogeneous manner during homogenization heat treatment, contributing to the formation of refined dynamically recrystallized (DRXed) grains in as-forged microstructure. The as-forged AMZ211 alloy showed better hot formability than as-forged AZ80 Mg alloy under high-strain-rate condition as well as a comparable strength property in relative to the benchmark and more expensive Mg–Zn–Zr alloys. The lower ductility of as-forged AMZ211 alloy may be due to the high twinning tendency of coarse unDRXed domains which were formed as a result of the original coarse-grained microstructure from solidification. The present study provides a low-cost Mg alloy for high-volume automotive road wheel applications.

Correction: Effects of Homogenization Heat Treatment on Microstructure, Mechanical and Corrosion Properties of Transient Liquid Phase (TLP)-Bonded Inconel 617/AISI 310 Stainless Steel

Correction: Effects of Homogenization Heat Treatment on Microstructure, Mechanical and Corrosion Properties of Transient Liquid Phase (TLP)-Bonded Inconel 617/AISI 310 Stainless Steel

Influence of Morphological Change of Eutectic Si during Homogenization Heat Treatment on the Microstructure and Strength at Elevated Temperatures in Wrought Al–Si–Cu–Mg–Ni Alloy

Influence of Morphological Change of Eutectic Si during Homogenization Heat Treatment on the Microstructure and Strength at Elevated Temperatures in Wrought Al–Si–Cu–Mg–Ni Alloy