Heat-treated Specimens Research Articles

Effect of hard anodizing and T6 heat treatment on the dry sliding wear behavior of AlSi10Mg fabricated by direct metal laser sintering

This paper investigated the influence of hard anodizing (HA) and T6 heat treatment (HT) on the dry sliding wear characteristics of the AlSi10Mg alloy fabricated via direct metal laser sintering (DMLS). Hard anodizing was conducted in a sulfuric acid bath at 40 V for 1000 s, while the heat treatment comprised solutionizing at 530 °C for 1 h, followed by artificial aging at 150 °C for 8 h. The tribological tests were performed using the ball-on-flat mode in a high-frequency linear reciprocating tribometer under applied loads of 5 N and 10 N. The results show that the microhardness of the HA specimen increased by 1.2 times compared to the as-built condition, while the hardness of the as-built specimen declined by 44% after T6 treatment. The hard-anodized samples exhibited a 30% enhancement in wear resistance attributable to the development of a persistent and uniform distribution of oxide layers leading to pore closure and reduced surface roughness. In contrast, the T6 heat treatment resulted in an increased pore size, roughness, and grain coarsening, as validated by SEM and XRD results. Adhesion, abrasion, and delamination were the predominant wear mechanisms in the as-built specimens under all loads. In contrast, the HA specimens featured abrasion and oxidative wear mechanisms under all loads, and the HT specimens exhibited delamination wear accompanied by crack propagation. The findings underscore the essential importance of post-treatment selection to improve the wear resistance and durability of DMLS-manufactured AlSi10Mg components for industrial use.

The Customized Heat Treatment for Enhancing the High-Temperature Durability of Laser-Directed Energy Deposition-Repaired Single-Crystal Superalloys.

The high-temperature durability performance plays a crucial role in the applications of single-crystal (SX) superalloys repaired by laser-directed energy deposition (L-DED). A specialized heat treatment process for L-DED-repaired SX superalloys was developed in this study. The effect of the newly customized heat treatment on the microstructure and high-temperature mechanical properties of DD32 SX superalloy repaired by L-DED was investigated. Results indicate that the repaired area of the newly customized heat treatment specimen still maintained a SX structure, the average size of the γ' phase was 236 nm, and the volume fraction was 69%. Obviously recrystallized grains were formed in the repair area of the standard heat treatment specimens, and carbide precipitated along the grain boundary. The size of the γ' phase was about 535 nm. The high-temperature durable life of the newly custom heat treatment specimen was about 19.09 h at 1000 °C/280 MPa, the fracture mode was microporous aggregation fracture, and the fracture location was in the repair area. The durable life of the standard heat treatment specimen was about 8.70 h, the fracture mode was cleavage fracture, and the fracture location was in the matrix area. The crack source of both specimens was interdendrite carbide.

Effect of heat treatment on the microstructure, mechanical properties and tribological behavior of Ti-45Nb alloy fabricated by laser powder bed fusion

To avoid stress-shielding effects between biomedical implants and human bones, low modulus heat-treated Ti-45Nb specimens fabricated by laser powder bed fusion (LPBF) after annealing heat treatment were studied in this study. The microstructure and mechanical properties of the specimens revealed that (i) the as-built specimen consisted mainly of the β-TiNb phase, and heat treatment did not affect the phase species, demonstrating the thermal stability of the LPBFed Ti-45Nb alloy. (ii) After heat treatment, all the specimens exhibited excellent yield strengths (over 1100 MPa), and low Young's moduli (approximately 80 GPa). (iii) The specimens exhibited excellent wear resistance with the main wear modes of abrasive and adhesive wear and low COF (0.353-0.394) under a load of 20 N.

Heat treatments-induced wear resistance of Inconel 718 superalloy fabricated via Laser based Powder Bed Fusion

Laser based Powder Bed Fusion (LPBF) stands out among Additive Manufacturing (AM) techniques for its ability to fabricate intricate geometries with high precision. However, LPBF produced parts, particularly Inconel 718 (IN718) superalloys, demand further exploration in microstructural and mechanical properties aspect. This study explores the effect of heat treatments on LPBF fabricated Inconel 718. Three distinct heat treatments involving diverse solutionizing temperatures and ageing steps were applied to the LPBFed IN718 alloy. As-printed samples showed columnar dendritic microstructure. The heat treatments led to precipitation of strengthening γ′′ and γ′ phases. A substantial increase in microhardness was observed after heat treatments. Wear tests revealed as-printed specimens suffered higher wear loss (∼889 μm) and coefficient of friction (COF) (∼0.627) attributed to Laves phase and low hardness of the matrix. However, heat-treated specimens exhibited substantially lower wear loss (∼217 μm) and COF (∼0.342), with HT2 condition demonstrating superior wear resistance attributed to a homogeneous microstructure.

Effect of Printing Parameters and Heat Treatments on Microstructure Development of LPBF Manufactured Inconel 718 Alloy

Abstract Processing parameters of the laser powder bed fusion (LPBF) technique strongly govern achieved performances and manufacturing defects of printed alloys. In this work, it was aimed to study the effects of LPBF printing parameters and subsequent heat treatments on resulted microstructure characteristics and tensile properties of Inconel 718 alloy. Inconel samples were fabricated using three different energy densities. Then, microstructure features such as Lave phase, primary dendrite arm spacing, and internal residual stresses as microstrains of both as-built and heat-treated specimens were determined. It was found that in the range of used energy densities, alterations of phase fractions and average sizes of the Laves phase were insignificant. Decreased energy density led to microstructures with smaller primary dendrite arm spacing and thus principally contributed to enhanced yield and tensile strengths of as-printed samples, whereas increased porosity greatly deteriorated elongation. Moreover, their flow stress curves could be significantly increased by direct aging; however, typical cellular and columnar substructures occurring during the LPBF printing remained. Homogenization treatment could entirely eliminate such substructures and otherwise caused different formations of delta phase when it was performed prior to a delta process.

Very high cycle fatigue properties of short glass fiber reinforced polyetheretherketone (PEEK)

The fatigue properties of 14 wt-% short glass fiber reinforced polyetheretherketone (PEEK–GF14) have been investigated in the high and very high cycle fatigue (VHCF) regime. Experiments were performed at a load ratio of –1 with servohydraulic and electrodynamic equipment at cycling frequency 10–20 Hz, and with ultrasonic equipment at 19 kHz. A new specimen geometry has been developed that allows ultrasonic tests up to high stress amplitudes. The same specimen shape was used in both testing series to exclude size effects, which enabled to focus on the influence of cycling frequency and testing technique. Ultrasonic fatigue testing with intermittent loading served to avoid heating of specimens. The S-N curves measured at 10–20 Hz and 19 kHz show a similar slope exponent (i.e., 10 % deviation). Mean S-N curve determined with ultrasonic equipment is shifted to slightly lower stress amplitudes, which may be attributed to statistical scatter. PEEK–GF14 does not show a fatigue limit and failures still occurred above 109 cycles. The VHCF strength of PEEK-GF14 is approximately two times higher compared with unreinforced PEEK. Fractographic investigations revealed fiber fracture and, less frequently, fiber pull-out.

Post-fire flexural buckling and resistances of square recycled aggregate concrete-filled stainless steel tube (RACFSST) columns

The flexural buckling behaviour and residual resistances of square recycled aggregate concrete-filled stainless steel tube (RACFSST) columns after exposure to fire are studied in this paper, based on experiments and numerical modelling. Twelve column specimens, fabricated from concretes with three recycled coarse aggregate replacement ratios (0%, 35% and 70%), were tested after exposure to the ISO 834 standard fire for 0 min (i.e. at ambient temperature), 15 min, 30 min and 45 min. The experimental investigation included heating of specimens, cylinder tests as well as post-fire initial global geometric imperfection measurements, tensile coupon tests and pin-ended column tests. The test setups, procedures and results were fully reported and the ductility indices, lateral deflection distributions and longitudinal strains were discussed and analysed. A numerical investigation was afterwards carried out, where the test results were used to validate thermal and mechanical finite element models; upon validation, parametric studies were conducted to expand the test data bank over a wider range of cross-section dimensions and member lengths. On the basis of the test and numerical data, the relevant design rules for square natural aggregate concrete-filled carbon steel tube columns at ambient temperature, as set out in the European code, Australian/New Zealand standard and American specification, were assessed, using post-fire material properties, for their applicability to square RACFSST columns after exposure to fire. It was found from the assessment results that the three design codes resulted in overall accurate and consistent post-fire flexural buckling resistance predictions but some were unsafe.

Research on the Mechanism of Oxygen-Induced Embrittlement Fracturing in Industrial Electrolytic Nickel.

In this study, severe cracking occurred during an investigation of the direct hot rolling of industrial electrolytic nickel plates. To determine the cause of hot-rolling cracking, the microstructure phase composition was analyzed through the utilization of various techniques, including optical microscopy, scanning electron microscopy, electron backscattering diffraction, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and electron probe micro-analysis. The comparative microstructural analysis took place between specimens heat treated in atmospheric and vacuum environments. The characterization and analysis of the hot-rolled plates considered the crack microstructure and fracture morphology. It was shown that holes appeared along the large angular grain boundaries after annealing at 1100 °C for 8 h. Possible reason: In a high-temperature environment, the decomposition of residual additives in the electrolytic nickel releases oxidizing gases, which oxidizes the grain boundaries. The reaction with carbon diffused into the grain boundaries and produced carbon monoxide gas, which induced holes and severely reduced the grain boundary plasticity. The heat treatment time did not need to be very long for severe grain boundary degradation to occur. After severe cavitation, the electrolytic nickel was severely cracked at grain boundaries cracks due to a shear force, and brittle fractures occurred along grains with very low plasticity.

Corrosion of aluminium alloy AA2024-Τ3 specimens subjected to different artificial ageing heat treatments

The effect of artificial-ageing on corrosion behaviour of aluminium alloy (AA)2024-T3 was investigated. The natural ageing which takes place during the aircraft's lifespan was simulated with isothermal heat-treatments at 190 °C. Electrochemical impedance spectroscopy measurements were performed in different heat-treated specimens to examine the prevailing corrosion mechanisms. Additionally, pre-corroded tensile specimens from different heat-treatment conditions were mechanically tested to assess the corrosion-induced degradation. Different forms of corrosion were revealed in the investigated ageing tempers; intense localized attack was noticed in the initial (T3) and under-aged (UA) tempers. UA condition exhibited the highest susceptibility to corrosion propagation followed by T3, according to the charge transfer resistance RCT and degradation rate of tensile elongation at fracture Af ( ≈ 0.118) and ( ≈ 0.103), respectively. Corrosion-induced degradation rates for the peak-aged (PA) and over-aged (OA) tempers ( ≈ 0.042 and 0.054, respectively) were almost one third of UA, attributed to volume fraction and size of the precipitated second-phase particles.

Investigations on tribological behavior under lubricated condition of post heat treated additively manufactured SS316L parts

PurposeThe purpose of this paper is to investigate the friction and wear mechanisms in lubricated sliding conditions of additively manufactured SS316L parts. The different viscous oils 5W30, 15W40, 20W50 and SAE140 are used. These investigations provide a theoretical basis for the high performance of printed and postheattreated SS316L.Design/methodology/approachTribological tests were carried out on selective laser melting-made SS316L printed specimens and heat-treated specimens. The parameters in 15 min of test duration are 20 N of load, 200 rpm, 8 mm of pin diameter, 25 mm length, 80 mm of track diameter and EN31 counter disc body. This work presented the phenomena of lubrication regimes and their characterization, as identified by the Stribeck curve, and these regimes affect the tribological properties of additively manufactured SS316L under the influence of industrial viscous lubricants. The results are observed using Scanning electron microscope (SEM), X-ray diffraction (XRD) and wear tests.FindingsThe observations indicate that additively manufactured SS316L shows a reduced coefficient of friction (COF) and specific wear rate (SWR). This is credited to the utilization of different viscous lubricants.Originality/valueThis exclusive research demonstrates how various viscous lubricants affect the COF and SWR of printed and post-heat-treated SS316L parts. Lambda (λ), lubricant film thickness (h0), surface roughness and wear mechanisms are studied and reported.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2024-0110/

Rotating bending fatigue behavior of high-pressure diecast AlSi10MgMn alloy based on T5 heat treatment parameters

Abstract The study investigates fatigue failure, a common phenomenon in machine elements subjected to cyclic stresses. The analysis emphasizes that the actual stress experienced by materials often falls below their tensile and yield strengths due to repetitive variable stresses, leading to fatigue damage. Fatigue life is measured by the number of cycles endured before failure. This paper focuses on the aluminum alloy of AlSi10MgMn, extensively used in manufacturing due to its strength, low density, and corrosion resistance. Experimental procedures encompassed tensile testing, microstructural examination, SEM analysis, and fatigue testing. Tensile tests provided initial stress values for fatigue testing. Microstructure analyses verified that heat-treated samples exhibited precipitates. SEM analysis disclosed microstructural characteristics, while fracture surface examinations demonstrated higher fatigue resistance in heat-treated specimens. Hardness measurements were conducted, with heat-treated samples showing higher values. Theoretical calculations based on stress and cycle numbers were compared to experimental fatigue results. The derived equations aligned well with the tests. Ultimately, the study underlines the importance of heat treatment on material behavior and fatigue resistance, shedding light on alloy performance and durability enhancement.

Insight into elongation and strength enhancement of heat-treated LPBF Ni-based superalloy 718 using in-situ SEM-EBSD

This study presents a detailed investigation into the deformation behaviour and the factors affecting the strength and ductility of laser powder bed fusion (LPBF) Ni-based superalloy 718 (Inconel 718) in both as-printed and heat-treated conditions using in-situ SEM + EBSD. The results show that following post-deposition high homogenization temperatures, the columnar grain structure of the as-printed Inconel 718 alloy successfully transformed to a nearly uniform grain size and the subsequent aging processes facilitated the precipitation of strengthening phases (γ′, γ''). The specimen subjected to heat treatment (HT1) exhibited higher strength but lower ductility, while the as-printed specimen shows higher tensile elongation due to high initial dislocation density. In contrast, the heat-treated (HT2) specimen presented a more optimal combination of strength and ductility. The underlying mechanism for the enhanced tensile properties in the HT2 specimen was nearly homogeneous deformation trend across the grains and ultrafine precipitation of hardening phases. In addition, the twin boundaries were stable in the early deformation stages and maintained their orientation. Multiple slip systems were activated at the high-deformation stage, resulting in a high proportion of geometric necessary dislocations. Further, the interaction of deformation-induced dislocation with twin boundaries transformed them into general boundaries such as high and low-angle grain boundaries, ultimately increasing ductility. On contrary, in the HT1 specimen, the deformation inhomogeneity in grains enabled the strain localization at grain boundaries, which ultimately caused the early formation of cracks.

Temperature Effect on Deformation Mechanisms and Mechanical Properties of Welded High-Mn Steels for Cryogenic Applications.

High-manganese steel (high-Mn) is valuable for its excellent mechanical properties in cryogenic environments, making it essential to understand its deformation behavior at extremely low temperatures. The deformation behavior of high-Mn steels at extremely low temperatures depends on the stacking fault energy (SFE) that can lead to the formation of deformation twins or transform to ε-martensite or α'-martensite as the temperature decreases. In this study, submerged arc welding (SAW) was applied to fabricate thick pipes for cryogenic industry applications, but it may cause problems such as an uneven distribution of manganese (Mn) and a large weldment. To address these issues, post-weld heat treatment (PWHT) is performed to achieve a homogeneous microstructure, enhance mechanical properties, and reduce residual stress. It was found that the difference in Mn content between the dendrite and interdendritic regions was reduced after PWHT, and the SFE was calculated. At cryogenic temperatures, the SFE decreased below 20 mJ/m2, indicating the martensitic transformation region. Furthermore, an examination of the deformation behavior of welded high-Mn steels was conducted. This study revealed that the tensile deformed, as-welded specimens exhibited ε and α'-martensite transformations at cryogenic temperatures. However, the heat-treated specimens did not undergo α'-martensite transformations. Moreover, regardless of whether the specimens were subjected to Charpy impact deformation before or after heat treatment, ε and α'-martensite transformations did not occur.

Effect of heat treatment on the shear fracture and acoustic emission properties of granite with thermal storage potential: A laboratory-scale test

The exploitation of geothermal resources enhances the energy structure but poses challenges related to thermal–mechanical issues. This study utilizes short core in compression (SCC) specimens of granite to investigate thermo-mechanical properties. We examined the effects of heat treatment temperature on physical properties, shear fracture toughness, as well as acoustic emission (AE) characteristics. Fracture surface morphology and microstructure of the heat-treated SCC specimens were also analyzed using 3D laser scanning and scanning electron microscopy. Results indicate that both mass loss and P-wave velocity decrease with increasing heating-treated temperature, and similar trends are observed in mechanical properties. Specifically, fracture energy and shear fracture toughness decline by 51.48 % and 61.27 %, respectively, as temperature rises from 25 °C to 750 °C. The b-value and proportion of shear cracks initially increase before falling, with an inflection point at 300 °C, linked to thermal-induced microstructural deterioration. Fractal dimension (D) and joint roughness coefficient (JRC) show significant increases with higher heat treatment temperatures. Microstructural degradation, including dehydration and thermal-induced microcracking, drives the reduction in shear properties of heat-treated granites. Overall, our findings offer valuable insights into determining various methods of heat storage reconstruction with great application potential.

Effects of Heat Treatment on the Chemical Composition and Microstructure of Cupressus funebris Endl. Wood

The effects of heat treatment on Cupressus funebris Endl. wood were examined under different combinations of temperature, time, and pressure. The chemical composition, crystallinity, and microstructure of heat-treated wood flour and specimens were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Vacuum heat treatment led to changes in the functional groups and microstructure of C. funebris wood, and the relative lignin content decreased with increasing treatment temperature, which was significant at lower negative pressures. Cellulose crystallinity showed a change rule of first increasing and then decreasing throughout the heat treatment range, and the relative crystallinity ranged from 102.46% to 116.39%. The cellulose treated at 120 °C for 5 h at 0.02 MPa had the highest crystallinity of 44.65%. These results indicate that although heat treatment can improve cellulose crystallinity, very high temperatures can lead to decreased crystallinity. The morphology and structure of the cell wall remained stable throughout the heat treatment range; however, at elevated temperatures, slight deformation occurred, along with rupture of the intercellular layer.

Effect of heat treatment on electrochemical behavior of biocompatible Ti–Ta–Nb–Zr alloys prepared by selective laser melting

In this paper, cytotoxicity-free Ti-10Ta-2 Nb-2Zr titanium alloy was prepared by selective laser melting additive manufacturing. The effect of solution and annealing heat treatment on the structure and microhardness were investigated. Electrochemical performance in Ringer’s solution at 37℃ was evaluated. This electrochemical evaluation was performed through the open circuit potential variation as the immersed time, potentiodynamic polarization curves, and electrochemical impedance spectroscopy tests. The results show that main phase composition of as-built and heat-treated specimens was the α/α′ phase. The specimen annealed at 500℃ presented a small amount of β phase. The solutionized and annealed specimens had basket-weave microstructure with distributed micro-scaled α/α′ lamellas. The microhardness of as-built specimens was 400.48 ±12.31 HV. After solution and water quenching, the microhardness dramatically increased to 533.85 ±24.67 HV. The microhardness slightly decreased to 495.46 ±4.85 and 488.8 ±13.84 HV after annealing at 300 ℃ and 500 ℃, respectively. Compared with the as-built specimen, the solutionized and annealed specimens had much lower corrosion current density and higher corrosion resistance.

Heat treatments effects on Wear performance of Laser based Powder Bed Fusion fabricated Inconel 718 alloy

Among the AM processes Laser based Powder Bed Fusion (LPBF) technique offers precise and complex geometric fabrication. However, the microstructural and mechanical properties obtained from LPBF process requires further investigation, especially for IN718 superalloys. In this study, various heat treatments were applied to LPBFed Inconel 718 specimens to examine their effects on microstructure, microhardness and wear behavior. Three different heat treatments, each involving varied solutionizing and ageing steps were incorporated. As-printed specimens exhibited distinct fish scale structures with columnar dendrites. Heat treatments effectively dissolved the Laves phase and precipitated strengthening phases like γ′′ and γ′. Microhardness increased significantly after heat treatments, correlating with the formation of strengthening precipitates. Friction and wear tests showed as-printed specimens exhibited higher wear loss (922 ± 13 μm) and coefficient of friction (COF) (0.511 ± 0.07) due to the presence of Laves phase and softer matrix. Heat-treated specimens demonstrated significantly reduced wear loss (262 ± 5 μm) and COF (0.368 ± 0.01), with HT2 showing the best wear resistance attributed to a homogeneous microstructure. SEM analysis of worn surfaces confirmed abrasive and adhesive wear mechanisms in as-printed specimens, while heat-treated specimens exhibited reduced wear with smoother surfaces.

Enhancing the tribological characteristics of the biocompatible Ti-6Al-4 V alloy via heat treatment: An experimental analysis

The tribological behaviour of the Ti-6Al-4 V biocompatible alloy fabricated using laser powder bed fusion (LPBF) was experimentally investigated for prosthesis implants. Annealing heat treatment was executed to improve its tribological performance. The microstructure and microhardness characterization were performed using scanning electron microscope (SEM) and Vickers microhardness. The wear test was processed using a SS304 spherical ball in simulated body fluid (SBF) at body temperature. The ball on a flat tribometer was used to determine wear rate, depth, width, and friction coefficient at 15 N. The results revealed that a needle-like martensite α' structure was noticed on the as-deposited sample. Microstructural characterization significantly affects wear morphologies. The heat-treated specimen showed a more desirable wear performance than the as fabricated.

Improving the fatigue life of laser powder bed fusion Scalmalloy® by friction stir processing

A major concern about parts produced by laser powder bed fusion (L-PBF) are intrinsic defects or porosities that are difficult to overcome by simply optimizing the process parameters. As these defects and porosities play a crucial role in the mechanical behaviour, especially in fatigue, additive manufactured parts are often subjected to thermo-mechanical post-treatments. To this end, this work proves Friction Stir Processing (FSP) to be an effective post-treatment to drastically reduce the porosity level. FSP leads to an improvement of 60 % of the technical fatigue strength and by two orders of magnitude of the fatigue life of L-PBF Scalmalloy® specimens. The fatigue performances obtained on FSPed and heat-treated specimens are equivalent or even better than the best fatigue life reported in the literature, whatever their L-PBF conditions and post-treatments, while avoiding Hot Isostatic Pressing. However, FSP reduces the beneficial effect of the conventional strengthening heat-treatment applied to L-PBF Scalmalloy®, lowering the high tensile strength for which the alloy is normally reputed. Advanced characterisation by X-ray microtomography and Transmission Electron Microscopy allows us to reach a better understanding of the involved phenomena: drastic reduction of the biggest defects and heterogeneous nucleation of Sc- and Zr-rich precipitates on grain boundaries and dislocations.

Low Temperature Pyrolysis and Exfoliation of Waste Printed Circuit Boards: Recovery of High Purity Copper Foils

Although several techniques have been developed to extract copper from waste printed circuit boards (PCBs), there remain several challenges regarding energy consumption, local area contamination and environmental damage. A novel technique has been developed for extracting copper foils from waste PCBs based on low temperature pyrolysis followed by exfoliation to overcome these issues. The standard pretreatment steps of removing electronic components from PCBs and mechanical processing/size-reduction/powdering, etc., were minimized in this study. Several unsorted ‘as received’ PCBs were heat treated in the temperature range 750–850 °C for 5–20 min. in an argon atmosphere. Brittle dark chars and other residues on the heat-treated specimens were scrapped off to separate copper foils and other residuals. Most of the electronic components mounted on PCBs had dropped off during the heat treatment. Good-quality copper foils were recovered in all cases; the purity of copper was in excess of 85 wt.%. Key impurities present were Pb, Sn and Zn with typical concentrations less than 4 wt.%. Key features of the technique include minimizing energy intensive pre-treatment processes and waste handling, low pyrolysis temperatures and short heating times. This energy-efficient approach has the potential to enhance resource recovery while reducing the loss of materials, local area contamination and pollution near e-waste processing facilities.