Effect Of Post Heat Treatment Research Articles

Substructure boundary's enhancing strain hardening ability in additively manufactured 0.75 at%C doping NiCoCr medium entropy alloy

In this study, the effect of post heat treatment on microstructural evolution and tensile properties of 0.75% of carbon doped NiCoCr MEA alloy manufactured by laser powder bed fusion (LPBF) was investigated. The post heat treatment of LPBF-built 0.75C MEA alloy was selected and carried out at 700 °C for 1hr, respectively. The microstructural observation in heat-treated 0.75C MEA HT sample shows a lower stacking fault energy (SFE) with wider stacking fault width (SFW) compared to as-built condition. In-situ nano-sized precipitates are formed along the sub-boundaries of the as₋built 0.75C MEA and 0.75C MEA HT samples which are estimated as 1.25 % and 2.45 %, respectively. After post heat treatment process, the size and ratio of nano-sized precipitates enhanced and identified as Cr-rich M23C6 carbide. Subsequently, the yield and tensile strengths increase from 823.2 MPa to 872.7 MPa and 1.05 GPa–1.15 GPa for 0.75C MEA and 0.75C MEA HT conditions, respectively which is attributed to the prevailing solid solution strengthening and precipitation strengthening. The deformation twins in as−built specimen are transformed to twin bundle once the local strain increases from 5% to 20%. The 0.75C MEA HT deformed specimen exhibits high dislocation accumulation with retained stable substructure in local strain 20% area due to the pinning effect of nano-sized precipitates which stabilizes and strengthens the substructure boundary i.e., Dynamic Hall-Petch mechanism. These results provide a new perception for achieving better strength performance by post heat treatment process for NiCoCr-based medium entropy alloys (MEA) alloy.

Effects of post-heat treatments on the microstructure and mechanical properties of Ti-6Al-4V alloy fabricated by selective laser melting

In this study, post-heat treatments were applied to Ti-6Al-4V (TC4) alloy fabricated by selective laser melting (SLM) to investigate the effects of annealing temperature (750 to 950 °C in 50 °C intervals) on the alloy's microstructure, residual stress and mechanical properties. The initial microstructure of as-SLMed TC4 alloy was dominated by needle-like α' martensite with a high density of dislocations and minor β phase, resulting in high strength (1190 MPa) but limited ductility (2.2% elongation). Annealing led to the transformation of α' martensite into α phase, with the β phase content remaining relatively stable. Increasing the annealing temperature caused the acicular martensite to evolve into bundles of coarse α laths, forming a basket-weave microstructure. Annealing at 750 °C for 2 h reduced the yield strength to 1040 MPa and improved elongation to 8.3%. Interestingly, both the strength and ductility decreased with further increases in annealing temperature. This unusual phenomenon was rarely mentioned in current literature and was considered to be associated with the abnormal variations in the Schmid factor of (0001)[11-20] slip system and the reduction of mobile dislocations within the coarsened α martensite. Additionally, annealing combined with air cooling effectively alleviated residual tensile stresses in the SLM-formed TC4 alloy.

High-temperature oxidation behavior of a novel γ′-strengthened superalloy manufactured by laser-beam powder bed fusion: Effect of post-heat treatment

This study systematically researched the high-temperature oxidation behavior of a γ′-strengthened alloy based on Haynes 230 prepared by laser-beam powder bed fusion (PBF-LB). The results indicate that the experimental alloy showed a higher oxidation resistance than Haynes 230 at 1000 °C. The oxidation products mainly consisted of the outmost MnCr2O4-TiO2 layer, intermediate Cr2O3 layer and inner TiO2 layer. Branched Al2O3 oxides were formed in the interior oxidation zone. Post-heat treatment can increase oxidation resistance by reducing the oxidation rates from 0.0152 mg2cm−4h−1 to 0.0126 mg2cm−4h−1. The decrease in dislocation density and the precipitation of ordered γ' phases can slow down the short-circuit diffusion and lattice diffusion rate of oxygen, and are the main reasons for this improvement. Furthermore, the γ' phase precipitation and dislocation density reduction can provide more sites for Cr2O3 nucleation and reduce the Cr supply required for grain growth. As a result, the Cr2O3 grains on the heat-treated sample surface were smaller.

Effects of post heat treatment on key T-phase evolution and the matching mechanism of enhanced strength-toughness, wear resistance and corrosion resistance in Al-Mg-Zn-(Cu-Er-Zr) alloy by laser powder bed fusion

Al-Mg-Zn-(Cu-Er-Zr) system alloy is a novel alloy designed by materials genetic method for laser additive manufacturing of lightweight brake discs and the T-phase (T-AlMgZnCuZrEr) in this alloy is the most important microstructure for enhancing performance matching of the alloy. Scientifically regulating the T-phase evolution through innovative preparation processes to improve the matching of strength-toughness, wear resistance, and corrosion resistance in this novel alloy is the fundamental work for preparing high-performance lightweight high-speed train brake disc parts using laser additive manufacturing. In this work, laser powder bed fusion and post heat treatments were employed to prepare Al-Mg-Zn-(Cu-Er-Zr) alloy samples with the superior matching of strength-toughness, wear resistance and corrosion resistance, and the key T-phase evolution and performance enhancement mechanisms of the samples were studied. The results indicate that post heat treatments significantly influenced the quantity, size, and structure of the T-phase in the cladded sample, which significantly enhanced the strength-toughness, wear resistance and corrosion resistance matching of the alloy. It is found that under the optimized aging treatment at 200 °C/6 h, due to the evolution of T-phase area fraction and cell-like structure inside the T-phase, the strength-toughness, wear resistance and corrosion resistance were improved by 30 %, 28 %, 1.4 %, respectively. The precipitation and concave dissolution mechanisms of the T-phase during post heat treatment have been finely revealed, and a three-performance matching relationship model has been successfully constructed based on the strength-toughness matching equation. A new laser powder bed fusion followed by the aging process to manufacture an Al-Mg-Zn-(Cu-Er-Zr) alloy sample with the superior matching of strength-toughness, corrosion resistance, and wear resistance has been obtained, which provides a valuable reference for laser additive manufacturing high-performance lightweight aluminum alloy brake disc parts.

Effects of Post-Heat Treatment and Carbide Precipitates on Strength-Ductility Balance of GH3536 Superalloy Prepared by Selective Laser Melting

Effects of Post-Heat Treatment and Carbide Precipitates on Strength-Ductility Balance of GH3536 Superalloy Prepared by Selective Laser Melting

Dynamic Response of Ti-6Al-2Zr-1Mo-1V Alloy Manufactured by Laser Powder-Bed Fusion.

Titanium parts fabricated by additive manufacturing, i.e., laser or electron beam-powder bed fusion (L- or EB-PBF), usually exhibit columnar grain structures along the build direction, resulting in both microstructural and mechanical anisotropy. Post-heat treatments are usually used to reduce or eliminate such anisotropy. In this work, Ti-6Al-2Zr-1Mo-1V (TA15) alloy samples were fabricated by L-PBF to investigate the effect of post-heat treatment and load direction on the dynamic response of the samples. Post-heat treatments included single-step annealing at 800 °C (HT) and a hot isotropic press (HIP). The as-built and heat-treated samples were dynamically compressed using a split Hopkinson pressure bar at a strain rate of 3000 s-1 along the horizontal and vertical directions paralleled to the load direction. The microstructural observation revealed that the as-built TA15 sample exhibited columnar grains with fine martensite inside. The HT sample exhibited a fine lamellar structure, whereas the HIP sample exhibited a coarse lamellar structure. The dynamic compression results showed that post-heat treatment at 800 °C led to reduced flow stress but enhanced uniform plastic strain and damage absorption work. However, the HIP samples exhibited both higher stress, uniform plastic strain, and damage absorption work owing to the microstructure coarsening. Additionally, the load direction had a subtle influence on the flow stress, indicating the negligible anisotropy of flow stress in the samples. However, there was more significant anisotropy of the uniform plastic strain and damage absorption. The samples had a higher load-bearing capacity when dynamically compressed perpendicular to the build direction.

Selective laser melting of a novel Al-Si-Fe-Mn-Ni alloy with superior mechanical properties at both room and elevated temperatures: Influence of processing parameters and heat treatment

In this study, a novel heat-resistant Al-Si-Fe-Mn-Ni alloy suitable for selective laser melting technique was developed. By optimizing the process parameters, as-built alloy with few defects and superior mechanical properties was manufactured at a laser power of 350 W and a scanning speed of 1300 mm/s, with horizontal and vertical ultimate tensile strengths of 589 and 529 MPa, respectively. Conventional annealing, solid solution and T6 treatments were conducted to investigate the effect of post heat treatments on the microstructure and mechanical properties. Owing to the low diffusion capacity of Fe, Mn and Ni elements, the alloys show excellent high-temperature stability. The initial eutectic structure is retained after annealing, with few changes in the morphology of the precipitated phases. During solution treatment, the AlSi eutectic breaks up to form diffusely distributed Si particles, and Fe, Mn-rich intermetallic compounds as well as AlFeNi phases gradually precipitate out, which further occurs in T6 state. Due to its high-temperature resistance, the alloy developed in this study exhibits better high-temperature mechanical properties than conventional commercial AlSi10Mg alloys, showing higher strength in high-temperature tensile experiments from 150 °C to 300 °C.

Effect of post-heat treatment on the UV transmittance, hydrophobicity, and tensile properties of PVA/Uncaria gambir extract blend films

The physical and mechanical properties of biopolymers can be improved by heating technologies. In this research, we improved the properties of Polyvinyl alcohol (PVA)/Uncaria gambir extract (UGE) blend films by post-heating method. After post-heating, the blend film exhibited higher resistance to UV light and improved contact angle performance, while water vapor permeability and moisture absorption decreased. The tensile strength and toughness of the PVA/UGE blend film with a post-heating duration of 40 min were 68.8 MPa and 57.7 MPa, respectively, an increase of 131 % and 127 %, compared to films without post-heating. This facile and cost-effective fabrication method, with environmentally friendly properties, can be applied to biodegradable PVA/UGE blend films to achieve desired properties for optical devices or food packaging materials.

Self-assembled titanium-based macrostructures with hierarchical (macro-, micro-, and nano) porosities: A fundamental study

This study details the novel self-assembly of sodium titanate converted Ti-based microspheres into hierarchical porous 3D constructs, with macro-, micro-, and nanoporosity, for the first time. Ti6Al4V microspheres were suspended into 5 M NaOH (60 °C/24 h) solutions, with extensive variations in microsphere:solution ratios to modify microsphere interaction and initiate self-assembly through proximity merging of titanate surface dendritic growth. The formed structures, which either produced 1) unbonded, sodium titanate-converted microspheres; 2) flat (non-macroporous) scaffolds; or 3) open, hierarchically porous scaffolds, were then assessed in terms of their formation mechanism, chemical composition, porosity, as well as the effect of post-heat treatments on compressive mechanical properties. It was found that specific microsphere:solution ratios tended to form certain structures (<⅓ powder, 0.5 to 3 porous, >3 flat non-macroporous, >8 powder) due to a combination of microsphere freedom of movement, H2 gas bubble formation, and exposed surface reactivity. This promising discovery highlights the potential for lower temperature, simplistic production of 3D constructs with modifiable chemical properties due to the ion-exchange potential of titanate structures, with clear applications in a wide-range of fields, from medical materials to catalysts.

Effects of post heat treatment on the microstructure and mechanical properties of selective laser melted AlSi10Mg alloys

The effects of direct aging (DA), annealing (AN), solid solution (ST), annealing + aging (AA) and solution + aging (SA) on the microstructure and mechanical properties of AlSi10Mg alloys fabricated by selective laser melting were studied. The results showed that direct aging can completely preserve the network Si structure of the as-built (AB) alloy, and the ultimate tensile strength of horizontal and vertical samples were both increased from 486 MPa to 487 MPa–502 MPa and 515 MPa, respectively. Annealing can lead to the disintegration and breaking up of eutectic Si networks, with the coarsening of grains and the deduction in dislocation density, the strength of the alloy was significantly reduced and the plasticity was improved. Annealed + aged alloys had the highest plasticity, with both transverse and longitudinal elongation exceeding 20 %. After solution treatment, the eutectic grid in the alloy completely collapsed and Si particles grew into coarse blocks. The transverse ultimate tensile strength was barely 256 MPa, which increased to 281 MPa after aging. The direct aging process adopted in this study further enhances the strength of the as-built AlSi10Mg alloy, providing a certain reference significance for optimizing the post heat treatment of AlSi10Mg.

Effect of Post-heat Treatment on Microstructure and Mechanical Properties of Laser Cladded High Co-Ni Secondary Hardening Steel Coating

The effect of post-heat treatment on the microstructure and microhardness of laser cladded high Co-Ni secondary hardening steel coating was investigated. The microstructures were analyzed using a SEM equipped with an EDS, and the microhardness was measured with a Vickers indenter. Decomposition of the retained austenite in the coating occurred during the post-heat treatment. As the temperature increased from 200 °C to 600 °C, the quantity of the retained austenite at the boundaries decreased significantly, while that of the needle-shaped M3C cementite and M2C carbides increased. The M2C carbides evidently coarsened when the temperature was higher than 500 °C. The microhardness of high Co-Ni steel coating increased as the temperature of post-heat treatment increased from 200 °C to 400 °C because the fine-scale M2C carbides were coherent with the matrix and increased distinctly in this temperature range. It decreased sharply when the temperature further increased from 500 °C to 600 °C due to both the incoherency of the coarsened M2C carbides and the recovery of dislocations in the carbon-supersaturated matrix.

Post-heat treatment effect on dielectric and optical properties of magnesium-based spinel

Post-heat treatment effect on dielectric and optical properties of magnesium-based spinel

Characterization of sol-gel derived NiO thin films: Effect of post-heat treatment

Characterization of sol-gel derived NiO thin films: Effect of post-heat treatment

Optimization of Printing Process Variables and the Effect of Post-Heat Treatments on the Mechanical Properties of Extruded Polylactic Acid-Aluminum Composites.

Polymer extrusions are employed in the fabrication of crucial parts for automotive, aerospace, and other mechanical applications. The use of fillers and microfibers is contributing to the advancement of material extrusion polymers. In order to enhance their mechanical characteristics, printed materials undergo a post-heating process utilizing microwaves. Specimens were fabricated using polylactic acid filaments containing 2 wt% aluminum. Two sets of specimens were fabricated and subjected to testing in order to evaluate the features of extruded specimens and specimens that underwent post-heating. In terms of mechanical performance, specimens subjected to post-heating exhibited superior results compared to specimens merely subjected to extrusion. The tensile, flexural, and Shore D hardness properties of the specimens exhibited improvements of 5.07, 6.16, and 1.32%, respectively, after being subjected to heating. Furthermore, the wear rate decreased by 13.58 percent. The results of the regression analysis indicate that the print angle and the air gap exhibit the greatest influence on the observed responses. The validation test outcomes exhibit a high level of concordance with the predicted findings. The mechanical and surface properties of components extruded with filler-added material are enhanced by subsequent heating.

The effect of post heat treatment and TiO2 addition on tribological and electrochemical performances of thermally sprayed alumina

ABSTRACT The heat treatment of alumina ceramics is a fundamental process for controlling the physical, mechanical and thermal properties of these components during industrial operations. The problem statement in this case is about the effects of TiO2 addition and post heat-treatment on the expansion behaviour of alumina coating. For that alumina (Al-99) and alumina-titania coatings 5% wt. TiO2 (AT-5) and 15% wt. TiO2 (AT-15) were formed onto E335 substrate steel via the flame spraying technique. The samples were heat-treated (1000°C for 2 h in Air) and their wear and electrochemical behaviour was compared with the as-sprayed samples. The X-ray diffraction (XRD) patterns reveal a change in the phase composition of the heat-treated coatings compared to the as-sprayed coatings, as alpha alumina matrix but with different ratio. The heat-treated coatings exhibit higher values to as-sprayed coating. At the same time, the addition of TiO2 present hardness twice than pure alumina coating (Al-99). The tribological properties show that the deposits after heat treatment have low wear values compared to the as-sprayed coatings, the lowest specific wear rate was obtained for the heat-treated AT-5 composite coatings. The heat treatment had a positive effect on the corrosion resistance.

Effect of post-heat treatment on the microstructure, mechanical, and corrosion properties of laser powder bed fused Al–Zn–Mg–Cu–Si–Zr–Er alloys

Three different post-heat treatments, including direct aging (DA), solution heat treatment + precipitate hardening (T6), and retrogression and re-ageing (RRA), were carried out on a Si–Zr–Er modified Al–Zn–Mg–Cu alloy, which is manufactured by laser powder bed fusion (LPBF). The results show that direct aging maintains the cellular structure of the as-printed (AP) alloy, while T6 and RRA promoted the damage and decomposition of the cellular structure. The size of the primary Al3(Er,Zr) phase increased after heat treatment, and secondary Al3(Er,Zr) phases were uniformly distributed in the matrix with a size of 5–20 nm. The Mg2Si phase in the DA alloy was a long strip pattern, but uniformly distributed in the T6 and RRA alloy. The ultimate tensile strength of the AP, DA, T6, and RRA alloys reached 468, 474, 389, and 354 MPa, respectively. The size, shape, and distribution of the Al3(Er,Zr) and Mg2Si phases have a significant impact on their corrosion resistance, with the latter having a stronger effect. To sum up, the strength of the DA alloy is increased, but its corrosion performance is decreased with heat treatment. On the other hand, the strength of the T6 and RRA alloys is somewhat sacrificed, but their plasticity and corrosion resistance are significantly enhanced.

Post-heat treatment of laser powder bed fusion fabricated Al–La–Mg–Mn alloy: On intermetallic morphology control and strength-ductility balance

In this study, a newly developed Al–La–Mg–Mn alloy was subjected to solution heat treatment for the first time. During the solution heat treatment at 500 ℃, the continuous network Al11La3 intermetallics were transformed into a discontinuous granular form. Ultrafine intermetallics (∼0.20 µm) were achieved via multi-point spheroidization with the aid of endogenous nanoprecipitates. Of note, the intragranular intermetallics were inert to coarsening, while the intergranular intermetallics grew gradually to ∼0.58 µm within 6 h. Compared to the as-printed alloy (UTS ∼588 MPa, Elongation ∼6.4%), the solution-treated alloy at 500 ℃ for 1 h (UTS ∼477 MPa, Elongation ∼14.3%) demonstrated a remarkable improvement in ductility, with a 123% increase, despite a modest decrease of 19% in strength, thereby balancing the strength-ductility. The limited decline in strength is primarily attributed to the high-content solute Mg atoms and thermally stable intragranular intermetallics. Interestingly, the mechanical properties were independent of the holding times at 500 ℃, despite the coarsening of intergranular intermetallics. This is mainly due to the optimization of intermetallics’ scale distribution, which tailors and equalizes the stress distribution between the grain boundary and interior, as well as between the melt pool boundary and interior during deformation. These findings provide the first insight into the effect of post-heat treatment on the intermetallic evolution and mechanical properties of LPBF Al–(La, Ce) alloys.

Friction deposition additive manufacturing of alloy 718: Effect of post-heat treatment on microstructures and mechanical properties

Friction deposition additive manufacturing of alloy 718: Effect of post-heat treatment on microstructures and mechanical properties

Effect of post-heat treatment with super β transus temperature on the damping behaviour of LPBF-processed Ti6Al4V thin rotor blade

This article investigates the damping behaviour of laser powder bed fusion-processed Ti6Al4V thin plate samples and thin rotor blades. The effect of microstructural changes owing to the post heat treatments (PHTs – 850 °C, 950 °C and 1050 °C) on damping behaviour was assessed. The microstructural characterisation was performed using optical microscopy, X-ray diffraction and scanning electron microscope techniques. The impact hammer test was performed on thin plate samples and rotor blades to characterise damping behaviour. The microstructure of the thin plate samples subjected to PHT conditions varied in grain structure and morphology compared to the as-printed ones. Further, PHT at a higher temperature (i.e. 1050 °C) induces a higher amount of β phase than the other PHT temperatures. The PHT performed at 1050 °C exhibited α- Widmanstätten microstructure consisting of elongated β and a small amount of α. Moreover, the frequency response function plots revealed broader peaks for thin plate samples and the rotor blade than others. The PHT was favourable in enhancing the α lath thickness and β volume fraction, increasing the damping ratio. The results showed that PHT performed at 1050 °C improves the overall damping of ∼348% and ∼140% of rotor blade and thin plate samples, respectively. The amplitude decay for the rotor blade subjected to PHT at 1050 °C was ∼66% shorter than the as-printed one due to high β phase content relieving the energy resulting in a high damping ratio.

Effects of post-heat treatment on anisotropic mechanical properties of laser additively manufactured IN718

In this presented work, the effects of different heat treatments on the anisotropic mechanical properties of Inconel 718 (IN718) fabricated by laser powder bed fusion (LPBF) and laser directed energy deposition (LDED) were comparatively investigated. Samples prepared in build direction (BD) and transverse direction (TD) for tensile and creep tests were heat-treated with Solution + double aging (SA) and Homogenization + solution + double aging (HSA) procedures, separately. Experimental results indicate that both SA-treated LPBF-IN718 and LDED-IN718 show strong anisotropy in tensile and creep properties. TD samples have higher tensile strength and relatively better creep performance. After HSA treatment, LPBF-IN718 samples still show strong anisotropic tensile and creep properties. In contrast, anisotropy in mechanical properties of LDED-IN718 samples is mitigated significantly. The columnar grains in as-built LDED-IN718 recrystallized after HSA treatment, resulting in similar tensile and creep properties in both directions. The difference in residual stresses of LPBF-IN718 and LDED-IN718 is the main reason that causes the totally different conditions after HSA treatment. This work can provide a deeper understanding of the difference in anisotropic mechanical properties of LPBF-IN718 and LDED-IN718, which may guide the design of proper heat treatment of laser additively manufactured nickel-based superalloy potentially.