Columnar Crystals Research Articles

Effect of preheating temperature on the microscopic structure and mechanical performance of pulsed laser welding in sheet AZ31 alloy

To achieve high quality welding of an AZ31 magnesium alloy sheet, butt experiments are conducted using an Nd:YAG pulsed laser welder to weld the AZ31 magnesium alloy (1 mm). The influence of preheating temperature on the microscopic structure and mechanical performance of AZ31 magnesium alloy pulsed laser welding is studied. Experimental results show that with the rising of preheating temperature, the grain size of an equiaxed crystal in the weld center and columnar crystal at the fusion boundary (FB) first decreases and then increases and reaches the minimum values of 18.89 ± 0.45 and 32.09 ± 1.52 μm, respectively, when preheated at 200 °C. The maximum force and tensile strength increase first and decrease and reach the maximum of 2.32 kN and 193.3 MPa, respectively, when the preheating temperature is 300 °C. Above all, the welds with excellent mechanical performance can be obtained at the preheating temperature of 300 °C.

Double pulsed current adopted in local dry underwater WAAM to simultaneously enhanced strength and ductility of 308 L multi-layer component

The double pulsed current waveform modulation was applied to address the severe challenges of greatly declined strength and ductility caused by continuous heat accumulation and water cooling in local dry underwater wire arc additive manufacturing (LDU-WAAM) process. The microstructures and mechanical performance of 308 L stainless steel multi-layer components prepared by LDU-WAAM using single pulsed waveform (SPW) and double pulsed waveform (DPW) were comprehensively investigated in this work. The results demonstrate that the microstructures of LDU-WAAM parts were both composed of abundant columnar crystals and few equiaxed crystals. Extremely directional columnar crystals dominated in each deposited layer centre prepared by SPW, while the weakened growth tendency of columnar crystal and uniform microstructure were achieved by DPW. DPW exhibited outstanding stirring action in LDU-WAAM process, which was conducive to the refined grain, improved liquidity of deposited metal, increased ferrite content, dislocation density, and austenite deformed twinning content compared with the SPW multi-layer component. Hence, the average microhardness, ultimate tensile strength, and elongation of DPW deposited layers were improved to 204.7 HV, 659.2 MPa, and 24.9 %, respectively, which enhanced by 10.1 %, 12.5 %, and 37.5 % than that of SPW sample. The research results provide a new technique optimization method to simultaneous enhance the strength and ductility of LDU-WAAM process and promote the landing application of LDU-WAAM in underwater on-site repair.

Effects of beam oscillation on porosity and microstructure of laser welded TC11 titanium alloy

Oscillating beam was used for laser welding of TC11 titanium alloys. The porosity, microstructure, and mechanical properties of welds with different parameters were studied. It was found that increasing the oscillation frequency could effectively suppress porosity. When the oscillation amplitude was less than or equal to 1 mm, the laser power was about 3 kW, and the welding speed was less than 15 mm/s, porosity could be effectively suppressed. Both oscillation frequency and amplitude could increase the number of α′-phase. The oscillation frequency promoted the cross distribution of α′-phase and α″-phase in the columnar crystal. The oscillation amplitude promotes the uniform distribution of α′-phase in the columnar crystal. Increasing the oscillation frequency and the oscillation amplitude was beneficial to increase the tensile strength. In the case of low defect rates, the tensile strength of the weld could reach more than 90% of the base metal, and the maximum elongation was 7.5%.

Evolutions of microstructure and mechanical property of 308L stainless steel repaired by the local dry underwater wire arc additive manufacturing

Local dry underwater wire arc additive manufacturing process (LDU-WAAM) was innovatively proposed to repair the damaged large underwater structures. A thorough investigation was performed to explore the microstructure and mechanical properties of 308L stainless steel multi-layer components prepared by LDU-WAAM technique. The results demonstrate that the microstructure of all components was composed of a significant amount of austenite and a minor amount of ferrite. Subjected to the repeated action of local arc heating and rapid water cooling, the multi-layer components were deposited into a stratified structure, each layer was mainly composed plenty of directional columnar crystals, and the adjacent layers were separated by a small number of equiaxed crystals. With the increase of deposited layer counts, the heat transfer paths from deposited metal to the substrate were gradually lengthened, which increased average grain size, LAGBs proportion, dislocation density, and austenite deformed twinning content of the multi-layer sample, also decreased its ferrite content. Hence, the microstructure of LDU-WAAM multi-layer component varied significantly from the bottom to the top, which led to the deteriorated mechanical properties along the building direction. In the 3-layer component, the ultimate tensile strengths of the first, second, and third layers were 554 MPa, 532 MPa, and 519 MPa, respectively. And the elongations of that were 25.3%, 23.2%, and 19.5%, respectively. The research results verify the feasibility of local dry underwater wire arc additive manufacturing process and provide a new process method for underwater on-site repair.

Powder bed fusion repair of titanium with surface damage: Molecular dynamics study on microstructure and mechanical properties

Additive manufacturing has been emerging as a highly efficient method that minimizes the consumption of virgin materials and energy to rapidly repair the damaged parts and potentially recover the original performance. Here, the microstructures and mechanical properties of polycrystalline titanium (Ti) with surface damage after powder bed fusion (PBF) repair and post-polishing treatment are investigated by molecular dynamics simulations. It is found that during PBF repair of the surface damage by melting Ti nanoparticles, grain boundaries (GBs) in polycrystalline Ti are more susceptible to damage from temperature elevation than the grain interiors. During the solidification process, grains grow in the form of columnar crystals. After PBF repair and post-polishing treatment, the yield strength of damaged samples is recovered to 96.8% of that of perfect ones. This restoration can be attributed to the increased capacity of carrying dislocations due to that the GB directional growth generates dislocation walls after PBF repair. More importantly, the flow stress exceeds that of the perfect sample due to the increase in stacking faults and the appearance of twins after PBF repair, which enhance the resistance of dislocation motion. The fatigue performance of the damaged samples processed by combinatorial PBF repair and post-polishing treatment is found to surpass that of perfect samples. This is attributed to that the elimination of rough surface and the reduction of intragranular dislocations avoid dislocation entanglement that otherwise results in strain concentration, and also prevent the premature occurrence of twins and the rapid increase in stacking faults during the cyclic loading, thus retarding the nucleation of intergranular cracks. Our molecular dynamics simulation results could help shed light on the atomic mechanism of microstructure evolution during PBF repair and mechanical performance after PBF repair.

Effect of Sputtering Bias Voltage on the Microstructure and Lead-Bismuth Eutectic Corrosion Resistance of the FeCrAlY Coating

FeCrAlY coatings deposited on the outer surface of the cladding tube by the magnetron sputtering with varying bias voltages (0 V to −500 V) were corroded at 550°C to 600°C in oxygen-saturated and oxygen-poor lead-bismuth eutectic for 500 h to 1,000 h. The increased bias voltage led to the Al content decreased and the Y content increased. The coating changed from columnar crystals to equiaxed crystals with increased bias voltage. The decreased bias voltage makes an improved corrosion resistance. The fundamental process governing the evolution of microstructure and corrosion resistance in the FeCrAlY coatings was discussed.

Approaching theoretical strength in aluminum alloys via directional heterogeneous nanostructured design

Strengthening a material to its theoretical limit is the unremitting pursuit in the field of materials science and engineering. However, it remains extremely difficult for polycrystalline alloys to reach the theoretical limit using conventional strengthening methods. Here, we propose a directional heterogeneous nanostructured strategy (DHNS) to develop super-strong metallic materials. Based on the microstructural strategy, an aluminum-titanium alloy was developed with a yield strength up to ∼3.9 GPa approaching the theoretical limit (G/τY∼22) and a record-breaking specific strength (∼1219 KNm/kg) among metals and alloys. Microstructural characterizations showed that the DHNS alloy mainly consists of directional nanoscale columnar fcc-Al crystals surrounded by nanosized stripe amorphous phases. The columnar crystals are shown to be in hard orientation and defect free, behaving crystalline whisker-like properties. The synergistic effect of hard-orientation nano-colunmar crystals and strong nanoscale amorphous phases renders the initiation of plastic flow difficult, eventually leading to the ultrahigh yield strength of the alloy. The DHNS strategy provides a facile and effective method for developing strong metallic materials especially for fcc-type alloys where slip systems are easy to be activated.

Grain Morphology and Mechanical Properties Tailoring of Inconel 625 Alloy Fabricated by Laser Powder Bed Fusion

The controlling strategies of grain morphology and mechanical properties of Inconel 625 alloy by laser powder bed fusion are investigated, and beyond that, the effects of phase composition, grain morphology, and crystallographic texture on mechanical properties are also studied. The phase evolution is insensitive to the scanning strategies, and all of the samples are composed of γ‐Ni phase. The (001) texture orientation tends to increase with the scanning rotation angle, and the sample IV fabricated by scanning strategies of 90° shows the highest (001) texture. Different grain morphologies can be tailored by controlling the direction of heat flow between continuous layers via changing scanning strategies. The proportion of large elongated columnar crystals gradually decreases, while the proportion of the equiaxed grains gradually increases as the scanning strategies change from 0°→90→67°→45°. The rotation angle increases from 0° to 45°, and the ultimate tensile strength and yield strength increase from 1267 ± 12 to 1304 ± 5 MPa and 760 ± 10 to 801 ± 5 MPa, respectively, which is attributed to the different stress states presented in the columnar crystals and the equiaxed crystals.

High-pressure minerals and new lunar mineral changesite-(Y) in Chang’e-5 regolith

Forty-five years after the Apollo and Luna missions, China’s Chang’e-5 (CE-5) mission collected ∼1.73 kg of new lunar materials from one of the youngest basalt units on the Moon. The CE-5 lunar samples provide opportunities to address some key scientific questions related to the Moon, including the discovery of high-pressure silica polymorphs (seifertite and stishovite) and a new lunar mineral, changesite-(Y). Seifertite was found to be coexist with stishovite in a silica fragment from CE-5 lunar regolith. This is the first confirmed seifertite in returned lunar samples. Seifertite has two space group symmetries (Pnc2 and Pbcn) and formed from an α-cristobalite-like phase during “cold” compression during a shock event. The aftershock heating process changes some seifertite to stishovite. Thus, this silica fragment records different stages of an impact process, and the peak shock pressure is estimated to be ∼11 to 40 GPa, which is much lower than the pressure condition for coexistence of seifertite and stishovite on the phase diagram. Changesite-(Y), with ideal formula (Ca8Y)□Fe2+(PO4)7 (where □ denotes a vacancy) is the first new lunar mineral to be discovered in CE-5 regolith samples. This newly identified phosphate mineral is in the form of columnar crystals and was found in CE-5 basalt fragments. It contains high concentrations of Y and rare earth elements (REE), reaching up to ∼14 wt. % (Y,REE)2O3. The occurrence of changesite-(Y) marks the late-stage fractional crystallization processes of CE-5 basalts combined with silicate liquid immiscibility. These new findings demonstrate the significance of studies on high-pressure minerals in lunar materials and the special nature of lunar magmatic evolution.

Influence of energy density on the microstructure and property regulation of additive manufactured pure nickel

In this work, laser powder bed fusion (LPBF) technology was used to fabricate pure nickel components, and the densification behavior and microstructure of pure nickel with different energy densities were investigated. The results indicate that for LPBF-fabricated pure nickel components, the relative density reaches a peak of 98.76% at an energy density of 101 J/mm3. With the increase of energy density, a large number of pores appear inside the grains, and the grains grow epitaxially along the building direction within multiple molten pools, pores gradually disappear after undergoing remelting at the edges of the melting tracks. Among these, competitive inward growth of columnar crystals may be the main cause of dislocations and new grain generation. The grains are primarily distributed along the Ni (111) or Ni (110) orientations, and with the increase of energy density, the grains with these two orientations increase. The surface energy follows the sequence of Ni (220) > Ni (200) > Ni (111). Due to the stacking of the <101> oriented main layer and the <001> oriented sub-layer in the building direction, the sample with higher energy density exhibits a strong Ni {110} texture, accompanied by increased tensile properties.

Simulation and Experimental Study on the Effect of Superheat on Solidification Microstructure Evolution of Billet in Continuous Casting.

The control of the solidification structure of a casting billet is directly correlated with the quality of steel. Variations in superheat can influence the transition from columnar crystals to equiaxed crystals during the solidification process, subsequently impacting the final solidification structure of the billet. In this study, a model of microstructure evolution during billet solidification was established by combining simulation and experiment, and the dendrite growth microstructure evolution during billet solidification under different superheat was studied. The results show that when the superheat is 60 K, the complete solidification time of the casting billet from the end of the 50 mm section is 252 s, when the superheat is 40 K, the complete solidification time of the casting billet is 250 s, and when the superheat is 20 K, the complete solidification time of the casting billet is 245 s. When the superheat is 20 K, the proportion of the equiaxed crystal region is higher-the highest value is 53.35%-and the average grain radius is 0.84556 mm. The proportion of the equiaxed crystal region decreases with the increase of superheat. When the superheat is 60 K, the proportion of the equiaxed crystal region is the lowest-the lowest value is 46.27%-and the average grain radius is 1.07653 mm. Proper reduction of superheat can obviously reduce the size of equiaxed crystal, expand the area of equiaxed crystal and improve the quality of casting billet.

Microstructure and Mechanical Properties of Al-Li Alloys with Different Li Contents Prepared by Selective Laser Melting.

Research on the development of new lightweight Al-Li alloys using a selective laser melting process has great potential for industrial applications. This paper reports on the development of novel aluminum-lithium alloys using selective laser melting technology. Al-Cu-Li-Mg-Ag-Sc-Zr pre-alloyed powders with lithium contents of 1 wt.%, 2 wt.% and 3 wt.%, respectively, were prepared by inert gas atomization. After SLM process optimization, the microstructure and mechanical properties of the as-printed specimens were investigated. The densifications of the three newly developed alloys were 99.51%, 98.96% and 92.01%, respectively. They all had good formability, with the lithium loss rate at about 15%. The as-printed alloy with 1% Li content presented good comprehensive properties, with a yield strength of 413 ± 16 MPa, an ultimate tensile strength of 461 ± 12 MPa, and an elongation of 14 ± 1%. The three alloys exhibited a layered molten pool stacking morphology and had a typical heterostructure. The columnar crystals and equiaxed fine grains were alternately arranged, and most of the precipitated phases were enriched at the grain boundaries. The change in Li content mainly affected the precipitation of the Cu-containing phase. When the Li content was 1 wt.%, the following occured: θ phase, T1 phase and TB phase. When Li increased to 2 wt.%, T1 and T2 phases precipitated together. When Li reaches 3 wt.%, δ' phase precipitated with T2 phase. This study provides useful guidance for the future SLM forming of new crack-free and high-strength Al-Li alloys.

Stability analysis and porosity inhibition mechanism of oscillating laser-arc hybrid welding process for medium-thick plate TC4 titanium alloy

The influence of oscillating laser frequency and oscillation diameter on the stability and porosity of laser-arc hybrid welding of titanium alloys were investigated. The microstructure and basic mechanical properties of oscillating laser-arc hybrid welded joints were revealed. The results show that the oscillating laser significantly improved the macroscopic morphology of the joints, reducing the porosity from 5.48 % to 0.12 %. In the conventional laser-arc hybrid welding process, the number of keyhole surface closures was more and the time of droplet transition was longer, resulting in poor process stability. When the frequency was 150 Hz and the diameter was 1.5 mm at oscillating laser conditions, the number of keyhole closures within 200 ms was significantly reduced to 5 times compared to the conventional laser-arc hybrid welding (23 times). The droplet transition was stable, which resulted in a more stable hybrid welding process. In addition, after one oscillation cycle, the forward distance of the laser was relatively short, which can reopen the smaller pores generated in the previous cycle, leading to a significant reduction in porosity. When the frequency and diameter of oscillation decreased, the fluctuation for keyhole morphology was greater and the droplet transition was instability, resulting in an increase in porosity; When the oscillation increased, the fluctuation of the keyhole outer diameter was larger and the penetration depth decreased, which was not conducive to the welding of medium-thick plates. In the oscillating laser-arc hybrid welding process, columnar crystals in the middle of the molten pool grew towards the surface, reducing the segregation of impurities in the weld center. As a result, the elongation percentage of the joints was improved by 36.58 % compared to the conventional laser joints.

Improving the corrosion and wear resistance of CoCrNiSi0.3 Medium-Entropy Alloy by magnetron sputtered (CrN/Cr)x multilayer films

In this study, a medium entropy alloy (MEA) system consisting of Co, Cr, and Ni was selected to incorporate Si, resulting in the creation of CoCrNiSi0.3 MEA. The surface was coated with (CrN/Cr)x multilayer films to improve wear and corrosion resistance. The hardness, wear, corrosion, and nanoindentation tests were used to analyze the characteristics of CrN/Cr multilayer films and their protective performance. Low grazing angle X-ray diffraction (GIXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), water contact angle analyzer, and transmission electron microscopy (TEM) were utilized to investigate the composition and structure of (CrN/Cr)x multilayer films. The intermediate Cr layer inhibits the columnar growth of the CrN layers and is progressively refined as the number of CrN/Cr bilayers increases. The Cr layer exhibits superior toughness in the multilayer structure and effectively hinders crack propagation. Therefore, the (CrN/Cr)3 multilayer film has the most outstanding anti-wear performance. The wear rates under 2 N and 4 N loads are 3.331 × 10−6 mm3•m−1•N−1 and 1.124 × 10−5 mm3•m−1•N−1, respectively. The growth of columnar crystals is suppressed and a more compact multilayer film is formed, resulting in a reduction in the defect density and an increase in the water contact angle, which retards the ingress of corrosive liquid and improves corrosion resistance. The corrosion current density of the (CrN/Cr)3 multilayer film is 0.73 μA•cm−2, while the corrosion polarization impedance is 962.35 Ω•cm2.

Effect of heat treatment on the microstructure and mechanical properties of laser melting deposition copper-containing antibacterial stainless steel

Heat treatment was conducted on copper-containing antibacterial stainless steel prepared by laser melting deposition (LMD) under three different strategies (Planar, serpentine, chessboard), and its effect on microstructure and mechanical properties was studied.. Solid solution treatment at 1050 °C-15 min and aging treatment at 800 °C-6 h/12 h were applied to achieve antibacterial properties in the steel. The results show that the LMD-based stainless steel specimens have an interlocking fish scale shape, with cellular crystals in the melt pool and columnar crystals with different growth directions at the boundaries. After heat treatment, the results show that the fish scale melt pool boundary gradually becomes shallower, and the grain transitions to equiaxed crystal. Moreover, the fracture surface after stretching exhibits uniform equiaxed dimples, indicating ductile fracture. LMDed specimens to have high strength but poor toughness. After solid solution treatment, the strength decreased by about 24 %, and the toughness increased by 25.98 %. After the aging treatment, the second phase strengthening effect of the copper-rich stage made the material stronger and higher. In short, after heat treatment, component segregation is eliminated, the structure is more uniform, and the overall performance of the material is improved.

Effect of WC on microstructure, molten pool and properties of Ni based coatings by multi-layer laser cladding

Ni45 powder and tungsten carbide (WC) particles were added to laser cladding coatings by to improve the wear resistance and impact resistance of mechanical components. The microstructure and elements of the coatings were assessed using SEM and TEM. A high-speed camera was used to analyse the morphology of the molten pool during the cladding process. The wear resistance and impact resistance of the coatings were tested by a wear and impact testing machine. The reaction of WC in the molten pool releases a large amount of thermal energy, which gives the molten pool a faster flow rate. The flow rate increases rapidly at WC dosages of ≤10 wt% and more slowly at dosages >10 wt%. Flow in the molten pool causes the WC to break the columnar crystals in the pool, which form a large number of coarse cellular crystals. WC causes the coatings to precipitate more rich Cr hard phase and intermetallic compounds, which increases their abrasion resistance and impact performance. The wear rate of the coating containing 12 wt% WC was 91.59% lower than that of the Ni45 coating. However, the impact resistance was decreased by the stress concentration and brittleness of the WC.

Novel diphenylacrylonitrile-decorated cyclotriveratrylene columnar liquid crystals with high fluorescence

ABSTRACT Although some cyclotriveratrylene (CTV) liquid crystals had been reported, the CTV liquid crystal with high fluorescence in mesophase was not presented up to now. By introducing diphenylacrylonitrile units on CTV skeleton, two CTV derivatives with AIE units (7a and 7b) were prepared for the first time. Their structures and crown conformations were characterised by 1H NMR, 13C NMR, MALDI-MS spectra and elemental analysis. Samples 7a and 7b exhibited the reversible liquid crystalline behaviours with hexagonal columnar mesophase supported by the DSC, POM and XRD analysis. The studies on photophysical properties of samples 7a and 7b suggested the high fluorescence in solid state and mesophase. The absolute fluorescence quantum yield of 7b in mesophase was as high as 0.45. This work not only reported the first CTV liquid crystals with high fluorescence in aggregated state but also provided a good strategy for constructing the novel CTV liquid crystals with excellent fluorescence.

Microstructures and mechanical properties of nano-TiC/Ti-refined Al[sbnd]Mg alloys prepared by wire arc additive manufacturing

In the current study, an AlMg alloy refined with a nano-TiC/Ti grain refiner was successfully printed by cold metal transition wire arc additive manufacturing (CMT-WAAM). The effects of the nano-TiC/Ti grain refiner on the microstructure and mechanical properties of the CMT-WAAM-prepared AlMg alloy were studied. The results indicated that the nano-TiC/Ti grain refiner has a significant refining effect on AlMg alloy and refined the coarse columnar crystals into uniform fine equiaxed crystals. The average grain size of the CMT-WAAM AlMg alloy refined with the 0.6 wt% nano-TiC/Ti grain refiner decreased from 53.06 μm to 25.32 μm (yz plane), and the average grain size in the xy plane decreased from 52.00 μm to 25.80 μm. The excellent grain refinement effect of the nano-TiC/Ti grain refiner was attributed to the presence of TiC particles at the grain, which acted as heterogeneous nucleation sites and improved the nucleation rate. Moreover, TiC particles located at the grain boundary inhibited the growth of the grain boundary. The mechanical properties, i.e., the tensile and yield strength, were improved by 20–25%, and there was an increase in the microhardness (~9.5%) of the CMT-WAAM AlMg alloy refined with the 0.6 wt% nano-TiC/Ti grain refiner.

Substantial grain refinement of Al-Mn-Si alloys mediated by collaborative effect of Al-5Ti-1B refiner and sub-rapid solidification

The mechanical properties of as-cast metallic materials depend strongly on the size and shape of grains, which are critical microstructural parameters dictated by the interplay of nucleation and growth of crystalline solids during solidification. In our experiments, the microstructure transition from coarse columnar crystals into fine equiaxed crystals for dilute Al-Mn-Si alloys was achieved by using sub-rapid solidification with the addition of Al-5Ti-1B grain refiner. The average grain size of Al alloy was reduced from a millimeter size to 73 µm. Through temperature gradient calculation, we found that the acquisition of fine equiaxed crystals could be attributed to the existence of a high number density of TiB2, acting as effective nucleation sites with an increase in total undercooling. Furthermore, the curvature supercooling, constitutional undercooling, thermal undercooling, and kinetic undercooling during sub-rapid solidification were quantitatively determined for given solidification rates. Our results showed that constitutional undercooling, rather than thermal undercooling, was primarily responsible for the formation of fine equiaxed grains, with the assistance of Al-5Ti-1B grain refiner. This work provides a new insight into the grain refining mechanism under sub-rapid solidification.

Difference of properties after heat treatment between GH4169 and GH3536 alloys fabricated by direct energy deposition

In this study, thin-walled parts of GH4169 and GH3536 superalloys were prepared using the direct energy deposition (DED) method, respectively. The results revealed that solution aging treatment was effective in eliminating the boundary of the molten pool and refining the grain structure to some extent. Subsequently, the Laves phase redissolved in the γ matrix, releasing Nb element. This was followed by the formation of γ′, γ″, and δ phases, which effectively improved the yield strength and tensile strength of the GH4169 alloy after high temperature heat treatment. In the case of the GH3536 alloy, heat treatment caused a change in microstructure from columnar crystals to larger equiaxed crystals. Additionally, chain carbides precipitated at the grain boundaries, which increased the elongation after fracture but decreased the yield strength and tensile strength to some extent. Following solid solution aging treatment, the ultimate tensile strength of GH4169 deposited parts exhibited a 27.7% increase in the deposition direction and a 15.6% increase in the laser scanning direction. Conversely, the tensile strength of GH3536 showed minimal variations, but the elongation in both directions experienced notable improvements, rising by 22% and 20.7%, respectively. Solution aging treatment further eliminated the mechanical anisotropy of the two superalloys due to the inhomogeneity of microstructure and grains, as well as the existence of molten pool boundaries and grain boundary segregation. Furthermore, the microstructure and mechanical properties of GH3536 alloy were found to be better than those of GH4169 alloy, both before and after aging.