Solution Treatment Temperature Research Articles

Designing the heat treatment process for Mg-10Gd-4Y-xZn-0.6Zr (wt.%) alloy: A study on the transformation of microstructure and properties

Heat treatment of Mg10Gd-4Y-xZn-0.6Zr (x = 0, 1, 2 wt%) alloys has been optimized based on thermodynamic calculations and experiments. The phase transformations during the heat treatment and their effect on the mechanical properties of the alloys were discussed. Using thermodynamic calculations, three solution treatment temperatures of 475 °C, 500 °C, and 525 °C were determined, and the phase transformation under these temperatures were calculated and characterized, the results aligned well with experimental results. The optimal solution treatment technology was determined to be 500 °C for 18 h. After solution treatment, experimental alloys were subject to isothermal aging at 225 °C, the peak aging time for the experimental alloys was established. The microstructure under peak-aged state of the alloy was characterized, revealing a co-existed β’ and β1 phases. The GWZ1041K alloy, after peak aging treatment, exhibited optimal mechanical properties, with a tensile strength, yield strength, and elongation of 392.3 MPa, 249.3 MPa, and 5.7%, respectively. The study further analyzed the reasons for the microstructure transformation during the heat treatment and their influence on mechanical properties.

Microstructure and Mechanical Properties of a New TWIP Steel under Different Heat Treatments.

The effects of solution treatment and annealing temperature on the microstructure and mechanical properties of a new TWIP steel that was alloyed from aluminum (Al), silicon (Si), vanadium (V), and molybdenum (Mo) elements were investigated by a variety of techniques such as microstructural characterization and room tensile testing. The austenite grain size grew slowly with the increase in annealing temperature. The relatively weak effect of the solution treatment and annealing temperature on the austenite grain size was attributed to the precipitation of MC and M2C, which hindered the growth of the austenite grain. The plasticity of the TWIP steel in cold rolling and annealing after solution treatment was obviously higher than that in cold rolling and annealing without solution treatment. This was because the large-size precipitates redissolved in the matrix after solution treatment, which were not retained in the subsequently annealed structure. Through cold rolling and annealing at 800 °C after solution treatment, the prepared steel exhibited excellent strength and plasticity simultaneously, with a yield strength of 877 MPa, a tensile strength of 1457 MPa, and an elongation of 46.1%. The strength improvement of the designed TWIP steel was mainly attributed to the grain refinement and precipitation strengthening.

Microstructural evolution and mechanical properties of the rapidly-solidified and hot-extruded 2196 Al-Li alloy

The microstructural evolution and mechanical properties of the 2196 Al-Li alloy prepared by the vacuum gas atomization, hot-isostatic-pressing (HIP) and hot-extrusion were investigated. The results show that prior particle boundaries (PPBs) exist in the microstructure of the HIPed alloy, and hot-extrusion effectively breaks PPBs to restrict the element micro-segregations. The as-extruded alloy exhibits fine grains, and bears higher solution treatment temperature due to the absence of low-melting-point micro-segregations. In the ageing process, the alloy hardness continues to rise, and reaches the peak value at 48 h. The precipitation sequence of the alloy is determined to be: supersaturated solid solution (SSS) → GP zone + fine T1 + δ′ → T1 + θ′ + δ′, where T1 phase dominates the whole ageing process. The diameter of the T1 platelets increases gradually with the increase of ageing time, meanwhile the T1 number density slightly drops in the over-aged alloy. The 3% pre-stretching promotes the nucleation of T1 phase, and the peak-ageing time is shortened to 28 h. Besides, no over-ageing phenomenon is observed in the pre-stretched samples. The Mg-Cu and non-Cu clusters formed on the dislocations accelerate the precipitation of T1 phase and prevent the nucleation of θ′ phase. The yield strength (YS) and ultimate tensile strength (UTS) of the T8 sample are 490 MPa and 515 MPa, respectively, which is notably higher than the T6 sample. The tensile strength of the present alloy is relatively higher than that of the Al-Li alloys with a comparable Li content.

Electrochemical corrosion behaviour of UNS S32205 duplex stainless steel dependent on sigma phase precipitation

Abstract In this study, the microstructure and electrochemical corrosion behavior of the UNS S32205 alloy were investigated. Firstly, the phase diagram of the studied samples was determined by Thermo-Calc 2022 software, and the solution treatment temperature was designated. The studied samples were cooled by various cooling rates following the solution treatment at 1050 °C for 30 min. The samples were characterized by optical microscope, scanning electron microscope, and XRD analysis. Also, electrochemical corrosion behavior was investigated by potentiodynamic polarization, cyclic potentiodynamic polarization and electrochemical impedance spectroscopy analyses. Microstructural examinations revealed that decreasing cooling rate causes the precipitation of the sigma phase, and the ratio of the sigma phase was increased up to 29 % by the decreasing cooling rate. Furthermore, it was determined that precipitation of the sigma phase reduces the E pit values, and the sample with the highest amount of sigma exhibits the lowest corrosion resistance. On the other hand, presence of the sigma changed the electrochemical impedance spectroscopy behavior of the UNS S32205 and double-layered model fit the results.

Effect of heat treatment on microstructure and mechanical properties of Mg-6Gd-3Y-0.5Zr alloy fabricated by wire arc additive manufacturing

Heat treatment is necessary for GW63K (Mg-6Gd-3Y-0.5Zr, wt%) alloy fabricated by wire are additive manufacturing (WAAM) to improve the mechanical properties before final applications. Considering the unique solidification process and microstructure of WAAMed GW63K alloys, the heat treatment parameters must be different from the cast or forged ones. Thus, the present paper investigated the influence of solution temperature and time on the microstructure and mechanical properties of WAAMed GW63K, as well as the aging temperature and time. It was found that the as-deposited alloy exhibited fine equiaxed α-Mg grains with an average size of 13 μm and few eutectic phase Mg24(Gd, Y)5 around the grains. The proper temperature of solution treatment was 480℃ and the proper time was 0.5 h, lower and shorter than cast ones. After solution treatment, the average size of α-Mg grains almost remained the same and nearly all of the eutectic phase dissolved. To exert precipitation strengthening to a larger extent, we conduct aging treatment at 175°C, 200°C, and 225°C and draw their age-hardening curves. Besides, a superior strength /ductility trade-off was obtained peak aging at 200°C for 80 h, with the ultimate tensile strength of 337±8 MPa, yielding strength of 231±2 MPa, and elongation of 8.9±1.0%. This outstanding strength can be accounted for by the refinement strengthening of fine microstructure inherited from as-deposited GW63K alloy and precipitation strengthening from dense β′ precipitates with a remarkable plate aspect ratio. Besides, suitable β′ precipitates could support a favorable work hardening effect and compatible deformation capability.

Microstructural evolution and high-temperature strengthening mechanisms of the IN 738LC superalloy prepared by selective laser melting

Defect-free SLM-IN 738LC superalloy samples were fabricated using selective laser melting (SLM). The as-built samples exhibit a cellular structure with fine carbides, γ′ phases, and high-density dislocations at the cell boundary and nano-size γ′ phases in the interior, resulting in excellent deformation resistance and favorable mechanical properties at room temperature, with a yield strength (YS) of 970 MPa, an ultimate tensile strength (UTS) of 1263 MPa, and an elongation (EL) of 33%. This study investigates the evolution behavior of the γ′ phase at different solid solution treatment (SHT) temperatures and its impact on alloy strength and toughness. The 1020 + AHT sample exhibits a uniform distribution of coarse γ′ phases. The samples subjected to 1070 + AHT and 1120 + AHT display a bimodal distribution of γ′ phases. When the SHT temperature was further increased, fine spherical γ′ phases are evenly distributed in the 1160 + AHT and 1200 + AHT samples. Moreover, the γ/γ′ eutectics at the grain boundaries gradually dissolve with increasing SHT temperature, whereas the size and fraction of carbides increase. The room temperature tensile test of the 1070 + AHT sample demonstrated a favorable balance between strength and plasticity (YS = 1217 MPa, UTS = 1472 MPa, EL = 9.25%). This is attributed to the synergistic strengthening effect of the bimodal distribution of the γ′ phase. The temperature-dependent deformation behavior of the 1070 + AHT sample was analyzed at 23 °C, 800 °C, 900 °C, and 1000 °C. At 23 °C, numerous dislocations accumulated around the γ/γ′ interfaces. When the temperature increased to 800–900 °C, the dislocations shearing γ′ phases is activated and the alloy remained high strength. At 1000 °C, both the dislocation shearing and dislocation bypassing mechanisms coexist, resulting in a decrease in the strength of the alloy and an increase in its plasticity. This work provides scientific and theoretical support for SLM-IN 738LC parts with favorable properties.

Unraveling the effects of solution treatment on the microstructure and corrosion behavior of HT-HAZ in duplex stainless steel welded joints

Abstract In this work, the influence of solution treatment on the corrosion behavior and microstructure of HT-HAZ was studied. The results show that the balanced two-phase ratio is discovered after solution treatment. After solution treatment at 960°C, a small amount of chromium nitride remains at the two-phase interface and in the ferrite. With the solution treatment temperature increasing to 1120°C, chromium nitride can be fully dissolved. The chemical elements of the two-phase are redistributed during the solution treatment process, which results in changes in PREN. After solution treatment, the proportion of recrystallized grains increases whereas that of sub-structured grains decreases, indicating the reduction of residual stresses and deformations. The percentage of CSL boundaries increases as the solution treatment temperature rises. Compared with HT-HAZ without solution treatment, the improved corrosion resistance after solution treatment is ascribed to the balanced two-phase ratio, less chromium nitride precipitates, smaller residual deformations, and more CSL boundaries. However, the pitting resistance after solution treatment at 960°C is still relatively poor on account of the residual chromium nitride. The pitting nucleation sites are closely associated with the chromium nitride precipitates and PREN of two-phase.

Effect of Heat Treatment Temperature on Microstructure, Tensile Properties and δ-Precipitate Phase in Ni-based Superalloy

Here, we investigated the influence of δ-precipitate (orthorhombic D0a Ni<sub>3</sub>Nb-ordered phase) on the room- and high-temperature tensile properties in wrought nickel-based Inconel 625 superalloys subjected to solution and aging heat treatment. Typically, solution heat-treatment temperatures in these alloys affect the solid-state precipitation of δ-phase, which governs high-temperature tensile properties. While precipitation of fine D0<sub>a</sub> δ-phase is known to have beneficial effects on the mechanical properties owing to the retardation of grain coarsening, Widmanstätten δ precipitation plays a deleterious influence on the fracture toughness, tensile ductility, and fatigue resistance. Therefore, to enhance the mechanical properties of this alloy series, it is key to generate a high number density of fine D0<sub>a</sub> δ precipitate by adjusting solid solution treatment temperatures. In this study, solution heat treatments were conducted above and below δ-phase solvus temperatures. By applying solution heat treatment at 900°C and 970°C, this alloy was confirmed to have a Widmanstätten δ phase and is composed similarly to the annealed microstructure. This Widmanstätten δ precipitate was densely distributed at both intergranular and intragranular grains. On the other hand, when solution treatment was applied at 1040 and 1100°C, more coarse particles (approximately 30 μm) with a significant reduction of Widmanstätten type δ phase were obtained. We found that grain size and Widmanstätten δ-phases have an important role in the high-temperature tensile properties of Inconel 625 superalloy series.

Effect of Solution Treatment on Mechanical Properties of Inconel 718 Alloy Formed by SLM

Based on SLM forming process, Inconel 718 alloy powder material was used to design and print test parts, and the test parts were treated with solution treatment. This article explored the effects of solution treatment temperature and time on the mechanical properties of Inconel 718 alloy. The results indicate that the solution treatment can effectively improve the tensile strength, yield strength and density of the parts. When the solution treatment temperature increases, the material brittleness becomes larger, and when the solution treatment time prolongs, the material toughness improves. The density of the material increased with the extension of solution treatment time and the increase of temperature.

Optimization of duplex heat treatment settings with the MOORA-PCA technique to customize the mechanical and wear response of Ti6Al4V alloy

The impact of duplex heat treatment settings was examined to optimize the mechanical and wear responses of Ti6Al4V alloys. A multi-objective optimization using ratio analysis (MOORA) coupled with PCA was used to optimize the different outcomes. Heat treatment aims to reduce the wear rate, frictional coefficient, and improve tensile strength and microhardness. Variables like solution treatment temperature, duration, aging temperature, and time are considered for optimization. The optimization results reveal that the optimal circumstances are A3B1C2D3. The appropriate process parameter combination was finally evaluated by a confirmation test, which shows that the MOORA-PCA technique worked well together to find the best heat treatment settings. All of the heat-treated samples demonstrated better mechanical and wear characteristics. However, compared to other heat-treated samples, samples that underwent heat treatment in optimal settings have superior features. Compared to the heat-treated samples at trial 9 and the optimum conditions, the samples at trial 8 settings showed 5.4% and 12.3% lower microhardness, respectively. The alloy subjected to optimal conditions for heat treatment has a tensile strength of 1154.87 MPa, which is 12.95% and 6.09% greater than the specimen heat-treated at trials 8 and 9, respectively. Compared to the as-received alloy, the sample that underwent heat treatment at optimal settings exhibited a wear rate of approximately 40% lower than the as-received alloy, 3% lower than the heat treatment settings used in trial 8, and nearly 26% lower than the heat treatment settings used in trial 9. The bi-model microstructure developed under optimal circumstances is correlated with increased mechanical and wear properties.

Study of natural aging behavior of Al-0.4Mg-1.0Si alloy with the addition of Sn at different solution heat treatment temperatures

In this paper, the combined effect of Sn addition and solution treatment temperature on natural aging (NA) hardness behavior and microstructure of Al-0.4Mg-1.0Si alloy were investigated by hardness test, scanning electron microscope (SEM) and scanning transmission electron microscope (STEM). The evolutions of clusters characterized by three-dimensional atom probe (3DAP) during initials stages of NA are also investigated based on the slow in formation of clusters due to Sn addition. The results shown that a Sn-rich particles with round shape retained in Al matrix after quenching treatment when the added Sn content exceeds it limit solubility, which will reduce the Mg content of the designed alloy. The suppression of NA can be enhanced with the increase in the adding Sn content and solution treatment temperature, which is strongly related to the delay of the segregation of Mg and Si to form clusters due to more trapping vacancies by Sn atoms. The addition of Sn also revealed that the segregation of Si during NA is earlier than that of Mg atoms. The Si-rich clusters are formed preferentially during initial stage of NA, and Mg–Si co-clusters are formed after long period of NA. The Mg/Si ratio and average size of Sn-containing clusters in the 0.04%Sn and 0.1%Sn alloy are obviously higher than that of Sn-free clusters regardless of the 1 day NA or 14 days NA as more Mg atoms are dragged into Sn-containing clusters due to strong interaction between Sn and Mg atoms.

A novel low-cost Ti–Cr–Fe β-Ti alloy with TWIP effect: Sensitivity of tensile properties to microstructural characteristics

A novel low-cost Ti-4.6Cr–3Fe β-Ti alloy with twining induced plasticity effect was designed, and its tensile properties and deformation mechanisms were sensitive to its microstructural characteristic. The received sample with the microstructure of β matrix embedded isothermal ω (ωiso) precipitations exhibited the largest tensile strength (Rm), but the limited ductility (<3 %). When the solution treatment (ST) temperature increased from below to above α→β transition temperature, the microstructure changed from β matrix with αs precipitations to β matrix with athermal ω (ωath) precipitations, and the deformation mechanisms correspondingly changed from dislocation slip to the combination of dislocation slip and {332} deformation twins. Among different treatment samples, the ST800 sample obtained a relatively good combination of Rm (1146 MPa) and elongation to failure (EL, 12.5 %). It is surprising that, as the ST temperature increased from 800 °C to 900 °C, the Rm increased from 1146 MPa to 1230 MPa, but the fracture mode changes from ductile fracture to brittle fracture due to the formation of Laves phase (TiFe2) at grain boundaries. These findings provide a basis for improving the tensile properties of Ti-4.6Cr–3Fe alloy by adjusting the microstructure, and a reference for optimizing the composition of Ti–Cr–Fe system low cost β-Ti alloys.

Effect of Process Condition and Test Environment on Tensile Properties in Cold-Rolled Al-Cu-Mg Alloys

Severe plastic deformation processing and subsequent aging treatment have been known to be effective for achieving higher strength than the conventional aging treatment in aluminum alloys. This study prepared the Al-Cu-Mg-based alloy sample, Al-5.3Cu-2.8Mg (mass%). The alloys were solution treated at 480, 495 and 505°C, and cold-rolled by 90%. The effect of process condition and test environment on tensile properties in cold-rolled Al-Cu-Mg alloys was investigated. Results confirm that strength and ductility were improved with increasing the solution heat treatment temperature regardless of test environment. 0.2% proof stress and ultimate tensile strength were higher than aging treatment specimens, but elongation to failure was lower than aged one. Hydrogen embrittlement susceptibility increased with increasing solution treatment temperature. Ductile fracture with many dimples is observed in both cold-rolled and aged specimens. Second-phase particles were observed at the bottom of the dimples. There was no significant difference in fracture surface between the different test environments.

EFFECT OF HOT ROLLING AND SOLUTION TREATMENT ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF FE-MN-SI-CR-NI SHAPE MEMORY ALLOY

Fe-14Mn-4Si-8Ni-11Cr SMA (shape memory alloy) was designed as a smart material because of its specific properties, which can memorize the original shape, so it has the potential to dampen vibration in seismic structures. Memory effect is triggered by SIM (stress-induced martensitic) transformation from γ-austenite to ε-martensite (hexagonal close-packed / HCP) structure, and it is recovered by heating after unloading. This study investigated the effect of hot rolling and solution treatment on the microstructure and its relationship with hardness and SME (shape memory effect) properties. The as cast of Fe-14Mn-4Si-8Ni-11Cr was hot rolled (900 and 1000 ℃) and solution treated (1000 and 1100 ℃). After the thermomechanical process, all microstructures consist of γ-FCC (face-centered cubic), the annealing twins, and a fine band of ε-martensite. The grain size of the γ-phase is 29.43, 41.96, 42.44, and 45.57 μm for samples B, C, D, and E, respectively. The higher the temperature of hot rolling and solution treatment applied, the larger the grain size obtained, indirectly reducing the hardness to 299.93 BHN and 286.52 BHN for samples D and E. The coarsened austenite grain, a lower number of annealing twins, and the pre-existing line band of ε-martensite are favorable to obtain the enormous recovery strain, up to 8.26% for sample E.

Study on the role of solution treatment on corrosion behavior of duplex lightweight steel in different environments

Diverse microstructure and complex application environments increases the uncertainty of the corrosion resistance of lightweight steels. The effect of solution treatment on the corrosion behavior of Fe–16Mn–10Al–1.5C–0.1Ti lightweight steel in Cl−, HSO3− and Cl−–HSO3− environments was investigated using electrochemical measurement, scanning electron microscope (SEM) and X–ray photoelectron spectroscopy (XPS). The lightweight steels are dominated by austenite and contain a small amount of ferrite. The increase in solution treatment temperature leads to more ferrite formation, but it has less effect on grain size. The decrease in austenite content results in more corrosion microcells and a porous oxide film; therefore, the corrosion resistance of the steel deteriorates with increasing temperature. In addition, in the Cl−–HSO3− environment, the synergistic effect of Cl− and HSO3− leads to the formation of a weak protective oxide film, resulting in a significant increase in corrosion rate compared to the Cl−and HSO3− environment.

Analysis of cracking characteristics and mechanism of high-strength steel after chemical oxidation

The tooth surface of the 20CrNi2Mo worm underwent cracking after chemical oxidation. The appearance inspection results showed that there were multiple cracks on the tooth surface of the worm slice, and the direction of the cracks was perpendicular to the machining pattern. There were many microcracks on both sides of the main crack. The profile morphology shows that the crack depth reaches 1100 μm. The crack extends perpendicular to the tooth surface to a certain depth and then propagates in two transverse directions. After opening the crack on the tooth surface, observation shows that the overall section is black, and the artificially opened area is silver-white. At the interface between the artificially opened area and the initial fracture surface, the fracture surface changes from intergranular morphology to ductile dimple morphology. The energy spectrum shows that the oxygen content in the intergranular cracking area is much higher than that in the ductile dimple area, indicating that the worm has undergone intergranular corrosion cracking. After the worm tooth surface is ground, there will be certain tensile stress on the surface. During the chemical oxidation process, the worm will be exposed to many corrosive media such as OH−, and NO2 −. Under the combined action of tensile stress and corrosive ions, the tooth surface will undergo stress corrosion cracking. To effectively avoid cracking on the worm gear surface, three measures have been proposed to reduce the risk of cracking: (1) improving machining parameters to reduce grinding feed, (2) increasing destressing before chemical oxidation to reduce residual tensile stress, (3) improving chemical oxidation process to reduce solution concentration, treatment time, and treatment temperature.

The widening of the solution heat treatment window by the addition of Ru in Ni-based single crystal superalloy

This work investigates the effect of Ru on the solution heat treatment window of the Ni-based single crystal superalloy. The addition of the Ru influences the solidification microstructure and widens the window. The solidification process is established to occur in the sequence of γ (dendrite) → γ + γ' grid eutectic (inter-dendrite) → γ + γ' lamella eutectic (inter-dendrite) → γ' (inter-dendrite). This is followed by the γ → γ + γ' decomposition of the γ dendrite into the common channel-cuboid structure upon cooling. The solvus of γ' and the solidus of the alloy define the window. In alloys containing inter-dendrite eutectic, the window is in principle zero. In this case, only the dynamic window created by homogenization diffusion may allow heat treatment. Adding Ru decreases the elements' partition ratios between the dendrite core and dendrite edge regions. It also promotes the enrichment of Re at the γ/γ' phase interfaces, which helps to refine the γ + γ' channel-cuboid structure and reduce the differences in both the size and volume fraction of the γ' phase between dendrite core and dendrite edge. Ru is found to inhibit the formation of (Ta, X)C carbide. These help widen the solution treatment temperature window of the Ni-based single crystal alloy.

Influence of cooling strategy on microstructure, deformation mechanism and mechanical properties of a nickel-based superalloy

In this study, the influence of cooling strategy after solution treatment on microstructure and mechanical properties of a novel cast and wrought nickel-based superalloy is studied. It was found that continuous oil cooling (CC) from the solution temperature led to formation of large primary γ' and ultrafine tertiary γ'. Interrupted cooling (IC), which involves furnace cooling from the solution treatment temperature (1080 °C) to a lower temperature (such as 1010 °C, 980 °C or 950 °C) first followed by an interrupted oil cooling, shows significant influence on microstructure. Owing to a short-period furnace cooling, secondary γ' started to form in these interrupted cooled samples and their volume fraction and size increased continuously with decreased IC temperature. In contrast, the volume fraction of tertiary γ' decreased with decreased IC temperature. The CC sample was found to deform mainly by dislocation glide/climb and extension of stacking faults at 650 °C/950 MPa. With increased volume fraction of large secondary γ' in the interrupted cooled samples, deformation became increasingly planar, i.e., the formation of stacking faults and nanotwins increasingly became the dominant deformation mechanisms. The cooling strategy shows no obvious influence on tensile properties and impact toughness but shows significant influence on stress rupture properties. With decreased IC temperature and coarsened microstructure, the stress rupture lifetime continues to decrease.

Investigation of wt.% Si and Heat Treatment on the Mechanical Properties of Al6063 Aluminum Alloy by the Casting Product Propeller Shaft Model

Shaft propeller is one of the most important parts of ship propulsion installations. To produce a good quality shaft propeller, the ship propeller designer must consider various parameters, in order to produce the type and size of the propeller that has the value of effectiveness and high propulsion efficiency. Shaft propellers are usually made of steel but, in this study the propeller shaft model is made of Aluminum Alloy base material. So the material must have good mechanical properties. The purpose of this study is to see the mechanical properties of the sheller propeller with aluminum alloy base material with the addition of silicon elements and magnesium by going through the heat treatment process. The main base material used is 6063 aluminum alloy, with variations in the addition of Si (1, 2, 4 wt%). The addition of Mg can improve the mechanical properties of the casting. Alloy Al6063 is heated to a temperature of 790°C to reach a complete liquid state. Then the temperature is lowered to 645°C, then the Si element is inserted into the heating furnace and stirred. Then the temperature is lowered to 615°C, then the Mg element is added, then stirred thoroughly by a mechanical stirrer. The rotational speed of the stirrer is 70 rpm and the stirring time is 240 seconds. Then heated to a pouring temperature of 670°C. The mold is heated to a temperature of 265°C. Then poured into the mold and pressed 7 MPa. After that, it was allowed to stand for 600 seconds, and then removed from the mould. The cast propeller shaft is cooled at room temperature. Then the propeller shaft was heat treated with a solution treatment temperature of 485°C for 3600 seconds and then quenched using a fluid. After that, the casting products were treated with artificial aging. The results of the study are, Porosity will decrease along with the addition of Silicon elements. The lowest porosity level is in addition of 3% wt Silicon that is equal to 1.15%. Tensile test with the addition of 1% wt Silicon ie, 106.882 MPa, in addition of 2% wt Silicon that is, 128.713 MPa, and in addition of 3% wt Silicon ie 132.668 MPa. So the highest tensile stress value is at 3% wt. Hardness values will increase with the addition of Silicon elements. The highest hardness value found in the variation of 3% wt Silicon ie, 69.9 HB. While in the variation (0, 1, 2% wt) that is, 43.75 HB, 51.24 HB and 56.45 HB. So this study, proving that the addition of silicon elements can improve the mechanical properties of the shaft propeller.

Homogenization on solution treatment and its effects on the precipitation-hardening of selective laser melted 17-4PH stainless steel

17-4 precipitation-hardened (PH) stainless steel (SS) exhibits high strength and good corrosion resistance via Cu-precipitation hardening. Unlike conventional wrought 17-4PH SS, Cu segregation and ε-Cu precipitates are observed in additively manufactured (AM) 17-4PH SS owing to the repeated rapid cooling after heating, which characterizes the AM process. In this study, solution treatment was conducted under various temperatures (1,000, 1,050, 1,100, and 1,200 °C) and durations (1, 2, 4, and 8 h) to minimize the negative effects of Cu segregation and ε-Cu precipitates on precipitation hardening. The mechanical properties and microstructures of each condition for the Cu precipitation behavior were examined. Although the ε-Cu precipitates did not disappear after solution treatment, the average diameter of the ε-Cu precipitates tended to decrease with increasing solution treatment temperature and duration. Therefore, solution treatment at a temperature of 1,200 °C for 8 h was the best, resulting in improved strength compared to the conventional solution treatment at 1,050 °C. Solution treatment on at least 1,100 °C is effective in AM.