Water Quench Research Articles

Application of hot forming cold die quenching for facilitating equal channel angular pressing of AA2024 aluminum alloy

The effect of one pass hot forming cold die quenching (HFQ) in equal channel angular pressing (ECAP) on the evolution of hardness, tensile properties and microstructure of AA2024 aluminum alloy is investigated. Since AA2024 is a heat treatable aluminum alloy, it is sensitive to the cooling process applied before deformation or aging. Therefore, samples are considered in air cooled (AC) and water quenched (WQ) conditions and the results are compared with those obtained in HFQ-ECAP. In addition, hardness and tensile properties are investigated in as-deformed and aged conditions to understand the response of the alloy to aging. It is found that distribution of precipitates, hardness and tensile properties in the aged samples significantly depend on the cooling process prior to deformation. Significant increases in hardness (24 and 22%) and strength are observed when the WQ and HFQ samples are aged after one pass ECAP. However, an effective precipitation hardening is not achieved when AC cooling is applied. In addition, much more effective strengthening and precipitation hardening with respect to AC samples are observed by utilizing HFQ. Maximum hardness (201 Hv), yield strength (YS) (446 MPa) and ultimate tensile strength (UTS) (558 MPa) are achieved in the WQ sample after ECAP and aging treatment. Similar properties are achieved in HFQ-ECAP samples after aging treatment which respectively equal 190 Hv, 446 MPa and 560 MPa for hardness, YS and UTS. Indeed, due to its very similar achieved mechanical properties, the HFQ-ECAP is found as an effective way to replace WQ-ECAP of AA2024 alloy.

Step-Up Thermoelectric Performance Realized in Bi2Te3 Alloyed GeTe via Carrier Concentration and Microstructure Modulations

We report that outstanding thermoelectric performances can be achieved in 7% Bi2Te3 alloyed GeTe when it is simultaneously doped with iodine and treated with a water quenching process. The introduction of moderate iodine can help optimize the electrical properties; moreover, a water quench treatment was found to induce a novel vacancy microstructure, i.e., Ge vacancy “clusters”, which helps to modulate the thermoelectric performance at higher temperatures. The successful combination of these two strategies eventually results in a peak figure of merit ZT ∼ 2.2 at 723 K in water quenched Ge0.93Bi0.07Te1.005I0.03. This value is 2-fold of that in pristine GeTe (∼1.1). Corresponding average ZT between 323 and 773 K is 1.23, in comparison with 0.44 for pristine GeTe. The calculated single-leg device efficiency of water quenched Ge0.93Bi0.07Te1.005I0.03 is ∼11.2% at a temperature gradient from 298 to 773 K, suggesting GeTe is a very promising thermoelectric at intermediate-temperature range.

DAPO‐LLM‐105: Improving the Particle Morphology and Thermal Stability

AbstractA number of different quench media were evaluated in order to improve the characteristics of 2,6‐diamino‐3,5‐dinitropyrazine‐1‐oxide (LLM‐105) obtained via nitration of 2,6‐diaminopyrazine‐1‐oxide (DAPO). After a first screening phase, seven aqueous solutions containing a selected additive were used to quench the nitrating mixture in scale‐up experiments. Complete characterization of the resulting LLM‐105 indicated that nitrate salts as additives, especially ammonium and potassium nitrate, provided a high quality product, without requiring any further recrystallization. Notably, both particle morphology and thermal stability were significantly improved over the ones obtained using the standard pure water quench. This new DAPO‐LLM‐105 has been compared to the conventional DMP‐LLM‐105 and showed similar characteristics with even better insensitivity data.

The effect of cooling rate on the γ' composition, morphology and corrosion behaviour of IN738LC

The influence of γ' size and composition on the corrosion behaviour of IN738LC superalloy was investigated while maintaining a monomodal microstructure. Experimental results showed that smaller precipitates (∼50 nm), obtained by a rapid water quench (3000 °C/min), were spherical with an Al content of 6.2 wt.-%. Slower-cooled specimens (2.5 °C/min) exhibited larger cuboidal shaped γ' precipitates (∼800 nm) with reduced Al content (4.5 wt.%). Furthermore, a negative influence on the corrosion resistance of IN738LC was found with increasing rate of cooling, which is attributable to an increase in volume fraction and Al content of the γ' precipitates.

Effect of Temperature and Cooling Rates on the α+β Morphology of Ti-6Al-4V Alloy

Ti-6Al-4V is a dual phase (α+β) titanium alloy widely used in aerospace industry. Mechanical properties of a component strongly depend upon its microstructure and morphology. Desired mechanical properties can be achieved by the development of appropriate microstructure with the help of different heat treatments and deformation. In the present work, different microstructures obtained through different heat treatment processes are studied and presented. A variety of morphologies of α+β microstructure are obtained by heating above and below β transus temperature and cooling at different rates i.e. water quench, air cool and furnace cool. Heating above β transus and cooling with different rates results into lamellar structure whereas a duplex microstructure is obtained after heating below β transus and cooling with different rates. A lamellar structure with blocky acicular α is obtained after heating above β transus followed by furnace cool up to temperature below β transus and cooling with different rates. It is observed that cooling rate has a significant effect on hardness of heat treated sample. Faster cooling results in higher hardness.

Sustainability of friction stir welded AA6082 plates through post-weld solution heat treatment

Abstract There is high demand for a novel fabrication technique that requires low energy consumption rate for its operation, environment-friendly and sustainable. The aforementioned attributes make friction stir welding (FSW) to be globally accepted in joining aerospace alloys that are difficult to weld using the conventional arc welding technique. In this investigation, friction stir welds were processed plastically and characterized thermo-mechanically. Also, three welding speeds i.e. 90 mm/min, 120 mm/min and 150 mm/min were adopted using tool-rotational speed 950 rpm and 1150 rpm respectively. An attempt was made to investigate the effect of severe plastic deformation and solution heat treatment on the tensile property of the welds. A solution heat treatment temperature of 4700C for 30minutes, held for 30 another minutes and water quench. The mechanical properties of the welded joints after solutionizing was linked to the sustainability of FSW process. A maximum tensile strength (UTS) of 100 MPa for the as-weld specimen and 233.5 MPa after post-weld heat treatment were recorded at welding parameter 150mm/min and 950 rpm respectively. Meanwhile, the higher the weld-pitch (mm/rev) and the heat input (J), the softer the weld joints and the lower the UTS. Aside from point of fracture which were observed to be at the thermo-mechanical zone (TMAZ), the disparities in composition evolution and physical features of all the welded joints were similar. In conclusion, solution heat treatment improved the weld strength as well as the ductility. The improved value of UTS through solution heat treatment makes the weld joints reliable and FSW a sustainable process.

Extrusion Benchmark 2017: Effect of Die Design on Profile Quality and Distortions of Thin C-Shaped Hollow Profiles

The Extrusion Benchmark 2017 is focused on the evaluation of different die design strategies for the production of two AA6005A thin C-shaped hollow profiles. The process was monitored in term of press load, profiles speed, profiles exit temperature, die temperatures (with specific focus not only on the die but also on the external die ring) and die deflection. Extruded profiles were analyzed in term of geometrical tolerances, microstructure evolution and profile distortions for both air and water quench; the profiles were also be analyzed for retrieving seam welds positions and charge welds extent.

Interactive study on phase morphology and mechanical characteristics of diffusion annealed and age hardened Al7075–steel powder reinforced metal matrix composites

This paper expounds the effects of diffusion annealing and age hardening heat treatments on the phase morphology and mechanical properties of Al7075–eutectoid steel powder (0.8 wt% carbon steel) reinforced composites. Eutectoid steel powder ranging from 55–70 μm is selected due to its ability to improve the bulk hardness of the composite. In the present study three different weight fractions of eutectoid steel powder composites are prepared by conventional stir casting process. The material is cast in the form of rods inside the permanent stainless steel mould from where some samples are cooled in still air to room temperature. From these samples some are diffusion annealed from isothermal holding of 6 h i.e., above recrystallization temperature (600 °C) followed by boiling water quench and few are subjected to age hardening for a fixed time duration of five hours. Age hardening is carried out at solutionising temperature 560 °C tailed by aging at two temperatures 100 °C and 180 °C independently. All the samples in each category are subjected to critical property characterization and the phase arrangement information are characterized by scanning electron microscopy. From the analysis of microstructure and destructive tests, it is clear that the as-cast (stir-cast) samples display dendritic segregations with wider grain boundary area, is responsible for the inferior mechanical properties. It is also found out that diffusion annealing and age hardening heat treatments eliminates micro-segregation and improve mechanical properties of Al7075–eutectoid steel powder reinforced composites. It is concluded that chemical inhomogeneity in dendrites can be eliminated by selecting the suitable heat treatment with proper heat treatment parameters.

Ductility Improvement Mechanism of Pure Titanium with Excessive Oxygen Solid Solution via Rapid Cooling Process

Oxygen solid solution has been well known to have a high hardening effect on Ti and its alloys, while it also imposes a serious embrittlement behavior. This study investigated the effect of a rapid cooling process by water quenching (WQ) after heat treatment on the microstructures and mechanical properties of powder metallurgy (PM) α-titanium (Ti) materials with dissolved 0.94 mass% oxygen (O) to clarify their ductility improvement mechanism. The water quenching was applied to PM Ti extruded rod after isothermal annealing at 1173~1373 K. Tensile test results at the ambient temperature indicated that the elongation to failure of the quenched ones at 1223 K and 1273 K was 12.5% and 19.1%, respectively. They are significantly higher than that of as-extruded Ti specimen (6.0%). The Ti-0.94 mass% O materials via the above WQ treatment mainly consisted of equiaxed α-Ti grains, and some martensite phases were also detected at the grain boundaries. They were formed from β phases during phase transformation during WQ due to a lower oxygen content in pre-β phases compared to pre-α phases. The pre-β phase also had a high concentration of dislocation after tensile test. The significantly increased elongation was due to a lower oxygen content phase formation assuming an important role to improve the plastic deformation ability.

Water Quenching of Hot-Rolled Aluminum Strips: Process Integrated Heat Treatment of the Alloy EN AW-6082

Hot rolling of thin sheets of hardenable aluminum alloys with integrated quenching allows the coupling of both deformation and heat treatment into a single processing step, analogous to hot extrusion. However, unlike hot extrusion, hot rolling is performed in a lower temperature range as a result of material contact with the unheated forming tool during deformation. The influence of this type of processing on mechanical properties has rarely been studied. In the present work, the effect of the individual parameters of hot rolling with integrated heat treatment on the microstructure and mechanical properties of alloy EN AW-6082 has been studied. The results have been compared with similarly heat-treated unworked material. It has been revealed that hot rolling can cause the strength of the material to deteriorate after final natural and artificial aging, leading to a failure to fulfil the requirements of standards. Finally, recommendations for decreasing the above-mentioned negative influence have been proposed.

Effect of post-process heat treatment on microstructure and properties of selective laser melted AlSi10Mg alloy

In the present work, the model alloy of AlSi10Mg was prepared by selective laser melting, and further annealed by two kinds of heat treatment regimes, i.e. A1 (300 °C/2h+ water quench) and A2 (535 °C/1h+ water quench + 190 °C/10 h+ furnace quench). The samples were investigated by XRD, SEM, EBSD, room temperature tensile and nanoindentation tests, to understand the effect of heat treatments on the phase constituents, microstructure, residual stress and mechanical properties of the laser additive manufactured AlSi10Mg alloy. The experimental results showed that, the heat treatment method of A1 is an effective heat treatment regime for eliminating the residual stress and improving the comprehensive mechanical properties for structural applications.

Phase Transformation Behavior of a β-Solidifying γ-TiAl-Based Alloy from Different Phase Regions with Various Cooling Methods

The phase transformation behavior of Ti-42Al-5Mn (at.%) alloy from different phase regions with various cooling rates was investigated based on electron probe micro analyzer-backscattered electrons (EPMA-BSE). It is shown that β→α2′ takes place when this alloy is cooled at a high rate, such as water quenching (WQ), oil cooling (OC), from β single phase. With the decreasing cooling rate to air cooling (AC), β→α2′ is restrained and β→γ is promoted by forming γ platelets. The room-temperature microstructure is βo + α2 when alloy cooled (WQ and OC) from (β + α) dual-phase. However, under AC, β→γ occurs and γ platelets form. It should be noted that α2→γ happens when this alloy cooled from 1180 °C (>Teut) by OC and AC, forming an incomplete lamellae (α2/γ) structure in the α2 phase. However, when the alloy cooled from 1100 °C (<Teut), α2/γ→βo,sec occurs and complete lamellae generates in α2 phase.

Origins of different tensile behaviors induced by cooling rate in a near alpha titanium alloy Ti65

The influence of cooling rate after solution treatment on tensile behaviors of a near α titanium alloy Ti65 at test temperature from room temperature (RT) to 650 °C was investigated. The results show that tensile elongation and area reduction for water quenched (WQ) microstructure are 55% and 89% higher than those of air cooling microstructure tested at 650 °C, while yielding/ultimate strength are 613/743 MPa, around 8% higher than those of air cooling (AC1) microstructure. With the increase of test temperature, strength and ductility were both dramatically improved in water quenched (WQ) microstructure compared with air cooling (AC1) microstructure. This phenomenon was primarily attributed to the distinction of microstructure morphologies induced by cooling rates. The origin of differences of tensile behaviors between air cooling (AC1) and water quenched (WQ) microstructures is discussed in terms of microstructure morphologies, grain orientation dependency, tensile fracture surfaces, and the role of twining. The schematics of tensile fracture modes are proposed for air cooling and water quenched microstructures tested at room temperature and 650 °C.

Thermodynamic analysis on molten slag waste heat cascade recovery method (MS-WHCR)

Thermal energy recovery of pyrometallurgy slags is a worldwide problem that is widely concerned for decades. As chemical recovery method, molten slag cascade recovery method (MS-WHCR) is proposed in this work. As typical endothermic chemical reactions, pyrolysis, gasification, calcination and reforming reactions are applied in this method. Gasification–pyrolysis system, calcination–pyrolysis system, enhanced pyrolysis system (R-SEP) and fixed carbon gasification and sorption-enhanced pyrolysis system (CG–SEP) systems of MS-WHCR method are designed. Based on the first law of thermodynamics and second law of thermodynamics, enthalpy–exergy compass analysis method is applied to analyze the exergy efficiency, consumption of reactants and products of designed MS-WHCR method, compared with traditional water quenched (WQ) method and gravity bed waste heat recovery (GWHR) method. As calculation example, 1000kg copper slag is used in this paper. The results showed that the exergy efficiency and exergy loss of WQ method are 20.7% and −947 MJ respectively. By WQ method, energy quality of molten copper slag is discounted. Copper slag particles should be fast cooled during granulation process. Thus, lots of air is blown in to make enough heat transfer with copper slag particles, which generate some exergy loss. And exergy efficiency of GWHR method is 76.9%. Using chemical endothermic reactions, MS-WHCR method improves the exergy efficiency of molten slag waste heat recovery. There is a slight fluctuation of exergy efficiency by MS-WHCR method for four kinds of systems from 66.6 to 70.1%. Fixed carbon and combustible syngas are acquired by MS-WHCR. And enhanced pyrolysis process in proposed R-SEP and CG–SEP systems improves hydrogen contents in syngas.

Study of Opto-Mechanical Properties of Tubular Water Quenched Polyethylene Films

Tubular Water Quench (TWQ) is commonly used process to make Polypropylene based films (TQPP). This process has been tried for the first time to make Polyethylene films (TQPE) from HDPE-LLDPE blend. Polyethylene inculcates the inherent materialistic property of softness and better feel to the film. The key requirement for TWQ films are Openability and transparency. This paper focuses on novel developmental work done, using Polyethylene blend for making TQPE film, comparing it’s optical and mechanical properties with TQPP films.

Finite Element Wear Behaviour Modeling of Super duplex stainless steel AISI 2507 Using Ansys

In this paper the finite element simulation approach has been employed for the work that has been recently carried out by Davanageri et al.(2017). The super duplex stainless steel AISI 2507 material was heat treated at 850°C with different ageing time (30, 60, 90 minutes), followed by water quench. The heat treatment was carried out to encourage the precipitation of inter-metallic secondary sigma phase (σ). The study of dry sliding wear behavior was carried out with the pin-on-disc equipment. The heat treatment and ageing time increases the hardness of the duplex steel, resulting in improved wear resistance. The Archard wear model and finite element software ANSYS WORKBENCH-16 was used to determine the wear volume loss. The specific wear rate or dimensional wear coefficient is the most significant factor in the wear volume calculation and it varies with material and operating parameters. The study shows that frictional coefficient varies with material properties (hardness) at similar operating condition. Finally the results reveal that there is a good agreement that exists between the simulated (FE) values and those of the experimental values.

Numerical Simulation of Water Quenching of Large Size Steel Forgings: Effects of Macrosegregation and Grain Size on Phase Distribution

In this paper, water quenching of large ingots was simulated using FORGE NxT 1.1® Finite Element code. Simulations were carried out for as-forged medium-carbon low-alloy steel. A novel method is proposed to simulate the different parts of a large size forged block with different chemical compositions and grain sizes using the multiple materials method. The effects of macrosegregation, grain size variation and cooling rate on phase distribution through the volume of the forged block were investigated. The delay in transformation kinetics, which is due to the effect of grain size variation and carbon content, was analyzed. Results show that macrosegregation and grain size variations significantly influence transformation start points and the volume fraction of phases that are present in each location of the forged ingot. The proposed prediction method was validated using high-resolution dilatometry experiments and X-ray diffraction measurements to evaluate accurately the volume fraction of martensite, bainite and the percentage of retained austenite for each condition.

Weld joint design and thermal aging influence on the metallurgical, sensitization and pitting corrosion behavior of AISI 304L stainless steel welds

Experimental investigations were carried out to study the influence of weld joint design and post weld thermal aging treatments on the metallurgical, intergranular and pitting corrosion behavior of AISI 304L stainless steel welded joints. 10 mm thick linear weld joints were fabricated using gas metal arc welding process using single-V and double-V joint design with an average heat input of 503.42 J/mm and 562.78 J/mm respectively. Thermal aging of these welds was carried out at 750 °C for 0.5 h and 4 h, and the cooling media used was furnace, air and water quench (used separately for each specimen), so as to induce variable degree of carbide precipitation in different zones of these welds. Microstructural studies revealed that the extent of carbide precipitation was more in case of welds made using double-V joint design as compared to single-V joint welds. Degree of sensitization (DOS) and pitting performance of these welds evaluated using double loop electrochemical potentiokinetic reactivation (DLEPR) technique and potentiodynamic anodic polarization technique respectively, further showed that single-V joint performed better in terms of corrosion properties owing to lesser precipitation as compared to the double-V joint. This study shows that in comparison to double-V joint, single-V joint design can prove to be an important part of fabrication procedures where service conditions demand better corrosion properties of these welds.

Mechanical response of ultra-high strength (Grade 1200) steel under extreme cooling conditions

Ultra-high strength steels (UHSS) with nominal yield strength of up to 1200 MPa have many potential applications in engineering fields. However, due to inadequate knowledge on the mechanical behaviour of these materials under extreme loading conditions (e.g. severe temperature changes), their extent of application in civil construction has remained restricted. This paper characterises the mechanical properties of Grade 1200 UHSS under extreme cooling conditions, which is defined as cooling from fire temperatures with an extreme cooling rate or cooling from ambient state to sub-zero temperatures. In order to simulate the extreme cooling rate, UHSS standard dog-bone specimens are heated up to different fire temperatures and cooled to room temperature using water-quenching (WQ) technique. To evaluate the effect of extreme cooling rate on the post-fire mechanical response of the tested materials, the residual mechanical properties of water-quenched specimens are compared to the air-cooled (AC) ones for different fire temperature exposures. For simulation of extreme cooling temperatures, the test specimens are cooled to sub-zero temperatures using Liquid Nitrogen (LN) injection. The changes in the mechanical properties of the tested specimens are then quantified and discussed. In both set of experiments, the mechanical behaviour of UHSS under extreme cooling conditions is compared to the common structural steels. Microstructural evaluation of UHSS tested specimens are also presented using optical and scanning electron microscopy (SEM) techniques.

Processing, microstructure and mechanical properties of in-situ Ti3Al+TiAl matrix composite reinforced with Ti2AlC particles prepared by centrifugal casting

The samples of in-situ α2(Ti3Al) + γ(TiAl) matrix composite reinforced with Ti2AlC particles were prepared by a centrifugal casting of Ti-46.4Al-5.1Nb-1C-0.2B (at.%) alloy. The microstructure of the as-cast samples consists of equiaxed nearly lamellar α2 + γ grains with ribbon like TiB particles formed in the interdendritic region and homogenously distributed plate-like Ti2AlC particles distributed preferentially within the dendrites. The solution annealing of the samples in the α (Ti-based solid solution) phase field and subsequent air cooling (AC), oil quenching (OQ) and water quenching (WQ) leads to the formation of massive γM(TiAl). The subsequent annealing in the γ phase field followed by a stabilisation annealing at 900 °C leads to the formation of homogeneous fine-grained γ type of microstructure in the OQ and WQ samples. The solution annealing of the OQ and WQ samples in the α phase field followed by slow cooling results in the formation of equiaxed grains with nearly lamellar α2 + γ microstructure. The Vickers hardness and indentation elastic modulus strongly depend on the applied heat treatments. The in-situ composite with the coarse-grained lamellar microstructure shows improved creep resistance compared to that of some TiAl-based alloys with fully lamellar, nearly lamellar, convoluted or pseudoduplex microstructure.