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The mechanical properties of age-hardenable Al-Si-Mg alloys depend on the rate at which the alloys are cooled after the solutionizing
heat treatment. Quench factor analysis, developed by Evancho and Staley, was able to quantify the effects of quenching rates
on the as-aged properties of an aluminum alloy. This method has been previously used to suc...
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It has been over 55 years since Fink and Willey introduced the first TTP curves for aluminum alloys and 35 years since Staley and Evancho developed quench factor analysis (QFA) and applied it successfully to predict properties of heat-treatable aluminum alloys. There have been many studies on the use of TTP curves in property prediction for differe...
Time-temperature-precipitation (TTP) diagrams deliver important material data, such as temperature and time ranges critical for precipitation during the quenching step of the age hardening procedure. Although the quenching step is continuous, isothermal TTP diagrams are often applied. Together with a so-called Quench Factor Analysis, they can be us...
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... Therefore, studies have been conducted to optimize the cooling conditions in terms of the cooling rate and quench sensitivity. 1,6,[13][14][15][16][17][18] Zhang et al. 13) reported in detail the mechanical properties and microstructure of A356 alloy that was cooled using rates in the range of 250°C/s to 0.5°C/s immediately after solution treatment. Specimens cooled at 0.5°C/s showed 27% lower tensile strength and 33% lower proof stress after artificial aging compared to those cooled at 250°C/s. ...
The objective of this study was to optimize the cooling conditions after solution treatment of the JIS AC4CH aluminum casting alloy, and the effects of the temperature range cooled at 0.5°C/s on the microstructure and mechanical properties were investigated. The temperature range of the cooling and cooling rate were simultaneously adjusted by heating using a high-frequency induction heating apparatus and cooling by blowing air. In particular, cooling at 10°C/s (CR10) was used as the basic cooling rate, with a rate of 0.5°C/s (CR0.5) used for a portion of the temperature range. The scanning electron microscopy (SEM) observations of the specimens after cooling revealed that rod-like precipitates formed in the specimens that were cooled at CR0.5 in the range of 400–250°C. In the specimen that was cooled at CR0.5 from 500 to 450°C, granular or rod-shaped precipitates with a small aspect ratio were observed. From the results of a scanning transmission electron microscopy with energy dispersive X-ray spectroscopy (STEM-EDS) investigation, the former were identified as the Mg2Si intermediate phase, and the latter were composed mainly of Si. An electron probe micro analyzer (EPMA) was used to measure the Mg and Si concentrations in the primary α-Al phase. In the case of the temperature range for CR0.5 cooling above 350°C, the Si concentration decreased significantly as the temperature range of CR0.5 cooling increased. Considering the Si concentration distribution and diffusion distance in the primary α-Al phase, this decrease in the Si concentration could have been caused by the diffusion of Si atoms to the eutectic region. The 0.2% proof stress and tensile strength values after the artificial aging of a specimen that was cooled at CR0.5 from 400 to 350°C, where a coarse Mg2Si intermediate phase precipitated during cooling, were approximately 10% lower than those of a specimen that was cooled at CR10 over the whole temperature range.
Effects of temperature range cooled at 0.5°C/s (CR0.5) on microstructures and mechanical properties. Fullsize Image
... Numerous technical parameters assessment systems, including nozzle diameter, spray height, and sample size, which are suitable for an Al alloy hardenability test device, are not systematically and completely established to the field of hardenability evaluation of high-performance Al alloys [13,14,28,29]. Before quenching, the technological process and quenching fixtures differ from actual production, making it impossible for typical industrial quenching to accurately represent the quenching properties by the data obtained from the quenching cooling process [30]. The end-quenched sample was air quenched at one end while water-quenched at the other, which caused a discrepancy in the sample's hardenability statistics. ...
... Table 1. The technical parameters details of the traditional end-quenching method for the hardenability testing of alloy [9,10,13,14,[21][22][23][24][25][26][28][29][30]34]. ...
In this paper, the progress of the test methods and characterization approaches of aluminum alloys hardenability was reviewed in detail. The test method mainly included the traditional end-quenching method and the modified method. While the characterization approaches of alloy hardenability consist mainly of ageing hardness curves, solid solution conductivity curves, ageing tensile curves, time temperature transformation (TTT) curves, time temperature properties (TTP) curves, continuous cooling transformation (CCT) curves, and advanced theoretical derivation method have appeared in recent years. The hardenability testing equipment for different tested samples with different material natures, engineering applications properties, and measurement sizes was introduced. Meanwhile, the improvement programmed proposed for shortcomings in the traditional hardenability testing process and the current deficiencies during the overall hardenability testing process were also presented. In addition, the influence factors from the view of composition design applied to the hardenability behaviors of Aluminum alloys were summarized. Among them, the combined addition of micro-alloying elements is considered to be a better method for improving the hardenability of high-strength aluminum alloys.
... It is well known that the SDAS value is controlled by the solidification parameters such as thermal gradient, solidification velocity, and freezing rate and can be calculated based on different models [17,18]. Depending on heat treatment conditions different precipitates such as β ′′ (Mg 2 Si), βʼ (Mg 2 Si), and β(Mg 2 Si) can appear [19]. Both phenomenological and physical approaches have been developed for modelling and predicting the precipitation hardening in cast Al-Si alloys [20][21][22]. ...
... Ma et al. [13] studied the effects of the process parameters like polymer concentration and agitation) on the quenching behaviour of cast aluminium alloy A356 in the aqueous solution of Aqua-Quench 260 using the CHTE quenching-agitation system. It is found that the average cooling rate gradually decreases with the increase in polymer concentration. ...
Aluminium is an important engineering material that is widely utilized due to its suitable mechanical properties in manufacturing industries. The effectiveness and efficiency of cast aluminium alloy depend greatly on various casting methods. The additives in the sand mould and quenching media contributed to perfect casting. Present study investigated the influence of various sand mould additives (Sawdust Ash, Groundnut Shell Ash, and Eggshell Ash) on the tensile properties of the cast Aluminium (6061) alloy cooled in different media (Water, Palm Oil, and Engine Oil). The additives were varied at 5%, 15%, 25% and 35%. After cooling, the samples were subjected to a tensile test and the result showed significant differences in the tensile strength properties of the cast samples. Ultimate tensile strength values increased as the percentage of additive in sand mould increased. However, for all the additives studied, water had the highest ultimate tensile strength values (107.52 MPa, 100.5 MPa and 94.55 MPa) followed by palm oil and engine oil at 25% but decrease at 35%. Percentage elongation values of the samples decreased with an increase in additives ratio up to 25% but had the highest values when quenched in engine oil. These observed behaviours are attributed rate of solidification the moulds and cooling rate behaviours of the media.
... The time needed to spheroidise the eutectic Si insistently depends upon the temperature. Mama et al. [27] suggested that the ideal time and temperature for solutionising depends upon the projecting methodology, the level of change, coarsening of silicon particles, and level of spheroidisation. An investigation done by Ishak et al. [25] demonstrated that the most outrageous temperature for solution treatment of metal should not outperform, at whatever point the circumstance permits, its solidus temperature. ...
The current work is focused to ascertain the impact on the mechanical and morphological characteristics of hypoeutectic alloy Al–Ni with a range of solution treatment temperatures. Al, Ni, Si, and Mg of necessary weight percentages were melted in a crucible (make–clay graphite) and were cast. The cast alloys were then solutionised for 8 h from 450 to 550 °C, quenched and was aged for 12 h at 170 °C. The fractography, intermediate phase and the elementary composition of alloy was determined. It was observed from the investigation that a rise in solutionising temperature caused grain refinement in the developed hypoeutectic alloys. A surge in the value of hardness was observed with respect to the rise in solutionising temperature. It was also noticed from the analysis that the value of tensile strength, yield strength, ductility and impact resistance of the hypoeutectic alloys enhanced with temperature rise from 480 to 510 °C and then declined from 510 to 550 °C.
... As the quench rate decreases from 250 ºC/s to 0.5 ºC/s, the ultimate tensile strength and yield strength of peak-aged A356 castings decreased by approximately 27 and 33%, respectively. Ma et al. [7] used the quench factor analysis method to predict the effect of quench rates on mechanical properties of A356 PM castings, and the predicted results were in good agreement with the experimental data. Recently, Liu et al. [8] investigated quench sensitivity of AlSi10MnMg PM and HPVD castings. ...
The quench sensitivity of an AlSi7MnMg alloy in high-pressure vacuum die (HPVD) casting was investigated by time-temperature-transformation and time-temperature-property diagrams with an interrupted quench technique. The quench sensitive temperature range of the alloy is from 260 to 430 °C and its nose temperature is 350 °C. The mechanical strength versus cooling rates of the HPVD casting was predicted using quench factor analysis method and verified by experimental results. The critical cooling rate is 6 °C/s to remain 95% of the maximal mechanical strength. The coefficients k 2 - k 5 , related to the nucleation and precipitation kinetics of TTP curves, and phase transformation diagrams were determined. The precipitation of Mg 2 Si phase in the castings was observed during isothermal treatment using transmission electron microscope. Moreover, the quench sensitivity and kinetics of the phase transformation of AlSi7MnMg alloy and AlSi10MnMg alloys were compared. It reveals that the quench sensitivity and phase transformation rate of the former are lower than that of the latter.
... In addition, water and water-based liquids are the fastest quenching media due to their fastest cooling rate, which in turn results into high hardenability values and outstanding mechanical properties of the materials. Although, they possess high consistent cooling rate during quenching process, however; they can also cause problems like distortion and cracking due to high thermal gradients induced upon cooling [12]. The first quenchant developed as alternative to water and water based quenchants was petroleum-based quenching oil around 1880 by Houghton in Philadelphia. ...
Heat treatment industries require various quenching media to improve the properties of the materials to be quenched. Petroleum based mineral (PBM) oil, a non-biodegradable oil, is popular amongst other
quenchants in heat treatment processes. Recently, biodegradable oils mostly in their raw, unblended and unbleached forms have been employed for quenching of various engineering materials. Therefore, the present study examined the effects of some selected bio-quenchants in blended raw (BR) and blended bleached (BB) forms on the mechanical properties and microstructure of solution heat treated aluminum (Al)-alloy. Edible vegetable oil (70% by volume) was blended with 30% by volume of jatropha oil to form the bio-quenchant oils. Another set of bio-quenchants were formed by bleaching the raw oils before mixing so as to reduce the oxidation level and contaminations in the oil. The Al-alloy is solution heat treated at 5008C and soaked for 15 min in an electric muffle furnace before quenching in the various established bio-quenchants. Results showed that samples treated in blended raw melon(BRM) oil have higher tensile strength of 151.76 N/mm2while samples quenched in blended bleached melon (BBM) oil have higher hardness value of 61.00 HRC. In accordance to the results obtained the bio-quenchants were found to be effective replacement to the PBM oil.
... This parameter is commonly obtained by experimental testing and the inverse method [10]. The method of using a simple heat transfer coefficient model to account for quenchant side heat transfer has been widely adapted in FEA method [11] to predict residual stress and it is referred as "HTC method." Equation (5) and (6) can be greatly simplified to a form that can be solved analytically if we make the following assumptions: 1) no latent heat release during quenching process, 2) the temperature gradient is infinitesimally small in the metal so that metal temperature is uniform and is a function of time only, 3) heat transfer coefficient is uniform on the surface so that it is only a function of surface temperature (which could be a function of time). ...
For steels and aluminum alloys, liquid quenching is the most effective method to achieve fast cooling rates. In the example of water quenching an aluminum 319 cylinder head, the temperature drops rapidly within 30 seconds from solutionizing temperatures at 495 °C to water pool temperature below 100 °C. In this temperature range, the water boiling in the quenching process goes through three boiling regimes, film boiling, transition boiling and nucleate boiling, before reducing to convection heat transfer. Since each boiling regime has unique heat transfer characteristics that are governed by different physics, modeling the water quenching processes by computer simulation requires a heat transfer framework, instead of just a few equations, that can describe all the boiling regimes. Among several heat transfer frameworks found in the literature, we had successes in developing a CFD methodology to simulate the boiling process by adapting a heat transfer framework based on Leidenfrost point (LFP), minimum heat flux (MHF) and critical heat flux (CHF). This CFD methodology, when integrated with FEA structural analysis, is the key enabler for virtual process verification. This is achieved by first calculating temperature histories and profiles in CFD and then applying the temperature data as thermal load to FEA to predict thermal residual stress and distortion. Although the LFP, MHF and CHF framework have been proven useful to model the water quenching process, these parameters are not constants and they have to be calibrated through experiments for each quenching condition. The objective of this paper is to develop a consistent method to calibrate the boiling heat transfer framework using cooling curves obtained by the ASTM D6200 quenchometer. Also included in this paper is a preliminary discussion on broadening the standard in order to support: (1) generic cooling curve characteristics for any quenchant, (2) the analytical cooling curve for computation model calibration.
... In Figure 9, the results of two different orientations are compared [26]. Racking a part so that it enters the quenchant smoothly also offers the benefit that of more uniform heat transfer across the part [27]. Distortion is more likely to occur because of horizontal changes in heat transfer than by vertical differences in heat transfer. ...
... In Bild 9 werden die Ergebnisse zweier unterschiedlicher Ausrichtungen verglichen [26]. Das gleichmäßige Einbringen eines Teils in das Abschreckmedium bietet auch den Vorteil eines gleichmäßigeren Wärmeübergangs auf das Teil [27]. Es ist wahrscheinlicher, dass aufgrund horizontaler Änderungen der Wärmeübertragung Verformungen auftreten als aufgrund vertikaler Unterschiede der Wärmeübertragung. ...
The heat treatment of aluminum (Solution Heat Treatment, Quenching and Aging) are critical processes to insure that the desired mechanical and corrosion properties are achieved. Of these steps, quenching is perhaps the most critical of all the operations. If quenching is too fast, properties are met, but the part may have excessive distortion or residual stresses. This can result in shortened life due to residual stresses, or result in additional non-value added straightening of the component and this increases cost and cycle time. In this paper, the mechanism for distortion of aluminum is explained, and methods (racking and quenchants) are shown that can reduce distortion and residual stresses in heat treated components.
... Besides continuous cooling, quenching to various isothermal soaking temperatures has also been frequently applied, again in combination with a subsequent property analysis, which allows isothermal time-temperature property diagrams to be derived, for instance [10,18,23,54]. In order to allow evaluation of continuous cooling basing on isothermal experiments, the quench factor analysis method was developed [20] and refined [47,48,52,[55][56][57][58]. ...
For aluminium alloys, precipitation strengthening is controlled by age-hardening heat treatments, including solution treatment, quenching, and ageing. In terms of technological applications, quenching is considered a critical step, because detrimental quench-induced precipitation must be avoided to exploit the full age-hardening potential of the alloy. The alloy therefore needs to be quenched faster than a critical cooling rate, but slow enough to avoid undesired distortion and residual stresses. These contrary requirements for quenching can only be aligned based on detailed knowledge of the kinetics of quench-induced precipitation. Until the beginning of the 21st century, the kinetics of relevant solid-solid phase transformations in aluminium alloys could only be estimated by ex-situ testing of different properties. Over the past ten years, significant progress has been achieved in this field of materials science, enabled by the development of highly sensitive differential scanning calorimetry (DSC) techniques. This review presents a comprehensive report on the solid-solid phase transformation kinetics in Al alloys covering precipitation and dissolution reactions during heating from different initial states, dissolution during solution annealing and to a vast extent quench-induced precipitation during continuous cooling over a dynamic cooling rate range of ten orders of magnitude. The kinetic analyses are complemented by sophisticated micro- and nano-structural analyses and continuous cooling precipitation (CCP) diagrams are derived. The measurement of enthalpies released by quench-induced precipitation as a function of the cooling rate also enables predictions of the quench sensitivities of Al alloys using physically-based models. Various alloys are compared, and general aspects of quench-induced precipitation in Al alloys are derived.
