Increasing Aging Temperature Research Articles

The effect of aging temperature and aging duration on the dry sliding wear behavior of Ti6Al4V alloy

In this study, Ti6Al4V (Grade 5) alloys were first dissoluted at 850?C for 120 min and then were aged at 250, 350, 450, 550, 650, and 750?C, respectively. After each aging duration (by looking at hardness ratios aged between 9 to 54 hours), the hardness of the samples was measured. Depending on the aging temperature and time increase, hardness increased upon the formation of ?' phases. After the formation of ?' phases, the hardness started to decrease. The highest hardness value was measured in the sample aged at 450?C for 24 hours. The wear behavior of the untreated and the aged samples was investigated through a detailed pin-on-disc test. The effect of the aging temperature on the volume loss, the specific wear rate, and the coefficient of friction were examined. Metallographic analyses were performed before and after the wear tests. Both abrasive and adhesive wear formations were observed on the FESEM-EDS images of the worn surfaces. When the results were evaluated, it was observed that the highest hardness and good wear behavior were obtained for the samples aged at 450?C for 24 hours.

Characterization and predictive modeling of thermally aged glass fiber reinforced plastic composites

Glass fiber reinforced plastics (GFRP) are exposed to thermal aging in their widespread aerospace applications. Evaluating the effect of mechanical properties due to thermal aging has remained a challenge. An experimental investigation to characterize the thermal aging effects of glass fiber epoxy composites as well as the development of a predictive modeling is presented here. Tensile test samples have been thermally aged at 50°C, 100°C, 150°C and 200°C for 30 mins, 60 mins, 90 mins and 120 mins. At higher temperatures, the samples have shown a gradually increasing brown color while emitting a burning smell. The tensile test shows that the UTS value decreases as the thermal aging temperature increases. The predictive model has been prepared by combining image processing, regression analysis and two cascaded artificial neural networks (ANNs). The model reads the photographic image of the sample and uses the color change as an identifier. Cascaded ANNs estimate the thermal aging temperature and time from the image processing program. Finally, the ANN’s output is forwarded to the developed regression equation to get the estimated UTS. The predictive model’s estimated UTS shows an average accuracy of 97% when compared to the experimental results.

Effect of aging temperature on microstructure and mechanical properties of laser melted and hot isostatically pressed (CoCrFeMnNi)96(TiAl)4 alloy

In this study, a selectively laser melted (SLM) and hot isostatically pressed (HIPed) high entropy alloy (HEA), (CoCrFeMnNi)96(TiAl)4, was aged at different temperatures to investigate the microstructural evolution and mechanical property development with the aim of identifying the optimum aging condition that can produce the best combination of tensile properties for the alloy. It was found that the SLM-HIPed HEA contains a small density of nano-sized Al2O3 and σ particles. Upon aging at relatively low temperatures (650 °C and 700 °C), a high density of nano-sized long-range ordered (LRO) L12 domains formed from the matrix. Heusler and B2 particles also started to form from the matrix. With increased aging temperature, both the area fractions and sizes of Heusler, B2 and σ particles increased continuously. Aging at 750 °C gave rise to no LRO L12 domains but γ′ particles while aging at 800 °C led to disappearance of both LRO domains and γ′. The formation of Heusler and B2 precipitates was found to be associated with the diffusion of Al, Ti and Ni while that of σ is linked to the diffusion of Cr. Increased precipitation of Heusler and B2 with increased aging temperature was accompanied by the disappearance of LRO L12 domains, suggesting that the former may have competed with the latter in terms of absorption of Ni, Ti and Al. The samples containing LRO L12 domains and fine precipitates show the highest 0.2% yield strength (YS>610 MPa) and ultimate tensile strength (UTS>960 MPa) while maintaining a high elongation (EL>25%). Those that are free of LRO L12 domains and contain large Heusler, B2 and σ particles show much lower YS (∼490 MPa) and UTS (760–850 MPa) as well as reduced ductility. The results indicate that the formation of LRO L12 domains is crucial for acquisition of enhanced YS in the HEA. In the early stage of plastic deformation, paired dislocations were found to shear through the LRO L12 domains and with increased strains, a number of stacking faults formed with many of them intersecting with each other to form Lomer-Cottrell locks which favoured strain hardening. Dislocations tended to loop around Al2O3, Heusler and σ precipitates, indicating that they can act as effective dislocation motion obstacles.

Investigation of the Thermal Degradation of SBS Polymer in Long-Term Aged Asphalt Binder Using Confocal Laser Scanning Microscopy (CLSM)

Styrene–butadiene–styrene (SBS) polymer is extensively employed for asphalt pavement construction, and its degradation significantly damages the durability of asphalt concrete. However, the effect of aging protocols on the degradation of SBS polymer in asphalt binder has not been thoroughly investigated. In this study, confocal laser scanning microscopy (CLSM) was applied to characterize the change in morphology with SBS polymer degradation. Various aging protocols were considered, including accelerated aging processes in laboratory- and field-aged samples from three highway sections with different in-service periods. Scanned images of the polymer phase in the 2D plane at different depths were processed and further reconstructed in three dimensions. Furthermore, the three-dimensional polymer morphology indices derived from the semi-quantitative analysis of the images were correlated with the rheological indices. The results show that the polymer particles change from a relatively large ellipsoidal shape to a relatively small spherical shape as aging proceeds. The increase in aging temperature appears to accelerate the degradation of the polymer at the same rheological level. The effect of the laboratory aging method on the polymer was more pronounced during the early stages of aging compared to that in the field aging process.

Oxidation of lubricating oil and its influence on the aging behaviors of fluorine rubber

AbstractFluoroelastomer (FKM) has been widely used in aerospace and some particular fields, whose aging is a key problem to influence the service life of the systems. The aging behaviors of FKM in the lubricating oil have been investigated in our previous study. In this work, the influence of intentionally aged or oxidized lubricating oil (A‐O) on the aging process of FKM is reported for the first time comparing with the situation in the fresh oil (F‐O). As the oil medium aged at 200°C for different time, its color, acid number and contact angle with FKM change evidently indicating possible oxidation might occur although the Fourier transform infrared spectrometer (FTIR) has little change. Then, the influence of aged oil medium on the aging behaviors of FKM was further examined. Compared with F‐O, the aging process of FKM in A‐O was significantly accelerated as evidenced by FTIR, tensile strength, mass change, DMA, and macroscopic observation. With the increase of aging temperature from 150 to 200°C, the contrast between A‐O and F‐O conditions become more prominent. Specifically, at 200°C, the crosslinking density and tensile strength of FKM in A‐O decreased by 2.2 × 10−4 mol/cm3 and 2.5 MPa compared to that in F‐O, and the mass change reached to 3.8%, which might be due to the higher amount of oil medium by diffusion into the FKM matrix.

Effect of thermo-oxidative aging on the Payne effect and hysteresis loss of carbon-black filled rubber vulcanizates

In the tire industry, the Payne effect and hysteresis loss of carbon-black (CB) filled rubber vulcanizates are the most concerning issues. CB filled rubber vulcanizates are susceptible to thermo-oxidative aging in the applications. In this paper, the effects of thermo-oxidative aging are investigated from experimental and theoretical aspects. The specimens are subjected to thermo-oxidative aging at 80, 100 and 120 °C for various periods of time ranging from 1 to 6 days and then the dynamic mechanical tests are conducted. The results show that both the storage modulus and the loss modulus increase with increasing aging time. The hysteresis loss of the material shows an increasing tendency with the increase of dynamic strain amplitude, aging time and aging temperature. The Kraus model is used to describe the Payne effect and a viscoelastic model consisting of dynamic strain amplitude and loss modulus is used to calculate the energy dissipation.

Exploring the improvement of strength and cryogenic impact toughness in hot-rolled high Mn austenitic steel for cryogenic application

In general, there is a steep decrease in cryogenic (−196 °C) impact absorbed energy of high Mn austenitic steels after aging at 600–800 °C, which is also the temperature range of aging precipitation. Thus, the precipitation hardening is hardly used in hot-rolled high Mn austenitic steel for cryogenic application and its effect on cryogenic impact toughness is also not understood up to now. In the present work, A high Mn austenitic steel alloyed with Al and V was designed, and the effect of aging temperature on the evolution of microstructure and mechanical properties was investigated by means of electron backscattered diffraction, transmission electron microscopy and X-ray diffraction. The grain size is nearly not affected by aging temperature, exhibiting similar grain size of 6.7–8.1 μm, but the volume fraction and size of precipitated particles greatly depend on aging temperature. The average particle size slightly increases from 5.6 to 6.7 nm with increasing aging temperature from 550 to 650 °C, whereas the precipitated particles are greatly coarsened at 700 °C and the average particle size reaches 16.3 nm. These fine particles can provide a sufficient precipitation hardening of about 200 MPa, leading to a high yield strength of 587 MPa. Meanwhile, this strong precipitation hardening only slight lowers cryogenic impact absorbed energy from 132 to 97 J, also implying that the above-mentioned aging brittle effect should be suppressed or very weak.

Influence Mechanism of Ageing Parameters of Cu-Cr-Zr Alloy on Its Structure and Properties.

The Cu-1.0% Cr-0.1% Zr alloy in a solid solution state was investigated by ageing treatments at different temperatures and holding times. The structure and performance were characterized and tested by using X-ray diffraction (XRD), a transmission electron microscope (TEM), a universal material testing machine, and an eddy conductivity detector. The influence laws of ageing temperature and the holding time on the structures and properties of the Cu-Cr-Zr alloy were analyzed. Results demonstrated that, with the increase in ageing temperature and holding time, the percentage and size of the Cr precipitated phase increased, and the dislocation density decreased. The tensile strength first increased to the peak value and then decreased. The electrical conductivity increased and the amplitude decreased. The tensile strength of the alloy reached the peak (359 ± 2 MPa) after ageing at 450 °C for 60 min, and the electrical conductivity was 91.9 ± 0.7% IACS. In addition, in the ageing precipitation process, the chromium precipitated phase had face-centered cubic structure (FCC) and body-centered cubic structure (BCC) structures, and the FCC Cr phase can be transformed into a BCC Cr phase. FCC Cr, BCC Cr, and Cu3Zr precipitation phases maintained different orientation relationships with the Cu substrate.

Influence of aging temperature on the properties of Cu/(SAC0307 powder +Zn-particles)/Al joints ultrasonic-assisted soldered at low temperature

Purpose This study aims to evaluate the effect of thermal aging temperature on the properties of Cu/Al joints. Design/methodology/approach A new method in which 1 µm Zn-particles and SAC0307 with a particle size of 25–38 µm were mixed to fill the joint and successfully achieved the micro-joining of Cu/Al under ultrasonic-assisted at 200°C, and then, the effect of aging temperature on the properties of Cu/Al joints at different aging times was researched. Findings The results showed that the Cu interface intermetallic compounds (IMCs) had the same composition and had two layers with Cu5Zn8 near the Cu substrate and CuZn5 near the solder. As the aging time increased, CuZn5 gradually transformed to Cu5Zn8, and the thickness of the CuZn5 layer gradually decreased until CuZn5 disappeared completely. There was a Sn–Zn solid solution at the Al interface, and the composition of the Al interface of the Cu/Al joints did not change with changing temperature. The IMC thickness at the Cu interface of the joints continued to increase, and the shear strength of the Cu/Al joints decreased with increasing aging temperature and time. Compared with the as-received samples, the IMC thickness of the Cu interface of joints increased by 371.8% and the shear strength of the Cu/Al joints was reduced by 83.2% when the joints were aged at 150°C for 24 h. With an increase in aging temperature, the fracture mode of the Cu/Al joints changed from being between solder balls and Zn particles to between Zn particles. Originality/value With increasing aging temperature, the shear strengths of the Cu/SACZ/Al joints decreased at the same aging time, the shear strength of Cu/SACZ/Al joints at 150°C for 24h decreased by 83.2% compared with that of the as-received joints.

High-strength and energetic Al2Ti6Zr2Nb3Ta3 high entropy alloy containing a cuboidal BCC/B2 coherent microstructure

The present work developed a novel high-strength and energetic Al 2 Ti 6 Zr 2 Nb 3 Ta 3 high entropy alloy (HEA) containing a BCC/B2 coherent microstructure. The microstructural evolution of BCC/B2 with both the aging temperature (873 ~ 1073 K) and aging time (up to 200 h) was investigated, from which it was found that the cuboidal BCC nanoparticles are coherently-precipitated into the B2 matrix in 873 K-aged state due to a moderate lattice misfit ( ε ~ - 0.76%). The increase of aging temperature could destroy the BCC/B2 coherency and accelerate the formation of brittle Zr 5 Al 3 phase. Especially, the BCC/B2 microstructure exhibits an excellent thermal stability, as evidenced by the fact that these cuboidal BCC nanoprecipitates were not coarsened obviously at 873 K with the particle size from r ~ 10 nm in 24 h-aged state to r ~ 20 nm in 200 h-aged state. This alloy possesses prominent mechanical properties with high yield strength at both room temperature ( σ YS = 1193 MPa) and elevated temperatures (1060 MPa at 873 K and 106 MPa at 1273 K), where the high strength was discussed in light of the precipitation strengthening mechanism. Importantly, the current alloy has an ultrahigh combustion calorific capacity with a value of 10240 J·g -1 , showing a great potential to be used as novel high-performance energetic structural materials. • A high-strength and energetic HEA was developed with the cluster formula approach. • High-strength of alloy was realized by forming a BCC/B2 coherent microstructure. • The BCC/B2 coherent microstructure exhibits a higher thermal stability at 873 K. • The alloy has an ultrahigh combustion calorific value of 10240 J·g -1 .

Microstructure and damping property of Mn-Cu damping alloy by induction brazing and different heat treating

Mn-Cu damping alloy using in complex structural applications often experiences different thermal cycles, so the changes in the microstructure and damping properties of Mn-Cu damping alloys become a focus of attention. In this study, high frequency induction heating technique was used to prepare three-layer Mn-Cu damping structure. The microstructure and damping properties of the composite structure under different heat treatment processes and different heat treatment sequences were analyzed. The experimental results show that the composite Mn-Cu damping structure has good bonding interface and higher shear strength. After solid solution + brazing + aging, the Mn-Cu damping alloy has excellent damping properties for the formation of fine twins and about 10 μm brazing layer. In addition, with the increase of aging temperature and aging time, the quantity of twins becomes less, and α-Mn forms, which leads to the decrease of damping property. The interface between diffusion layer and brazing layer contributes to the improvement of damping properties. The specimen has the best damping property and thermal stability with the process of 900 ℃ × 1 h solid solution + brazing + 435 ℃ × 8 h aging treatment.

Comparison of discontinuous precipitation behavior of Cu-15Ni-8Sn alloy with and without Co addition

The microstructure evolution, phase interface relationships, and corresponding hardness changes of discontinuous precipitation in Cu-15Ni-8Sn alloy during the aging process were investigated. The samples were isothermally aged for 15 h at 500–700 °C to yield discontinuous precipitates with varying lamellar spacings. The results showed that discontinuous precipitation with a lamellar structure is composed of the α-Cu phase and γ-DO3 phase, which has an incoherence interface and satisfies the K-S orientation relationship. With the increase of aging temperature, the lamellar spacing of the discontinuous precipitation increases, the length of lamellar shortens, and the lamellar nature weakens. Simultaneously, the discontinuous coarsening reaction is accelerated. The addition of the trace Co element can inhibit the formation of discontinuous precipitation and discontinuous coarsening phase. Co enrichment was found in the γ-DO3 phase, which can alter the lamellar spacing and then affect the hardness of the Cu-15Ni-0.5Co alloy. In addition, the hardness of discontinuous precipitation in the Cu-15Ni-8Sn- (0.5Co) alloy is negatively correlated with the lamellar spacing and can follow the Hall-Petch type relation.

Destabilization and Ion Conductivity of Yttria-Stabilized Zirconia for Solid Oxide Electrolyte by Thermal Aging.

The degradation behavior of yttria-stabilized zirconia by thermal aging was investigated in terms of phase transformation, local atomic structure, and electrical conductivity. The average grain size of 8YSZ was increased from 20.83 μm to 25.81 μm with increasing aging temperature. All 8YSZ samples degraded at different temperatures had a predominantly cubic structure. The (400) peak of 8YSZ deteriorated at 1300 and 1400 °C shifted to a high angle, and the peak of tetragonal was not indexed. For 8YSZ degraded at 1500 °C, the (400) peak shifted to a lower angle, and the peak of tetragonal was identified. Analysis of the local microstructure of aged 8YSZ using extended X-ray absorption fine structure showed that the intensity of the Zr-O peak gradually increased and that the intensity of the peak of cationic Zr decreased as the aging temperature increased. The changes in the peaks indicate that the oxygen vacancies were reduced and Y3+ ions escaped from the lattice, leading to the destabilization of 8YSZ. The activation energies of 8YSZ at 1300 °C and 1400 °C were derived to be 0.86 and 0.87 eV, respectively, and the activation energy of 8YSZ at 1500 °C increased significantly to 0.92 eV. With the thermal deterioration of 8YSZ, the cation (Y3+) escaped from the lattice and the number of oxygen vacancies decreased, resulting in the formation of a tetragonal structure and high activation energy at 1500 °C.

Microstructural evolution and mechanical properties of a novel biomedical Ti–6Zr–4Fe alloy during solution and aging treatment

Microstructural evolution and its effect on microhardness and Young's modulus of Ti–6Zr–4Fe alloy solution and aging treated at different temperatures were studied. The α phase transformed into β phase completely at 860 °C, meanwhile, the athermal ω phase was found at 860 °C and it resulted in a higher Young's modulus. The ω phase content increased from 250 °C to 400 °C, and the content decreased with further increase of aging temperature, there were only α phase and β phase at 600 °C. The phase transformation sequence was β → ω + β → ω + α + β → α + β during aging treatment. The microhardness increased from 315 HV to 492 HV due to the element solution strengthening and phase transformation strengthening. The peak microhardness of Ti–6Zr–4Fe alloy aged at 400 °C reached 652 HV. The formation of ω phase resulted in the increase of microhardness and Young's modulus in Ti–6Zr–4Fe alloy.

Pd/BEA hydrocarbon traps: Effect of hydrothermal aging on trapping properties and Pd speciation

Interest in Pd/zeolites as automobile exhaust catalysts has driven research focused on understanding the chemical environment of Pd active centers. Here, we studied the effects of hydrothermal deactivation on a Pd/BEA hydrocarbon trap. Hydrothermal aging (HTA) led to decreased ethylene storage capacity and oxidation activity. Characterization by x-ray absorption spectroscopy (XAS) and NOx adsorption indicated that for lower Si/Al ratio samples, the amount of ion exchanged Pd increased after HTA. Temperature programmed desorption of NOx after NO exposure revealed two desorption peaks, with a high temperature peak that increased in area with increased aging temperature. Based on infrared spectroscopy, XAS and reactor results, the high temperature desorption peak is consistent with NO stored on Pd+. The Pd+ formed during NO adsorption, existing originally as [Pd(OH)]+. This species was less active in ethylene storage and oxidation than the original Pd2+ species. [Pd(OH)]+ stored NOx to a higher temperature than Pd2+.

Thermal aging effects on the properties of the Cu/(SAC0307 powder + Zn-particles)/Cu joint ultrasonic-assisted soldered at low-temperature

PurposeThis study aims to evaluate the effect of thermal aging temperature on the properties of Cu/Cu joints.Design/methodology/approachA new method that 1 um Zn-particles and Sn-0.3Ag-0.7Cu (SAC0307) with a particle size of 25–38 µm were mixed to fill the joint and successfully achieved the micro-joining of Cu/Cu under ultrasonic-assisted at low-temperature, and then the effect of thermal aging temperature on the properties of Cu/Cu joints was researched.FindingsThe composition of the intermetallic compounds (IMCs) on the upper and lower interfaces of Cu/SACZ/Cu joints remained unchanged, which was Cu5Zn8 in aging process, and the thickness of the IMCs on the upper and lower interfaces of the Cu/SACZ/Cu joints increased accordingly. Compared with the as-received joints, the thickness of the upper and lower interfaces IMCs of the soldering aged time for 24 h increased by 404.7% and 505.5% at 150ºC, respectively. The IMCs formation tendency and the IMCs growth rate of the lower interface are larger than those of the upper interface because the soldering seam near the IMCs at the upper and lower interfaces of the as-received joints were mostly white SAC0307 balls black Zn-particles, respectively. The growth activation energy of IMCs in the upper and lower interfaces is about 89.21 and 55.11 kJ/mol, respectively. Under the same aging time, with the increase of the aging temperature, the shear strength of Cu/SACZ/Cu joints did not change significantly at first before 150ºC. When the aging temperature reached 150ºC, the shear strength of the joints decreased significantly; the shear strength of the joints was the smallest at 150ºC for 24 h, which was 39.4% lower than that of the as-received joints because the oxidation degree of Zn particles in the joint with the increase of aging temperature and time.Originality/valueCu/Cu joints were successfully achieved under ultrasonic-assisted at low-temperature.

Precipitation and growth of Laves phase and NbC during aging and its effect on tensile properties of a novel 15Cr–22Ni–1Nb austenitic heat-resistant steel

The microstructure evolution and the mechanical properties of 15Cr–22Ni–1Nb austenitic heat-resistant steel were investigated during the aging up to 24 h at 780 °C, 820 °C and 860 °C. A large amount of Laves phase and nano-sized NbC were precipitated during the aging. The NbC particles exhibit excellent coarsening resistance, and the coarsening rate constant of nano-sized NbC particles is four orders of magnitude smaller than that of Laves phase during the aging at different temperatures. The room temperature tensile strength of the heat-resistant steel after aging at 820 °C for 4 h is highest among different aging treatments. The volume fraction of Laves phase increase with the increase in aging temperature and holding time, resulting in a decrease in the ductility of the heat-resistant steel. Ostwald ripening was observed during the aging for 8 h at different aging temperatures. Consequently, the high temperature ultimate tensile strength of heat-resistant steel after the aging for 8 h is lower than that for 4 h and 24 h. The precipitation strengthening contributed by Laves phase and nano-sized NbC was estimated. The yield strength contributed by submicron Laves phase particles is smaller than that provided by nano-sized NbC particles.

GPB-Ⅱ zone in Si microalloyed Al–Zn–Mg–Cu alloy and its strengthening effect

The aging behavior and the strengthening mechanism of the Si microalloyed Al–Zn–Mg–Cu alloy was investigated by means of microhardness tests, tensile properties tests and transmission electron microscope. It was found that the addition of Si element enhanced the microhardness and strength of Al–Zn–Mg–Cu alloy after aging at 125 °C, 175 °C and 225 °C. The age hardening effect of Al–Zn–Mg–Cu alloy gradually deteriorates with the increase of aging temperature, while the age hardening effect of Si-containing Al–Zn–Mg–Cu alloy at different aging temperature are stable. TEM results shows that the intragranular microstructure of the Si microalloyed alloy contained a fine dispersed, lath-like precipitate. This lath-like precipitation phase significantly improves the strength of the alloy and exhibit thermal stability, it is considered to be the GPB-II zone.

Aging characteristics of rice dried using microwave at 915 MHz frequency

AbstractBackground and ObjectivesRice aging is an intrinsic phenomenon that leads to physicochemical changes in rice kernels. The goal of this study is to determine the physicochemical properties of rice dried using a 915 MHz microwave and then aged. Two rice cultivars, a medium grain cultivar Titan and long grain hybrid cultivar XL753, with a harvest moisture content of 20% ± 1% (wet basis) were used for the study. The rice samples were treated with two different drying methods, natural air drying as control and microwave heating at 915 MHz frequency followed by tempering and natural air cooling at 25°C and 56% relative humidity (RH). Microwave‐dried samples were treated at specific energies ranging from 360 to 630 kJ/kg of initial wet grain mass (kJ/kg‐grain). Head rice samples were stored for 6 months at 4°C and 25°C representing nonaged and aged samples, respectively. Physicochemical properties of the samples were determined.FindingsAged microwave‐dried rice had significantly higher setback viscosity, cooked rice hardness and gumminess, and significantly lower peak viscosity and solid loss than nonaged rice. The changes in the viscosity profiles of aged microwave‐dried rice were generally similar to the trends recorded for aged control rice. Furthermore, aging significantly increased the water uptake and kernel elongation ratio of microwave‐dried rice cultivar XL753 but had no significant impact on rice cultivar Titan. Statistical models indicate that the solid loss of microwave‐dried rice decreases by 0.083% while the final viscosity, kernel elongation ratio, and hardness increase by 30 cP, 0.014, and 41 g respectively, with every degree Celsius increase in aging temperature (between 4°C and 25°C), when all other variables are kept constant. Also, aged microwave‐dried rice that were treated at 360 and 525 kJ/kg‐grain were practically equivalent in terms of hardness and solid loss.ConclusionsNatural aging of microwave‐dried rice (dried at 915 MHz frequency) led to changes in some physicochemical properties which were generally similar to the aging patterns of the control rice. Microwave specific energy of 525 kJ/kg‐grain is recommended for rice drying because it produces rice with desirable drying and aging properties.Significance and NoveltyThis study provides processing recommendations that can be used to select microwave parameters for rice drying, which will achieve desirable rice properties.

Investigation on heat treatment of large-sized and complex AlSi9Mg aluminum alloy components formed by squeeze casting

AlSi9Mg aluminum alloy flywheel housing components were formed via squeeze casting and T6 heat treatment was applied to the formed components. The influence of solid solution temperature, solid solution time, aging temperature and aging time on the microstructure and mechanical properties of AlSi9Mg aluminum alloy components formed by squeeze casting were investigated. The results showed that T6 heat treatment changed the morphology of the eutectic silicon in the microstructure from long fibrous to short rods and round spheres. The spheroidization of eutectic Si phase was more obvious with an increase of solution temperature, and the eutectic Si phase not dissolved in the matrix became coarse and grew with an extension of solution time. In terms of mechanical properties, the tensile strength and elongation of AlSi9Mg specimens after heat treatment showed an increasing trend with a rise of solution temperature, but the yield strength decreased, while the three mechanical properties of specimens all improved first and then decreased with an increase of solution time, aging temperature and aging time. Comprehensive consideration of three mechanical properties showed that the optimal heat treatment process parameters in this experiment were solution temperature of 540 ℃, solution time of 180 min, aging temperature of 175 ℃ and aging time of 300 min. In addition, β''−Mg2Si strengthening phases and disc-shaped strengthening phases were precipitated during T6 heat treatment, which were also one of the reasons for the improvement of the casting properties.