Continuous Cast AA Research Articles

Effect of precipitation state on recrystallization texture of continuous cast AA 2037 aluminum alloy

Various states of precipitation were produced by variation of the aging treatments with and without the solution treatment and pre-deformation. The effect of the precipitation state on the recrystallization texture of continuous cast AA 2037 aluminum alloy was investigated in detail. The results show that as the precipitation state changes from the solution-treated state through the peak-aged state to the over-aged state, the strength of the cube texture decreases, whereas the strength of the R texture increases. In the peak-aged and over-aged samples, the pre-deformation prior to aging decreases the strength of the cube texture and increases the strength of the R texture, and the strength of the R component decreases significantly with increasing annealing temperature. The effect of precipitation on recrystallization in directly cold-rolled hot band is different from that in the cold-rolled solution-treated alloy. The coarser precipitates formed during long-time aging of the hot band are responsible for the stronger cube texture and coarser grains.

Effect of precipitation state on texture evolution in cold-rolled continuous cast AA 2037 aluminum alloy

The texture evolution of continuous cast (CC) AA 2037 aluminum alloy during cold rolling was investigated by X-ray diffraction as a function of the precipitation state. The results show that the various precipitates produced during aging reduce the rate of disappearance of the cube + r-cube component, and that the said rate decreases with increasing aging time. At large strains the θ′ and θ precipitates enhance significantly the rate of disappearance of the remainder component, which implies that the shear bands formed in the grains with remainder orientations accelerate the texture development. The state of precipitation has a significantly effect on the distribution of orientation intensities along the β fiber. With increasing aging time, more initial cube-oriented grains are rotated to the C orientation rather than the B orientation, which leads to a more rapid increase in the intensity of the C orientation with increasing rolling reduction.

The Effect of Fe Content on Recrystallization Texture Evolution, Microstructures, and Earing of Cold Rolled Continuous Cast AA5052 Alloy Sheets

Continuous cast AA5052 Al alloys, containing iron contents of 0.120 and 0.466 wt pct, respectively, were cold rolled and annealed at temperatures ranging from 505 K to 755 K (232 °C to 482 °C). The recrystallization textures in the two alloys were analyzed using X-ray diffraction and electron back scatter diffraction, respectively. It was found that higher Fe content promoted the formation of deformation textures and retarded the formation of cube texture in the two alloys. Most cube-oriented grains formed in both these alloys were associated with coarse particles, whereas the P—{011}〈566〉, R—{123}〈634〉, and Goss or randomly oriented grains were often related to particle stringers consisted of fine particles along the rolling direction. It was also found that the volume fraction of each texture component was a Johnson–Mehl–Avrami–Kolmogorov-type function of annealing temperature in the two alloys. The texture evolution rate with the annealing temperature was calculated from this function and used to determine the onset temperature of each recrystallization texture component.

Effect of heating rate on the microstructure, texture and tensile properties of continuous cast AA 5083 aluminum alloy

Continuous cast (CC) AA 5083 aluminum alloy was cold rolled to 70% reduction and then annealed at different temperatures for 1h in an air furnace at a heating rate of 5°C/min and in a salt bath (~75°C/s), respectively. The effect of heating rate on the microstructure, texture and tensile properties of CC AA 5083 aluminum alloy was investigated. In the case of slow anneal the CC AA 5083 aluminum alloy exhibited a coarse elongated grain structure and a weak {114}〈11¯0〉 recrystallization texture, while a fine equiaxed grain structure and weaker cube and {114}〈11¯0〉 textures were observed in the case of rapid anneal. The rapid anneal promoted the recrystallization of CC AA 5083 aluminum alloy. After complete recrystallization, annealing in a salt bath resulted in higher yield strength and slightly higher ultimate tensile strength than annealing in an air furnace. Lüders elongation phenomenon and serration amplitude of CC AA 5083 aluminum alloy were affected by the annealing temperature and heating rate.

Effect of grain shape on the texture evolution during cold rolling of Al–Mg alloys

The hot bands of continuous cast AA 5754 and high-Fe AA 5754 aluminum alloys exhibited elongated grains in the rolling direction after recrystallization annealing. The annealed hot bands were cold rolled to different reductions along the original rolling direction and transverse direction, respectively. The effect of grain shape on texture evolution was investigated by X-ray diffraction. It was found that straight-rolling resulted in a higher rate of disappearance of the r-cube + cube component and a slightly higher rate of formation of the β fiber component than cross-rolling. The elongated grains in the rolling direction were easier to rotate from initial orientations to the β fiber in straight-rolling than in cross-rolling.

Comparison of earing behavior between continuous cast and direct chill cast AA 5182 aluminum alloys during cold rolling and annealing

The evolution of texture and earing during rolling of continuous cast (CC) and direct chill (DC) cast AA 5182 aluminum alloys was investigated. The results showed that the CC alloy possessed a significantly weaker cube texture than the DC alloy after annealing at 454 °C for 3 h. The evolution of texture and earing during rolling was strongly affected by the initial texture. The 45° earing value of the CC alloy increased with increasing rolling reduction, while the 0/90° earing value of the DC alloy decreased. After 45% cold rolling reduction, the deep-drawn cup of the DC alloy exhibited eight ears at 0°, 45° and 90° to the rolling direction. The DC sheet with minimum earing was obtained at about 83% rolling reduction. The evolution of texture and earing during annealing of the CC and DC alloys was compared. An empirical relationship between the earing value and texture volume fractions was established. Minimization of earing could be achieved by balancing the cube, r-cube and β fiber components.

Effect of Precipitates on the Development of P Orientation {011}$$ \left\langle {566} \right\rangle $$ in a Recrystallized Continuous Cast AA 3004 Aluminum Alloy after Cold Rolling

The as-received hot band (2.54-mm thick) of a continuous cast (CC) AA 3004 Al alloy was cold rolled at reductions, ranging from 25 to 90 pct, and subsequently annealed at 510 °C for 4 hours. Some of these specimens had been annealed at 420 °C for 3 hours with a heating rate of 1 °C/min prior to cold rolling. It was found that the sample with the prior heat treatment exhibited a P orientation ({011}\( \left\langle {566} \right\rangle \)) of 28 pct in volume fraction, stronger than that (23 pct) in the sample without the prior heat treatment, after 90 pct cold rolling and final recrystallization. The transmission electron microscopy (TEM) observations revealed that the prior heat treatment generated very densely distributed Al6(Mn,Fe) precipitates, which could pin dislocations and grain boundaries in the alloy. The formation of stronger P texture in the sample with the prior heat treatment revealed that the P texture could also be developed due to dislocations pinned by the existing fine Al6(Mn,Fe) precipitates during recrystallization in the CC Al alloys that contained Mn.

Quantifying the recrystallization of cold rolled AA 3015 aluminum alloy by X-ray diffraction

The recrystallization kinetics of continuous cast (CC) AA 3015 aluminum alloy with and without pre-treatment has been investigated by X-ray diffraction and measurements of hardness. The variation in texture volume fractions with annealing time reflects better the progress of recrystallization. The JMAK exponent and the activation energy for recrystallization derived from texture data are in good agreement with those from hardness data. Monitoring the change of texture volume fractions during annealing is shown to be a feasible method of determining the recrystallization kinetics of aluminum alloys. The recrystallization kinetics and recrystallization texture of CC AA 3015 aluminum alloy are strongly affected by concurrent precipitation. Concurrent precipitation significantly retards the recrystallization of CC AA 3015 aluminum alloy, decreases the JMAK exponent, enhances the activation energy for recrystallization, and results in a strong P recrystallization texture.

Coincidence Doppler broadening study of phase decomposition in a continuous cast AA 2037 Al alloy

AbstractPhase decomposition in hot band of a continuous cast AA 2037 Al alloy was investigated by coincidence Doppler broadening (CDB) of positron annihilation radiation and positron annihilation lifetime spectroscopy (PALS). It was found that there existed V–Cu and V–Cu–Mg complexes in the as‐received hot band at room temperature. At 200°C, positron average lifetime appeared to be a maximum value because of the formation of semi‐coherent precipitates. The shape of the CDB ratio curve was found to be characteristic of Mn, which indicated the formation of V‐Mn complexes or the existence of Mn clusters in the semi‐coherent precipitates. Above 250 °C, coarsening and dissolution of semi‐coherent precipitates resulted in a decrease in lifetime and disappearance of the Mn signal, but the Cu signal increased clearly with increase in annealing temperature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of heating rate on the microstructure and texture of continuous cast AA 3105 aluminum alloy

The hot band of a continuous cast (CC) AA 3105 aluminum alloy was annealed at different temperatures for 6 h in an air furnace with a heating rate of 11 °C/min and annealed at different temperatures for 30 min in a salt bath (∼50 °C/s), respectively. The effect of heating rate on the microstructure and texture of the CC AA 3105 aluminum alloy was investigated. In the case of slow anneal, the coarse elongated recrystallized grains were observed at the temperatures of 482–599 °C. The recrystallization texture was characterized by relatively strong P orientation and 22.5° ND rotated cube orientation. In the case of rapid anneal, the size and shape of recrystallized grains depended on the annealing temperature. As the annealing temperature increased, the size of recrystallized grains decreased and the recrystallized grains became gradually equiaxed. At 599 °C, a fine equiaxed grain structure was obtained. The recrystallization texture consisted of a weak cube texture. Moreover, the fine-grain alloy produced by the rapid anneal exhibited higher tensile strength and elongation than the slow anneal sample that had a larger grain size.

Texture evolution rate in continuous cast AA5052 aluminum alloy during single pass hot rolling

Continuous cast AA5052 Al alloy slab was hot rolled by a single pass with entrance and exit temperatures of 482 °C and 400 °C, respectively. The thickness of the slab was reduced from 21.5 mm to 8.6 mm. The evolution of texture and microstructure during the rolling was investigated by X-ray diffraction, SEM and optical microscopy. It was found that the grain structure changed from equiaxed to elongated in shape in the alloy at a rolling reduction over 38%. With increase in rolling reduction, the β-fiber texture was increased rapidly in the expense of the remainder component, while the rest of the texture components were only changed slightly during the hot rolling. The evolution of different texture components during the hot rolling process was quantified using modified Johnson–Mehl–Avrami–Kolmogorov-type equations. The corresponding evolution rates were also computed from these equations. Among the three main components (copper, brass and S) in β-fiber, the copper component was the strongest, having the fastest evolution rate, and S the weakest, during hot rolling.

Through-thickness texture gradient in continuous cast AA 5052 aluminum alloy sheet

The development of through-thickness texture gradient during continuous cast (CC) processing of AA 5052 aluminum alloy was investigated by X-ray diffraction. The CC slab and the hot bands after each of three rolling passes were obtained from an industrial CC processing operation. The results show that a through-thickness texture gradient exists near the surface after the first pass. The subsurface layer exhibits a very weak texture, while the center layer shows the β fiber rolling texture. After the third pass, a strong β fiber rolling texture is obtained at different through-thickness layers. The roll-gap geometry does not produce any shear deformation at the intermediate layer. After recrystallization annealing, the through-thickness texture gradient still exists in the AA 5052 aluminum alloy sheets. As the measured position moves towards the center from the surface, the cube recrystallization texture strengthens.

Fatigue of continuous cast AA5754 Al alloy sheet

The continuous casting technology is a cost effective way to produce aluminium alloy sheet. As a result, aluminium alloys produced by this technology have great potentials to substitute steel in autobody panel applications. In the present work, fatigue tests were carried out on hot band (in as received and heat treated conditions) of a continuous cast AA 5754 aluminium alloy (4 mm thick) in directions of 0, 45 and 90° relative to the rolling direction. S–N curves of the alloy were measured in these directions. The alloy was produced using a twin belt continuous caster. The heat treatment on the alloy was conducted using both a batch anneal furnace at a slow heating rate (0·01°C s−1) and an induction heater at a fast heating rate (116°C s−1). The effects of heating/cooling rates during heat treatment on the fatigue anisotropy were studied in the alloy. It was found that induction heat treatment at 465°C greatly improved the tensile isotropy and reduced the fatigue anisotropy in this alloy.

Microstructure, texture and mechanical properties of continuous cast AA 5083 aluminium alloy

Continuous cast AA 5083 aluminium alloy hot band with and without prior heat treatment at 510°C for 3 h was cold rolled to a reduction of 70% and annealed at 399°C for 3 h. It was found that the alloy without the prior heat treatment showed a strong {113}〈110〉 texture component after the thermal mechanical treatment, while with the prior heat treatment its recrystallisation texture was almost random. The alloy with the prior heat treatment exhibited a fine equiaxed grain structure after annealing, in contrast to a coarse elongated one in the alloy without the prior heat treatment. The tensile properties and their isotropy of the alloy were greatly improved by the prior heat treatment. The concurrent precipitation effect was likely to be responsible for the formation of the new texture and inferior mechanical properties of the alloy. Precipitates of 20 nm in size were observed interacting with dislocations in this alloy.

Quantitative Analysis of Texture Evolution of Direct Chill Cast and Continuous Cast AA 1100 Aluminum Alloys during Cold Rolling

The hot bands of direct chill cast (DC) and continuous cast (CC) AA 1100 aluminum alloys were annealed at 454°C for 3 hours, and then cold rolled to different reductions. The texture of the cold rolled samples was measured by X-ray diffraction in order to compare the texture evolution of the DC and CC aluminum alloys during rolling. The texture volume fractions were calculated by an improved integration method. Mathematical formulae of the texture volume fractions and rolling true strain were established to simulate rolling texture evolution. The results show that the DC AA 1100 aluminum alloy exhibits a lower formation rate of the β fiber than the CC AA 1100 aluminum alloy.

Effect of precipitation on rolling texture evolution in continuous cast AA 3105 aluminum alloy

The texture evolution of continuous cast (CC) AA 3105 aluminum alloy during cold rolling was investigated by X-ray Bragg diffraction. The influence of the precipitation state on the texture evolution during rolling was determined. The results show that the precipitates in a CC AA 3105 aluminum alloy affect the texture evolution during rolling. As the amount of precipitates increases and the size of precipitates decreases, the rate of disappearance of the cube, r-cube, and remainder components and the rate of formation of the β fiber decrease. The presence of large precipitates in a CC AA 3105 aluminum alloy hardly affects the texture evolution.

Positron annihilation study of hot band of a continuous cast AA 2037 Al alloy after annealing

Hot band of a continuous cast AA 2037 Al alloy was annealed at different temperatures ranging from room temperature to 500℃ for 3h. Vacancy-solute interaction and precipitates in the hot band samples during annealing were investigated by positron annihilation techniques, coincidence Doppler broadening (CDB) of positron annihilation radiation and positron lifetime spectroscopy, and other methods. The experimental results indicated that there existed V-Cu and V-Cu-Mg complexes at room temperature. At 200℃, positron mean lifetime shows a peak value because of the formation of semicoherent particles. The characteristic shape of Mn was observed in the CDB ratio curve, which indicated the formation of V-Mg-Mn complexes or the existence of Mn clusters in the semicoherent particles. Above 250℃, coarsening and dissolution of semicoherent particles resulted in the decrease of mean lifetime and disappearance of the Mn signal, but the Cu signal increased clearly with annealing temperature. After 350℃, the Cu signal tended to saturation, which reflected that the Cu dissolved might agglomerate and cluster with vacancies during cooling the sample to room temperature, while new increase of mean lifetime might be attributed to the formation of incoherent phase, which was verified by DSC curve.

Evolution of recrystallization and recrystallization texture in continuous-cast AA 3015 aluminum alloy

The evolution of recrystallization and recrystallization texture during annealing after cold rolling of a continuous-cast (CC) AA 3015 aluminum alloy with and without pretreatment was investigated in detail. It was found that the preheat treatment prior to cold rolling significantly affected the recrystallization kinetics, the shape and size of recrystallized grains, and the resulting texture of the CC AA 3015 aluminum alloy. In the case of the alloy without pretreatment, annealing at low temperatures resulted in coarse elongated recrystallized grains and a very strong P texture. As the annealing temperature increased, the size of the recrystallized grains dramatically decreased, the recrystallized grains became equiaxed, and the strength of the P texture decreased. The transition behavior could be attributed to the effect of Zener-particle pinning caused by concurrent precipitation. In contrast, the recrystallization texture of the CC AA 3015 aluminum alloy with pretreatment was characterized by a major cube component and a minor R component, and the annealing temperature did not affect the recrystallization texture. Moreover, concurrent precipitation retarded markedly the recrystallization of the CC AA 3015 aluminum alloy, decreased the Johnson-Mehl-Avrami-Kolmogorov (JMAK) exponent from 2.0 to 0.5, and increased the activation energy for recrystallization from 225 to 539 kJ/mol.

Comparison of the texture evolution of direct chill and continuous cast AA5052 hot bands during isothermal annealing

As-received commercial direct chill cast (DC) and continous cast (CC) AA5052 hot bands were isothermally annealed at different temperatures. The variations of electrical resistivity, hardness, microstructure, and texture of these hot bands during annealing were examined. Texture was investigated by X-ray diffraction. The variation in texture volume fractions with annealing time was quantitatively analyzed by the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. The orientation maps of the partially and fully recrystallized samples were characterized by electron backscattered diffraction (EBSD). It was found that electrical resistivity of the CC AA5052 hot band was higher than that of the DC AA5052 hot band. The electrical resistivity of CC AA5052 decreased more significantly than that of DC AA5052 during isothermal annealing. The DC AA5052 hot band was more easily recrystallized than CC AA5052 hot band during annealing. After complete recrystallization, DC AA5052 hot band possessed a stronger cube texture than the CC AA5052 hot band. The texture evolutions of DC and CC AA5052 can be expressed quantitatively by the JMAK equation after the volume fractions of the texture components are calculated by an improved integration method. Annealing temperature had an influence on the n values in the JMAK-type equations. The n values are small at low annealing temperatures.

Effect of hot and cold deformation on the recrystallization texture of continuous cast AA 5052 aluminum alloy

The effect of different relative amounts of hot and cold deformation on the recrystallization texture of a continuous cast AA 5052 aluminum alloy was investigated by X-ray diffraction. The results show that hot deformation promotes the cube and Goss components at the expense of the r-cube and remainder components. The formation of the R component does not appear to be affected by hot and cold deformation.