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The influence of pre-strain on the tension and creep behavior of Al-Mn-Mg containing nano-sized TiC particles at elevated temperatures was investigated. Introduction of TiC nano-particles and the application of pre-strain significantly increase the strength at the ambient temperature and at 473 K, even though the strengthening effect diminishes at 573 K due to the more activated dislocation climb. Small pre-strain (von Mises strain of 0.2) could increase the yield strength at 573 K from 72 MPa to 96 MPa. Larger pre-strain promotes the precipitation during hot deformation at 573 K, and concurrent precipitation suppresses work softening by the pinning effect, leading to a significantly enhanced ductility and creep rupture life. [ABSTRACT FROM AUTHOR]

The precipitation kinetics during non-isothermal annealing of an Al-Mn alloy (AA3003) rolled over a large strain range ( ε = 0–2) has been investigated. Precipitation strengthening can overtake recovery softening when prestrained alloy was annealed below 573 K. The precipitate size distributions were similar in undeformed and prestrained alloys annealed at low temperature (673 K). We developed a coupled deformation-recovery-precipitation model for nucleation kinetics of heterogeneous precipitation. Strain-induced dislocations significantly promote nucleation at small and moderate strains while nucleation rate on sub-boundaries of higher misorientation increases by orders of magnitude with strain, and becomes dominant at large strains. [ABSTRACT FROM AUTHOR]

The influence of concurrent precipitation on recrystallization is analyzed by comparing the nucleation and growth behavior of P ({011} 〈566〉), Cube ({001} 〈100〉), and 20 deg ND-rotated Cube ({001} 〈310〉, NDcube)-oriented grains in Al- xMn-Fe-Si ( x = 0, 0.4, 1.0 wt pct) alloys. The number densities of recrystallized grains in alloys annealed at various temperatures clearly demonstrate that concurrent precipitation significantly reduces the nucleation density of recrystallization. However, this effect varies strongly with grain orientation, and the P orientation is affected less than other orientations, in particular the Cube orientation. The number fraction of P-oriented grains can increase ten times as the effect of concurrent precipitation enhances. The P- and NDcube-oriented grains grow faster than Cube grains when strong concurrent precipitation occurs. However, on the other hand, when precipitation is limited or completely absent, P grains grow more slowly than Cube (and NDcube) grains. Micro-segregation enhances the effect of concurrent precipitation, indicating that the effect is closely related to heterogeneous distribution of precipitation. [ABSTRACT FROM AUTHOR]

We consider the elastic effect of clusters and propose a size misfit strengthening model. Our approach is similar to solute strengthening, where the size misfit of clusters is assumed to be the sum of elementary atomic misfits. The proposed model is compared to the coherency strengthening model, and the results indicate that our model is applicable to clusters ∼<1nm in diameter. The prediction of the model is reasonably consistent with the reported experiments of aluminium alloys. [Copyright &y& Elsevier]

The influence of dispersoids on tensile deformation behaviour has been studied by comparison of aluminium alloys containing different dispersoid densities. It was found that a fine dispersion of non-shearable particles led to an increased work hardening at the initial plastic deformation, but the effect was opposite at higher strains. The reason has been attributed to the generation of geometrically necessary dislocations (GNDs). A new model has been proposed for the evolution of GNDs based on a balance of storage and dynamic recovery of GNDs. The model predicts a rapid saturation of GNDs and a reduced work hardening at small strains, consistent with the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: Solution hardening of Al–Si alloys at room temperature was investigated by tensile tests of several aluminum alloys containing various amounts of Si in solution but fabricated from the same commercially pure base material. It is found that Si has a weak strengthening effect but a significant impact on the work hardening. The strengthening was found to be very sensitive to water quenching, which enhances the solute strengthening. Despite the low strengthening effect, the Portevin–Le Chatelier effect was clearly observed during the tension of an alloy containing 0.4at% Si, suggesting the occurrence of dynamic strain ageing due to surprisingly low levels of Si in solid solution. [Copyright &y& Elsevier]

In this work, the effects of cooling rate and the addition of TiC nanoparticles on the as-cast microstructure, precipitation behavior during subsequent heat treatments and mechanical properties were investigated. The grain size (GS), secondary dendritic arm spacing (SDAS) and primary particle size are the function of cooling rate v , following a similar power law, D = Av -n (D is the size of grains/SDAS/primary particles, A and n are constants). The TiC addition reduced the A value for grain size and primary particles but increased A for SDAS. The addition of TiC nanoparticles promoted the coarsening of secondary dendritic arms, leading to the reduced microsegregation and smaller interdendritic/intergranular secondary phase (Al 2 Cu). Consequently, the precipitation of the θ′ phase during ageing treatment was promoted, and the precipitates were refined and more dispersive, contributing to the increased tensile strength. The improved ductility was ascribed to the combination of reduced secondary phases and micropores. With the combination of high cooling rate and TiC addition (cooling rate: 93 °C/s; 0.5% TiC addition), the yield strength, ultimate tensile strength and uniform elongation of the Al–5Cu cast alloy were simultaneously improved, and reached those of Al–5Cu rolled sheet. [ABSTRACT FROM AUTHOR]

The coupled effect of strain-induced precipitation and stabilized substructure on the elevated-temperature strength of an Al–Mn–Si alloy and its thermal stability have been investigated. Prestrain significantly promotes the nucleation of nano-sized dispersoids, and strain-induced precipitation suppresses recrystallization, stabilizing substructure at elevated temperatures. Compared with the dispersoids formed during the heat treatment of as-cast alloy, substructure does not increase the coarsening rate of strain-induced precipitates. The strain-induced precipitation and stabilized substructure profoundly strengthen the aluminum alloy at the elevated temperature (300 °C). [ABSTRACT FROM AUTHOR]