Effect of heterogeneously distributed pre-existing dispersoids on the recrystallization behavior of a cold-rolled Al-Mn-Fe-Si alloy
It is well known that strong concurrent precipitation, mainly located along grain/subgrain boundaries, results in a coarse and elongated grain structure, and unusual sharp P {011} and/or M {113} texture components during annealing of supersaturated AA3xxx-series alloys. In this study, a supersaturated as-cast Al–Mn–Fe–Si alloy was annealed at three temperature–time paths after cold rolling and their effects on the softening behavior have been analyzed and compared in terms of final grain structure and texture. In particular, material conditions with dispersoids located along grain/sub-grain boundaries were produced prior to annealing. The effects of pre-existing dispersoids as well as dispersoids formed during annealing (concurrent precipitation), both of which are heterogeneously distributed along grain/sub-grain boundaries, on the recrystallization behavior of the deformed material were investigated and compared. The results clearly show that, due to their larger sizes, these pre-existing dispersoids do not significantly increase the strength of the P/M texture components as compared to the dispersoids formed during annealing, even though the former can still affect the grain structure. It can be concluded that sharp P/M textures develop when recrystallization takes place at low temperature where nucleation of other orientations, whether from particle stimulated nucleation (PSN) or other nucleation mechanisms are suppressed by concurrent precipitation.
The effect of heating rate on the softening behaviour of a deformed Al-Mn alloy with strong and weak concurrent precipitation
The interaction between recrystallization and concurrent precipitation is strongly dependent on the heating rate during annealing. In this study, the effects of heating rate on the grain structure, recrystallization texture and resulting mechanical properties upon annealing of a cold-rolled Al-Mn alloy under strong and weak concurrent precipitation conditions, resulting from different homogenization procedures, were investigated. It is clearly shown that increasing the heating rate leads to finer grain size, less elongated grain structure and reduced flow stress for both cases. In the case of strong concurrent precipitation, a sharp P-texture component is obtained after reaystallization, with its intensity decreasing with increasing heating rate. On the other hand, Cube is the major texture component when concurrent precipitation is weak, and its strength increases with increasing heating rate. The different effects brought about by the heating rate on the recrystallization texture of the two cases, which has not been addressed in the literature so far, are further discussed in view of the differences in precipitation behaviour. (C) 2015 Elsevier Inc. All rights reserved.
Essential Oil Profiles of 168 Perilla Cultivars by Head Space Solid Phase Micro-extraction Gas Chromatography Mass Spectrometry
Abstract In order to comprehensively elucidate the chemical biosynthesis in Perillla (commonly used in traditional herbal medicine), an untargeted analysis based on Gas chromatography-Mass spectrometry was done to reveal the metabolites from 168 different species of Perilla, with 73 components were identified. The results based on the 168 samples, which can be classified into five chemotypes, reveals that different genetic background have a significant influence on the metabolic synthesis of Perilla. The results of heat map for the components of different species and the principal component analysis are implying that the Perilla chemotypes are clustered for characteristic compounds. This study, which used optimized solid-phase microextraction conditions to investigate volatile oil composition, expanded our knowledge of metabolic pathways in Perilla. The differences between chemotypes provide a scientific basis for distinguishing between Perilla species, which not only can improve the testing standards for essential oils from Perilla herbs, but also can be beneficial to Perilla breeding.