In this work, the effect of the growth rate (V L ) and cooling rate (T R ), primary dendritic arm spacing ( 1 ) and Al 2 Cu intermetallic phase on the microhardness was investigated during transient horizontal directional solidification of Al-3wt%Cu and Al-8wt%Cu alloys. Microstructural characterization of the investigated alloys was performed using traditional techniques of metallography, optical and SEM microscopy and X-Ray diffraction. The microhardness evolution as a function of the thermal and microstructural parameters (V L , T R , and  1 ) was evaluated using power and Hall-Petch type experimental laws, which were compared with other laws in the literature. In order to examine the effect of the Al 2 Cu intermetallic phase, microhardness measurements were performed in interdendritic regions. Finally, a comparative analysis was performed between the experimental data of this work and theoretical models from the literature that have been proposed to predict primary dendrite arm spacing, which have been tested in numerous works considering upward directional solidification.

No abstract

Resumo:Este texto discute a proibição da maconha no Brasil, iniciando por uma visão histórica do uso do cânhamo desde o Paleolítico até os primeiros livros impressos e as Grandes Navegações. Em seguida, são abordadas as leis penais brasileiras e suas transformações ao longo das condições da Colônia, Reino Unido, Império e República, enfatizando a marca racista que séculos de regime escravocrata deixam no imaginário social. Após a abolição da escravatura e a proclamação da República, concomitantemente à imigração europeia e ao desejo de 'embranquecer' a sociedade brasileira, o racismo passou a se sustentar sobre as bases pseudocientíficas do pensamento Lombrosiano, que chegaram através de autores Positivistas. Finalmente, são reportados os fatos mais marcantes do proibicionismo em relação às drogas e as mudanças no campo legal ao longo dos séculos XX e XXI, relacionando-os ao relevante papel das Marchas da Maconha no Brasil e no mundo. Palavras-chaveMaconha; poder punitivo; História do Brasil; racismo; direito penal Marijuana Prohibition in Brazil and Slavery Historical Roots Abstract:The subject of this paper is marijuana prohibition in Brazil. It begins with an overall view of the use of hemp from the Paleolithic to the early printed books and Great Navigations seafaring. Then, we discuss Brazilian penal law and its changes during Colony, Portuguese United Kingdom, Empire and Republic, pointing out the racist mark on Brazilian social imaginary after centuries of slavery practices. With the abolition of slavery and the proclamation of Republic, while European immigration was stimulated as a way of "whitening" Brazilian society, racism was supported by the pseudoscientific ideas of Lombroso, brought by Positivist thinkers. Finally, recent facts in this field are reported including penal law changes during the XX and XXI centuries pointing out the relevance of National and Global Marijuana March Movement in this process.

In this paper, primary (λ1) and tertiary (λ3) dendritic arm spacings of a ternary Al -7wt.% Si -3 wt.% Cu alloy casting were characterized and correlated with solidification processing variables: growth rates (VL), cooling rates (TC) as well as local solidification times (tSL). Horizontal directional solidification experiments were carried out under transient heat extraction undergoing cooling rates varying from 0.9 o C/s to 22 o C/s to be associated with samples having quite different microstructural length parameters. Techniques of metallography and optical microscopy were applied in order to have λ1 and λ3 measured. The obtained as-cast microstructures consisted of dendritic α-Al, with Si particles in the aluminum-rich matrix as well distributed along the interdendritic regions in the eutectic mixture interlinked with θ (Al2Cu) intermetallic phase developing the microstructure α-Al + θ + Si. The results showed that power laws -1.1, -0 .55 and 0.55 express the variations of both λ1 and λ3 with VL, TC and tSL, respectively, for investigated alloy. A comparative study with the Al -3wt.% Cu alloy from literature was also performed and the results show that the growth law of λ1 as a function of TC is represented, for both the investigated alloys, by the mathematical expression given by λ1 = constant (TC) -0.55 . thermal parameters during transient horizontal direction solidification of Al -7 wt.% Si -3 wt.% Cu alloy.

An experimental study with an A356-AlSiMgFe alloy was developed to evaluate the microhardness performance in the microstructure resulting of an unsteady-state horizontal solidification process. The Al-7wt%Si-0.3wt%Mg-0.15wt%Fe alloy was elaborated and directionally solidified in a water-cooled horizontal solidification device. In order to experimentally determine the cooling and growth rates (V L and T R , respectively), a thermal analysis was also conducted during solidification. Microstructural characterization by optical microscopy, SEM/EDS elemental mapping and microanalysis of the punctual EDS compositions allowed to observe the presence of an Al-rich dendritic phase (Al (α)) with interdendritic phases second composed of an eutectic mixture: Al (α-eutectic) + Si + Al 8 Mg 3 FeSi 6(π) + Mg 2 Si (θ). Furthermore, the dendritic microstructure was characterized by measuring the secondary dendritic spacings (λ 2) along the horizontally solidified ingot. Higher HV values were observed within the eutectic mixture.