Influence of static tensile testing on the deformation behavior of Al–4% Cu alloy containing micro- and nanoparticles

At present, aluminum alloys reinforced with nonmetallic particles are of great interest in various fields of science and technology due to their high specific strength, hardness, wear resistance, and other properties. At the same time there is a great interest in the study of processes occurring during plastic deformation of such materials under static tensile loading. Plastic flow of metals occurs through the creation and movement of linear defects (dislocations), in which there is a phenomenon of discontinuous yielding. An introduction of particles into aluminum alloy promotes a considerable increase of stiffness and specific strength of alloys, and the study of the deformation behavior of such alloys is of great interest. The objective of this research is to analyze mechanical properties and the deformation behavior of aluminum alloy with the identification of mechanisms of plastic deformation when introducing solid nonmetallic micro- and nanoparticles into the soft aluminum matrix. An analysis of the microstructure of the obtained alloys shows that the introduction of particles (Al2O3, TiB2, TiC) leads to a reduction of the alloy grain size from 350 to 170 µm while residual porosity does not exceed 2%. Tensile tests performed show that the change in the type and quantity of particles also changes characteristics of discontinuous yielding, thus resulting in an increase of yield strength (from 18 to 40 MPa), reduction of ductility (from 15 to 2%), and moreover a significant increase of tensile strength (from 77 to 130 MPa), as compared to the initial Al–4 wt % Cu alloy

Structure, phase content and mechanical properties of aluminium with hard particles after shock-wave compaction

The possibilities to combine metal and metal oxide powders in various compositions open a broad range of mechanical and thermal behavior. When using in nanostructured components the resulting materials might exhibit even more interesting properties, like product effectiveness, tensile strength, wear resistance, endurance and corrosion resistance. Intermetallics like TiAl could be obtained as TiAlx in a quality similar to that obtained from melting where only eutectic mixture can be produced. Similar effects are possible when compacting nanoceramic powders whereas these can be combined with intermetallics. Currently, it is very difficult to produce wires and special shaped parts from high temperature superconducting materials. The compacting by explosives could solve this problem.The present paper uses explosion compacting of Al nanoparticles to create nanocomposite with increased physico-mechanical properties. Russian civil explosive Uglenit was chosen as high energy material (HEM) for shock-wave compaction. The different schemes and conditions were suggested to run the explosion process. Al nanoparticles as produced by electric wire explosion contain 8-10% of aluminum oxide. That aluminum oxide can serve as strengthening material in the final nanocomposite which may be generated in various compositions by explosive compacting. Further modifications of nanocomposites were obtained when including nanodiamonds into the mixture with aluminum nanoparticles with different percentages. The addition of nanodiamonds results in a substantial strengthening effect

Theoretical and experimental investigations of the process of vibration treatment of liquid metals containing nanoparticles

It is known that the use of external effects, such as acoustic fields (from ultrasonic to low-frequency range), help in breaking down agglomerates, improving particle wettability, providing uniform particle distribution in the melt volume, and reducing the grain size. The fragmentation of growing crystals, de-agglomeration of particles and their mixing in liquid metal under the influence of vibration (with frequencies of 10–100 Hz) are considered in this paper. The major advantage of such a technique in comparison with high-frequency methods (sonic, ultrasonic) is the capability of processing large melt volumes proportional to the wavelength. The mechanisms of the breaking down of particle agglomerates and the mixing of particles under conditions of cavitation and turbulence during the vibration treatment of the melt are considered. Expressions linking the threshold intensity and frequency with the amplitude necessary to activate mechanisms of turbulence and cavitation were obtained. The results of vibration treatment experiments for an aluminum alloy containing diamond nanoparticles are given. This treatment makes it possible to significantly reduce the grain size and to improve the casting homogeneity and thus improve the mechanical properties of the alloy

Structure and deformation characteristics in magnesium alloy ZK51A reinforced with AlN nanoparticles

The aim of this work was to study the influence of nanoparticles of aluminum nitride on the structure and mechanical properties of magnesium alloy. We examine the resulting magnesium alloys. The experiment consisted in the introduction into the melt of magnesium aluminum nitride powder in an amount of 0.75 and 1.5%. Introduction of nanoparticles into the molten metal was carried out by external vibration exposure. Studies were carried out of aluminum nitride powder, comprising X-ray diffraction analysis to study the morphology using electron microscopy. Introduction of nanoparticles in the alloy increases the pore volume space from 5 to 15% and increased average pore size from 8 to 30 µm. It was shown that the presence of the nanoparticles in an amount of 1.5% increases the alloy properties by more than 30% compared with the reference (non-particulate) alloy. We were obtained diagrams such as stress - strain. It was also carried out studies of the structure and X-ray analysis of the alloys obtained

Comorbidades psiquiátricas em adolescentes internados com transtorno de uso de substâncias

Orientador: Prof. Dr. Gustavo Manoel S. DóriaDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências da Saúde, Programa de Pós-Graduação em Saúde da Criança e do Adolescente. Defesa : Curitiba, 25/11/2016Inclui referências: p. 74-88Resumo: O objetivo desse estudo é avaliar as comorbidades psiquiátricas em adolescentes com Transtorno de Uso de Substâncias (TUS) internados na cidade de Curitiba. O abuso de substâncias e a presença de comorbidades psiquiátricas na adolescência, aumenta o comportamento disfuncional do adolescente, o coloca em riscos (evasão escolar, gestações indesejadas, criminalidade, homicídio, suicídio), chegando a ser um problema de saúde pública. O TUS na adolescência se tornou um grande problema social e de saúde. A idade da primeira experimentação tem diminuido e a precocidade do uso aumenta o risco para desenvolver dependência e outros transtornos psiquiátricos. Espera-se que grande parte dos adolescentes dependentes de substâncias apresentem comorbidades psiquiátricas. A versão brasileira do Schedule for Affective Disorders and Schizophrenia for School Aged-Children (K-SADS-PL) foi aplicada a 35 adolescentes do sexo masculino que foram hospitalizados por TUS na cidade de Curitiba. Verificou-se que 92% dos adolescentes tinham alguma comorbidade psiquiátrica. As comorbidades mais frequentemente observadas foram o Transtorno de Conduta (TC) (57,1%), Transtorno de Déficit de Atenção e Hiperatividade (TDAH) (48,6%) e Transtorno opositor desafiante (TOD) (40,0%). A maconha (94,2%) e o crack (40,0%) foram as principais substâncias utilizadas pelos adolescentes. O uso de maconha esteve mais frequentemente associada a efeitos negativos sobre o comportamento e vida dos adolescentes. É de extrema importância avaliar os fatores que podem prevenir a progressão de um transtorno e/ou comorbidade para diminuir os prejuízos do desenvolvimento do adolescente e o custo gerado para o tratamento tardio. Desta forma, é necessária a implantação de serviços que atendam essa população. Palavras-chave: Transtornos Relacionados ao Uso de Substâncias. Psiquiatria Infantil. Psiquiatria do Adolescente. Transtornos Mentais.Abstract: The aim of this study is to evaluate psychiatric comorbidity in hospitalized adolescents with Substance Use Disorder (SUD) in the city of Curitiba. Substance abuse and the presence of psychiatric comorbidities in adolescence increases the dysfunctional behavior, puts him at risk (school dropout, unexpected pregnancies, criminality, homicide, suicide), becoming a public health problem. Substance Use Disorder in adolescence has become an important social and health problem. The age of first experimentation has decreased and the precocity of use increases the risk for dependence and other psychiatric disorders.It is expected that most of the adolescents with substance dependence have psychiatric comorbidities. The Brazilian version of the Schedule for Affective Disorders and Schizophrenia for School Aged-Children (K-SADS-PL) was applied to 35 male adolescents with SUD who were hospitalized in the city of Curitiba. It was found that 92% of adolescents had some psychiatric comorbidity. The most frequent comorbidities among adolescents of this present study were Conduct disorder (CD) (57.1%), Attention deficit hyperactivity disorder (ADHD) (48.6%) and Oppositional defiant disorder (ODD) (40.0%). Marijuana (94.2%) and crack (40.0) were the main substances used by adolescents. The use of marijuana was the most frequently associated with negative effects on the behavior and lives of adolescents. It is very important to assess the factors that can prevent the natural progression of a disorder and/or comorbidity to reduce the impairment of the adolescent development and the cost for late treatment. Thus, the development of services that support this population is needed. Keyword: Substance-Related Disorders. Child Psychiatry. Adolescent Psychiatry. Mental Disorders

Influence the carbon nanotubes on the structure and mechanical properties of aluminum-based metal matrix composites

It is known that metal matrix composites reinforced with non-metallic inclusions are of great interest in various fields of technology owing to a good combination strength to weight ratio. Carbon nanotubes (CNTs) are expected to be ideal reinforcements for composite materials due to their high modulus and low density. In this paper metal matrix composites were obtained through hot pressing of powder mixtures Al-1% and 5% carbon nanotubes at different isothermal time. Hardness and density of materials went up with an increase in the isothermal holding time. However, the hardness of composites decreases with an increase the nanotubes content in the material