Thermo-mechanical processing and the shape memory effect in an Fe–Mn–Si-based shape memory alloy

The effect of cold rolling and annealing on the shape memory effect (SME) in an Fe–Mn–Si-based alloy has been studied. It has been found
that the SME in these alloys can be significantly increased by the appropriate thermo-mechanical processing (TMP). The optimum conditions
were found to be 15% cold rolling followed by annealing at 800 ◦C for 15 min. This produced a total strain recovery of 4.5%. TEM showed that
this processing schedule produces a microstructure of evenly spaced, and well defined stacking faults throughout the parent phase. It is shown for
the first time that samples processed in this way produce a larger fraction of martensite compared to samples in the as-austenitized condition. It
is concluded that the stacking faults induced by TMP act as nucleation sites for martensite formation during deformation. The SME is improved
primarily as a result of the increased amount of martensite that is formed in this condition.

Effect of NbC and TiC precipitation on shape memory in an iron-based alloy

This paper examines the effects of TiC and NbC precipitation and prior cold rolling on the shape memory behaviour of an iron-based alloy. A precipitate-free alloy was used as a reference to investigate the relative contributions of prior-deformation and precipitation on shape memory. Heat treatment of the Nb- and Ti-containing alloys at 700 °C and 800 °C resulted in carbide precipitates between 120 nm and 220 nm in diameter. Bend testing of these samples showed a marginal increase in shape memory compared to the precipitate-free alloy. Under these conditions TiC precipitation exhibited slightly better shape memory than for NbC. However, this small increase was over-shadowed by the marked increase in shape memory that can be produced by subjecting the alloys to cold rolling followed by recovery annealing. When processed in this way, fine carbides are formed in the Ti- and Nb-containing alloys during the heat treatment. For particles >25 nm in diameter the shape memory is unaffected, but, it was found that small <5 nm particles have a detrimental effect on shape memory due to pinning of the martensite plates, thereby inhibiting their reversion to austenite. The optimum shape memory was observed in the precipitate-free alloy after cold rolling and recovery annealing.

Effect of second-phase particles on shape memory in Fe-Mn-Si-based alloys

The shape memory behaviour of two Fe–Mn–Si-based alloys has been investigated. One alloy was a reference alloy, and the other alloy was
similar in composition except that it contained 0.55 wt% Ti. Following solution treatment and quenching, strip samples were subjected to three types
of treatments; isothermal holding, cold rolling followed by isothermal holding, and hot rolling followed by isothermal holding. These treatments
resulted in the formation of intermetallic precipitates in the Ti-containing alloy, while the reference alloy remained precipitate-free. In comparing
the shape memory of the reference and the particle-containing alloy after identical heat treatments, it was found that the formation of precipitates
had a beneficial effect on the shape memory in all cases. In general, the larger precipitates caused a larger increase in the shape memory. The effect
of particle size on shape memory has been analysed using the current data and published results for a range of precipitate types.

Effects of deformation-induced heating on bond strength of rolled metal multilayer

The bond strength of various metal multilayers produced by cold rolling of metal foils with different thermal conductivity was investigated. Results indicated that under the same conditions of deformation and surface preparation, the metallic multilayer system with low thermal conductivity exhibited relative high bond strength while high thermal conductivity metal system may fail to be roll-bonded together. The relationship between the deformation-induced localized heating and the bond strength were discussed. The deformation-induced localized heating in the low thermal conductivity metal multilayer systems may provide opportunities for achieving a successful accumulative roll bonding or a “cold roll/heat treatment/cold roll” process to synthesize metallic multilayer materials.

Local laser heat treatment in dual-phase steels

This research deals with processes leading to local strengthening effects in hot-rolled dual-phase (DP) steels. For this purpose, a method was investigated to achieve local strengthening, namely, local laser heat treatment (LHT). DP sheet steels were globally and homogenously deformed with different degrees of prestrains by cold rolling and subsequently locally heat treated by laser. Following this treatment with selected parameters, the microstructure of the surface and cross section of the heat-treated area as well as the mechanical properties were evaluated by light optical microscopy (LOM), scanning electron microscopy (SEM), as well as transmission electron microscopy (TEM), hardness measurement, and tensile testing. It can be stated that with partial heat treatment, local high strengthening can be produced. At lower heat treating temperatures, this effect could be attributed to bake hardening (BH). Increasing the prestrain as well as temperature results in improving the local properties. With increased heat treating temperature, the initial microstructure near the surface is affected. Partial strengthening of DP steels by laser can open up new fields of application for locally using the strengthening effect to only influence relevant areas of interest, thus providing the potential for saving energy and designed the component's behavior.

Effect of grain size on corrosion of high purity aluminium

A complete understanding of how grain refinement, grain size, and processing affect the corrosion resistance of different alloys has not yet been fully developed. Determining a definitive 'grain size-corrosion resistance' relationship, if one exists, is inherently complex as the processing needed to achieve grain refinement also imparts other changes to the microstructure (such as texture, internal stress, and impurity segregation). This work evaluates how variation in grain size and processing impact the corrosion resistance of high purity aluminium. Aluminium samples with a range of grain sizes, from ∼100 μm to ∼2000 μm, were produced using different processing routes, including cold rolling, cryo rolling, equal channel angular pressing, and surface mechanical attrition treatment. Evaluation of all the samples studied revealed a tendency for corrosion rate to decrease as grain size decreases. This suggests that a Hall-Petch type relationship may exist for corrosion rate and grain size. This phenomenon, discussed in the context of grain refinement and processing, reveals several interesting and fundamental relationships.

Effect of roller leveling on the bending behaviour of aged steel strip

The common grades of steel used in roll forming are: hot rolled carbon steel, high strength low alloy and recovery annealed cold rolled sheet. These steels are prone to ageing and are often skin passed and/or roller leveled to eliminate ageing as it can lead to problems in forming. In roll forming, shape defects such as bow, twist and camber are considered to be related to very small plastic strains in the longitudinal direction and hence knowledge of the material properties in the elastic plastic transition range is necessary if the process is to be modelled accurately. Previous studies with aluminium have indicated that skin pass rolling can lead to residual stresses in the strip. In this work, the study was extended to aged carbon steel and to the effect of roller leveling on both aged material and strip that had been given a light cold rolling to simulate a skin pass treatment. The results suggest that roller leveling reduced the magnitude of residual stresses resulting from skin pass rolling.

The significant differences observed between tensile and bending test results, at and near, the elastic plastic transition reinforces the need to consider bending properties when assessing the effect of prior processing on strip for roll forming.

FeNbP in ultra-low carbon Nb-added steel containing high P

Precipitation of FeTiP is reported to occur in Ti-added IF steels containing high P during thermomechanical processing. An ultra-low carbon (ULC) Nb-added steel ingot containing a higher P content (< 0.8 wt-%) was produced via aluminothermic reduction of Fe2O3 followed by double electron beam melting (EBM). FeNbP coarse precipitates were observed in the as-cast microstructure. After soaking at 1050C for 1 h, the plate was hot rolled from 31 mm down to 7 mm in thickness (total reduction of 77%). During cold rolling of these hot bands we observed embrittlement. We believe that this embrittlement can be attributed to the presence of the FeNbP precipitates. Light optical and scanning electron microscopy (SEM/EDS) were used to characterize the microstructure of this ULC steel. (C) 2000 Elsevier B.V. All rights reserved.

Análise da influência dos solutos Zr e Ti sobre as propriedades mecânica, elétrica e de termorresistência de uma liga Al-Cu-Fe-Si destinada a Tx e a Dx de energia elétrica

O contexto energético mundial apresenta um aumento constante do consumo de energia elétrica no último século, desta forma exigindo a pesquisa de novos materiais para a aplicação em cabos e fios condutores de eletricidade. A partir destas demandas por novos materiais, desenvolveu-se uma análise da influência dos solutos zircônio e titânio na modificação de características importantes de uma liga Al-Cu-Fe-Si, destinada a ser o meio condutor de energia elétrica, almejando obter propriedades termorresistentes. Para a realização deste estudo, as ligas foram obtidas por fundição direta em lingoteira metálica em formato “U”, a partir do Al-EC, fixando-se na liga-base os teores de 0,05% Cu, [0,24 a 0,28]% Fe e 0,7% de Si, e em seguida, inserindo-se os teores de 0,26% Zr e 0,26% Ti. O experimento foi dividido em duas etapas, ETAPA A e ETAPA B, respectivamente, com o intuito de se avaliar as características mecânicas, elétricas e estruturais das ligas. Os corpos de prova após laminação a frio (nos diâmetros 2,7; 3,0; 3,8 e 4,0 mm) foram analisados sem tratamento térmico (STT) e com tratamento térmico (CTT): 230 ºC por uma hora, de acordo com o protocolo COPEL, 310 ºC e 390 ºC por uma hora, visando avaliar a ermorresistência em temperaturas mais elevadas, a estabilidade térmica e analisar as microestruturas desenvolvidas em tais tratamentos térmicos (TT). Verificou-se que o Ti tem maior capacidade de refinar o grão em relação ao Zr, que apresenta grãos menos refinados, porém com melhores propriedades físicas e apresentando-se termorresistente.

Preparação e caracterização estrutural, mecânica e anelástica de ligas do sistema Ti-Ta contendo oxigênio intersticial, para uso biomédico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Um estudo sobre o endurecimento, o processamento e propriedades mecânicas de uma liga de alumínio da série 3XXX tipo AA 3104 com adições de zinco

Modificações na composição química e no processamento termomecânico têm sido algumas das várias alternativas estudadas, para melhorar o desempenho de ligas de alumínio tradicionais. Neste trabalho foi modificada a composição de uma liga Al-Mn-Mg do tipo AA 3104, endurecível por deformação, adicionando-se diversos teores de zinco, transformando-a numa liga Al-Mn-Mg(Zn), endurecível por precipitação. O objetivo foi estudar e quantificar os efeitos do zinco sobre o processamento termomecânico e as propriedades mecânicas da liga modificada. Ligas com teores de zinco entre 0,03 a 1,52% foram fundidas e processadas obtendo-se um encruamento semelhante a condição H-19 industrial, denominada rota R. Ligas com teores de zinco entre 1,14 a 2,17% foram fundidas e processadas segundo três diferentes rotas: na rota S, o recozimento da rota R foi substituído por solubilização antes da laminação a frio; nas rotas E3H e E6H, as tiras laminadas a frio foram envelhecidas em dois estágios: 121°C por três horas para as duas rotas, mais três horas para a rota E3H e seis para a rota EH a 163°. A tensão de escoamento (SIGMA IND E) e a resistência à tração (SIGMA IND T) para a rota R aumentaram da ordem de 18% e 19% respectivamente, com o aumento do teor de zinco, enquanto o alongamento (E) permaneceu em torno de 4,5%. As propriedades mecânicas (SIGMA IND E SIGMA T E ) AUMENTARAM EM TORNO DE 25%, 31% E 27%, respectivamente, para a rota S. Considerando concentrações aproximadamente iguais de zinco, não foram verificadas diferenças significativas para (SIGMA E SIGMA T), entre as rotas R E S, no entanto, a rota S apresentou alongamento médio maior que a rota R da ordem 44%. Os menores valores de (SIGMA IND E SIGMA IND T) e os maiores valores de E foram obtidos para a rota E6H.

Determinação por meio de planejamento de experimentos da influência do lixamento nas medidas de dureza com durômetro portátil de método UCI

The hardness has an important role in quality control, in research studies and metallurgical and mechanical specification, selection and comparison of various materials. This property is of extreme importance in the oil industry because it is a determining factor to ascertain the safety of the material used in pressure vessels and pipelines. Due to the inability to stop the equipment while checking the hardness, the hardness testers are widely used portable method UCI, its great advantage is the fact that an essay fast, simple realization and not be considered a non-destructive testing with a good relationship money. The objective is to determine if there is significant difference in hardness measurements between 80 and 1200 sandpaper using a portable hardness tester UCI method, the material applied in gas storage spheres composition ASTM 516 Gr 70. After determining the number of homogeneity, we performed the hardness profile to isolate the major factors influencing the hardness part: cold rolling and segregation of impurities. Factors Cooling and sanding were analyzed using the method of design of experiments (DOE), in which it was demonstrated that neither variables nor their interactions, has significant influence on the hardness measurements by portable MIC 10. This fact will lead to reduction in time and cost for surface preparation

Influência do tratamento térmico de homogeneização na microestrutura de um aço utilizado na fabricação de cilindros de laminação para trabalho a frio

Pós-graduação em Engenharia Mecânica - FEG

Impactos causados por vibrações mecânicas em chapas de alumínio no processo de laminação a frio

This paper purpose is to analyze one of the main problems faced by cold rolling industry of the current time, the mechanical vibration. Factors such as strips with high velocity in order to increase the productivity and thickness becoming thinner and thinner cause the vibrations to be present at all times during rolling. These market requirements also drive the industry for technology development and thus bring the challenges that the operation of a new modern equipment and more powerful. The initial purpose is to analyze the forces that cause vibration in a rolling mill type four high with two stands, where is desirable to identify the origins of these vibrational forces to make possible dismiss them or at least control its intensity, in order to prevent damage in the rolling mill and ensure product quality to the customer. For it, will be used instruments to record and store the vibrations that occur during the lamination process. With this data will be able to analyze the characteristics of the vibrations and act at your elimination. At the end of the work is expected to demonstrate how important the critical view of the engineer in the analysis of graphics combined with the calculations of the natural vibration frequency and engagement of key parts of the laminator. With these two tools at hand, will be possible to increase the productivity of the rolling mill and act preventively in maintenance, thereby reducing your downtime and increasing its performance and efficiency