Neural network modelling of hot deformation of austenite

The hot deformation behaviour of austenite in steels is a complicated process which depends on chemical composition, microstructure, temperature and strain rate. While many models have been developed to represent the flow stress as a function of these variables, it is not yet possible to predict the behaviour for a new alloy. Linear regression techniques are not capable of representing the data, however, neural networks are capable of modelling highly non-linear data. A neural network model was developed in this work using a large database of various steels. The model allows the calculation of error bars that depend upon the position of a prediction in the input space and the level of perceived noise in the data. The validity of the model was evaluated by comparing its outputs against those of the six carbon-manganese steels with different compositions

Measurement of residual stresses in dissimilar friction stir-welded aluminium and copper plates using the contour method

The longitudinal residual stresses in the friction stir-welded plates of 5A06 aluminium and pure copper were determined using the contour method. The results revealed the presence of high tensile and compressive residual stresses on the aluminium and copper sides, respectively. The residual stresses were detected on the weld zone as well as the thermo-mechanically affected zone (TMAZ) of the aluminium plate. In contrast, the compressive residual stresses in the copper plate had a much narrower width along the weld line. Peak tensile stresses up to 240 MPa were found in the TMAZ of the aluminium plate

Diffusion bonding of copper alloy to nickel-based superalloy: effect of heat treatment on the microstructure and mechanical properties of the joints

Successful joining of heat conducting materials, to high-temperature components is of significant importance for heat management in nuclear power plants and liquid propellant launch vehicles. Solid-state processes are considered for joining such dissimilar materials. Diffusion bonding of a copper alloy (C18150) to a Ni-based superalloy (GH4169) was investigated in this work. The bonding trials at 900°C for 60 min under a constant 10 MPa pressure led to formation of sound joints free from intermetallic, pores, voids and discontinuities. Conventional tensile testing led to the failure within the copper alloy and away from the joint. Due to the softening of the copper alloy during the bonding process, the maximum tensile strength of the as-bonded copper alloy was only 48% of its as-received strength. Post-bonding solution treatment at 960°C for 60 min followed by ageing at 450°C for 3.5 h, restored the tensile strength of the copper alloy up to 77%

Fail-Safe Joints between Copper Alloy (C18150) and Nickel-Based Superalloy (GH4169) Made by Transient Liquid Phase (TLP) Bonding and Using Boron-Nickel (BNi-2) Interlayer

Joining heat conducting alloys, such as copper and its alloys, to heat resistant nickel-based superalloys has vast applications in nuclear power plants (including future fusion reactors) and liquid propellant launch vehicles. On the other hand, fusion welding of most dissimilar alloys tends to be unsuccessful due to incompatibilities in their physical properties and melting points. Therefore, solid- state processes, such as diffusion bonding, explosive welding, and friction welding, are considered and commercially used to join various families of dissimilar materials. However, the solid-state diffusion bonding of copper alloys normally results in a substantial deformation of the alloy under the applied bonding load. Therefore, transient liquid phase (TLP) bonding, which requires minimal bonding pressure, was considered to join copper alloy (C18150) to a nickel-based superalloy (GH4169) in this work. BNi-2 foil was used as an interlayer, and the optimum bonding time (keeping the bonding temperature constant as 1030 °C) was determined based on microstructural examinations by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), tensile testing, and nano-hardness measurements. TLP bonding at 1030 °C for 90 min resulted in isothermal solidification, hence obtained joints free from eutectic phases. All of the tensile-tested samples failed within the copper alloy and away from their joints. The hardness distribution across the bond zone was also studied

Refinement of retained austenite in super-bainitic steel by a deep cryogenic treatment

The effect of a deep cryogenic treatment on the microstructure of a super-bainitic steel was investigated. It was shown that quenching the super-bainitc steel in –196°C liquid nitrogen resulted in the transformation of retained austenite to two phases: ~20 nm thick martensite films and some nano carbides with a ~25 nm diameter. Some refinement of the retained austenite occurred, due to formation of fine martensite laths within the retained austenite. The evolution of these new phases resulted in an increase in the average hardness of the super-bainitic steel from 641 to ~670 HV1

A new method for liquid-phase bonding of copper plates to aluminum nitride (AlN) substrates used in high-power modules

A new method for liquid-phase bonding of copper plates to an aluminum nitride (AlN) substrate was developed in this work. A newly developed proprietary interlayer composed of titanium and silver powders was deposited on the AlN substrate using a screen-printing machine. The eutectic reaction between printed silver and copper at 850 °C led to formation of a liquid phase at the joint interface. A total of 42 samples were prepared using seven and six different amounts of silver and titanium, respectively. The microstructures of all samples were analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy, and an ultrasonic flaw detector was used to assess joint integrity. The optimum composition of the Ti–Ag brazing alloy for producing defect-free joints was determined. The formation of a continuous titanium nitride layer was found to be essential for achieving sound joints between the copper plates and AlN substrate

A Feasibility Study on Using the Facilities of Health Centers for Developing a Laboratory Network on Vectors and Reservoir Hosts of Cutaneous Leishmaniasis in Iran

Background: Cutaneous leishmaniasis is an ancient endemic disease in Iran and continues to be a growing health threat to community development and the environment. This paper explains how to use the facilities of health centers for developing a laboratory network on vectors and reservoir hosts of cutaneous leishmaniasis in Iran. Methods: A literature search was performed of the relevant multiple databases to include studies on vectors and reservoirs of cutaneous leishmaniasis in Iran. A team of experienced experts was performed. After holding several meetings, field visits and organizing workshops, the activities of laboratories were determined at three levels. Results: Entomological studies showed that 5 species of the genus Phlebotomus and 10 species of the genus Sergentomyia are active in the south, 4 species of the genus Phlebotomus and one species of the genus Sergentomyia in the central part and 5 species of the genus Phlebotomus and 2 species of the genus Sergentomyia in the north east. Reservoir hosts were identified in the study areas. The tasks of laboratories were regulated at different levels. Conclusion: The Iranian Ministry of Health and Medical Education should prioritize the employment of capable persons in the field of Medical Entomology and Vector Control. The survival of this laboratory network depends on hiring and employing interested and persistent people. The universities of Medical Sciences that have the facilities to set up this network will be a very effective partner in the control of the disease in high risk areas. The results can be used in neighboring countries.Fil: Reza Yaghoobi Ershadi, Mohammad. Tehran University of Medical Sciences; IránFil: Akhavan, Amir Ahmad. Tehran University of Medical Sciences; IránFil: Reza Shirzadi, Mohammad. Iranian Ministry of Health and Medical Education; IránFil: Zohreh Hosseini, Seyedeh. Tehran University of Medical Sciences; IránFil: Salomón, Oscar Daniel. Secretaria de Gobierno de Salud. Instituto Nacional de Medicina Tropical. Instituto Nacional de Medicina Tropical - Sede Tucumán; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; ArgentinaFil: Hanafi Bojd, Ahmad Ali. Tehran University of Medical Sciences; IránFil: Rassi, Yavar. Tehran University of Medical Sciences; Irá

A Feasibility Study on Using the Facilities of Health Centers for Developing a Laboratory Network on Vectors and Reservoir Hosts of Cutaneous Leishmaniasis in Iran

Background: Cutaneous leishmaniasis is an ancient endemic disease in Iran and continues to be a growing health threat to community development and the environment. This paper explains how to use the facilities of health centers for developing a laboratory network on vectors and reservoir hosts of cutaneous leishmaniasis in Iran. Methods: A literature search was performed of the relevant multiple databases to include studies on vectors and reservoirs of cutaneous leishmaniasis in Iran. A team of experienced experts was performed. After holding several meetings, field visits and organizing workshops, the activities of laboratories were determined at three levels. Results: Entomological studies showed that 5 species of the genus Phlebotomus and 10 species of the genus Sergentomyia are active in the south, 4 species of the genus Phlebotomus and one species of the genus Sergentomyia in the central part and 5 species of the genus Phlebotomus and 2 species of the genus Sergentomyia in the north east. Reservoir hosts were identified in the study areas. The tasks of laboratories were regulated at different levels. Conclusion: The Iranian Ministry of Health and Medical Education should prioritize the employment of capable persons in the field of Medical Entomology and Vector Control. The survival of this laboratory network depends on hiring and employing interested and persistent people. The universities of Medical Sciences that have the facilities to set up this network will be a very effective partner in the control of the disease in high risk areas. The results can be used in neighboring countries.Fil: Reza Yaghoobi Ershadi, Mohammad. Tehran University of Medical Sciences; IránFil: Akhavan, Amir Ahmad. Tehran University of Medical Sciences; IránFil: Reza Shirzadi, Mohammad. Iranian Ministry of Health and Medical Education; IránFil: Zohreh Hosseini, Seyedeh. Tehran University of Medical Sciences; IránFil: Salomón, Oscar Daniel. Secretaria de Gobierno de Salud. Instituto Nacional de Medicina Tropical. Instituto Nacional de Medicina Tropical - Sede Tucumán; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; ArgentinaFil: Hanafi Bojd, Ahmad Ali. Tehran University of Medical Sciences; IránFil: Rassi, Yavar. Tehran University of Medical Sciences; Irá

Diffusion bonding of TiC or TiB reinforced Ti–6Al–4V matrix composites to conventional Ti–6Al–4V alloy

The diffusion bonding of conventional alloy Ti–6Al–4V (Ti-64) and composites of this alloy with 10% of TiC or TiB fabricated using blended elemental powder metallurgy was successfully carried out at 850–1000°C, with a holding time of 60 min under 0.7–1.5 MPa pressure. The metallographic and electron backscattered diffraction studies as well as the bending and microhardness tests across the bonds are presented as the evidence of joint integrity. The selected experimental parameters do not cause undesirable structural changes (degradation) in the base metals adjacent to the bond interface. Particle reinforcement at ∼10% did not appear to modify bonding parameters when compared to the unreinforced Ti-64 alloy