Search

Al matrix composites (AMCs) have gained tremendous interest in the past decades due to their lightweight, superior mechanical and other physical properties. In this study, an ultrafine-grained Al2024/1 wt% TiC/1 wt% graphene nanoplatelets (GNPs) nanocomposite was fabricated through powder metallurgy. Synergetic effects of TiC and GNPs on the microstructural characteristics, mechanical properties and thermal conductivity were investigated in comparison with those of the matrix and TiC or GNPs singly reinforced Al2024 matrix nanocomposites. The Al2024/1 wt% TiC/1 wt% GNPs nanocomposite showed significantly improved mechanical properties with the compression yield strength of 370.2 MPa, ultimate compressive strength of 615.8 MPa and fracture strain of 8.6%, indicating a superior balance in the strength and ductility over TiC or GNPs singly reinforced Al matrix composite, since the distributions of both the TiC and GNPs in Al2024/1 wt% TiC/1 wt% GNPs nanocomposite were improved significantly. The significant mechanical property improvements are attributed to the synergistic reinforcing contributions from TiC and GNPs. The thermal conductivity of Al2024/1 wt% TiC/1 wt% GNPs nanocomposite stables at 55.0 W∙m-1∙K-1 without a further decrease compared with the composite singly reinforced with GNPs. • An ultrafine-grained Al2024–TiC-GNPs hybrid nanocomposite (AlTG) was fabricated. • Introducing TiC and GNPs benefits uniform dispersions of TiC and GNPs in AlTG. • The hybrid composite (AlTG) shows a superior balance in the strength and ductility. • Improved dispersions of TiC and GNPs explain better mechanical properties of AlTG. • Excellent thermal conductivity of AlTG is remained compared with other composites. [ABSTRACT FROM AUTHOR]

The interfacial morphologies play a crucial role in mechanical properties of laminated/bimetal composite. This study investigates the effects of heat treatments on the interfacial characteristics, mechanical properties and fracture behaviour of a 2205 duplex stainless steel/AH36 carbon steel bimetal composite with varying interface situations fabricated by the hot-rolling and subsequent heat treatments. The bimetal composite was annealed from 850 °C to 1150 °C in steps of 100 °C with soaking 1 h. Heterogeneities of grain size and element concentration exist in the microstructural evolution of bonding zone adjacent to interface after annealing treatments, which were observed by the optical microscope and scanning electron microscope (SEM) coupled with the energy dispersive X-ray spectroscopy (EDS). It was found that the diffusion transition zone of Cr and Fe alloy elements between component 2205 and AH36 steel layers present an increasing trend with the rise of annealing temperature. The results of conventional, shear and compact tensile test indicate that the tensile strength of 2205/AH36 bimetal composite gradually decreases but the fracture elongation increases with the rising annealing temperature, the thicker alloy element diffusion zone results in the stronger interfacial shear strength and better ductility of bimetal composite, but the thick and strong interface has less positive effect than the mechanical properties of bimetal composite itself on preventing the fatigue crack growth across the interface. [ABSTRACT FROM AUTHOR]

Abstract Copper (Cu) foils are extensively used in the electronics industry owing to their excellent electrical conductivity and high flexibility. In the present study, Cu foils with a thickness of 100 µm were annealed at 700 °C for 3, 6, 30 and 60 min to obtain different grain sizes. The edge cracking of Cu foils in micro rolling was systematically investigated, and the mechanism involved was discussed combining the effects of grain size and tensile properties. The results of tensile tests show that the tensile curves become increasingly discrete with the increase of grain size. Both the fracture stress and the fracture strain decrease, and the scatter of stress increases with the coarsening of grains. The tensile fracture surfaces of the specimens with grain sizes of 19 and 23 µm contain very few micro-dimples, while no micro-dimples are formed on the fracture surfaces of the tensile tested specimens with grain sizes of 33 and 43 µm. The results of micro rolling tests show that edge cracking does not generate in the specimens with grain sizes of 19 and 23 µm after micro rolling. However, the edge becomes increasingly wavy with the increase of grain size and rolling reduction. When the grain size is increased to 33 µm or greater, significant edge cracking occurs under all the rolling reductions of 30%, 51% and 70%. Grain size has a significant effect on the edge cracking of Cu foils in micro rolling, which evolves based on the ductile fracture mechanism. [ABSTRACT FROM AUTHOR]

Manufacturing metallic micro channels is a critical issue in micro-electromechanical systems (MEMS), such as micro reactors, micro heat exchangers, micro heat sinks, and fuel cell bipolar plates. An ultra-thin metal foil rolling for the fabrication of micro composite channels was proposed in this study, which is able to improve product functions and reduce operational costs. Copper/SS304L composite foils after annealing at 900 °C were used to form micro channels under different rolling reductions (29.1%, 43.8% and 50.0%), in which the thickness of copper and SS304L are 0.3 mm and 0.1 mm, respectively. Accordingly, the microstructure evolution, material deformation behaviours and mechanical properties of the samples after micro rolling were investigated. From the characterisation of the micro channel region on the copper side, a double fibre texture is produced parallel to the rolling reduction, including a relatively strong <111> fibre and a weak <100> fibre. Moreover, a relatively strong <111> fibre and three weak <100>, <110> and α fibres along the rolling direction can be identified on the SS304L side. The hardness of copper and SS304L increases with the increase of rolling reduction, due to the strain-hardening effect for copper, and accumulated dislocation and formation of strain-induced α' martensite for SS304L during micro rolling, respectively. It is noted that in the ridge region for all the samples, the left fillet is harder compared to the right fillet, indicating the asymmetry of material flow. • Cu/SS304L composite micro channels were fabricated with various rolling reductions. • Stretched Cu grain and refined Fe grain are obtained as rolling reduction increases. • Strong <111> fibre is identified on Cu and SS304L of micro channels along RD. • The strain-induced α′ martensite was formed in SS304L after micro rolling. • Hardness of copper and SS304L increases with the increase of rolling reduction. [ABSTRACT FROM AUTHOR]

A method is proposed to determine the accurate constitutive model of individual phase in multiphase steel with small phase size. The nanoindentation tests with continuous stiffness method (CSM) were implemented to obtain the hardness-displacement curves of the advanced high strength steel DP1180. The validity of the nanoindentation results was evaluated based on the EBSD results and classic indentation size effect (ISE) model. The extra loading of loading-displacement curves due to geometrically necessary dislocations (GNDs) was excluded based on the simple established model. The constitutive model of each phase was determined based on the corrected loading-displacement curves using the inversion method. The results of microstructure based simulation agree well with those of tensile tests, which proves the reliability and accuracy of the constitutive model of individual phase obtained from the method proposed in this study. [ABSTRACT FROM AUTHOR]