► The deformation of clad sheet in asymmetrical roll bonding was analyzed. ► The effect of mismatch speed ratio on interfacial microstructure was studied. ► The tension, peeling and micro-hardness ...test of clad sheet were performed.
The interfacial microstructure and mechanical properties of Cu/Al clad sheet fabricated by asymmetrical roll bonding and annealing were studied by scanning electron microscope equipped with energy dispersive X-ray detector, micro-hardness, tension and peeling test. The stress state of deformation zone was analyzed qualitatively to express the advantage of asymmetrical roll bonding. The results show that the asymmetrical roll bonding with larger mismatch speed ratio causes severe shear plastic deformation of component metals, and provides a good interface for atoms diffusion during annealing. The interfacial microstructure is improved and interfacial layer thickness increases. The roll bonding with larger speed ratio improves the ultimate tensile strength, elongation and peeling force of clad sheet, and reduces the micro-hardness of interfacial zone.
High-speed steel is widely used for cutting tools due to its convenience of preparation and cost-effectiveness. Previous research has shown that deep cryogenic treatments improve the mechanical ...properties of high-speed steel, due to the transformation of the residual austenite and the precipitation of carbide, while few studies have researched martensitic changes. The variations in martensite multi-level microstructures in AISI M35 high-speed steel, treated over different deep cryogenic time periods, were investigated in this study. Meanwhile, the effect of these variations on the mechanical properties of the selected steel was discussed. It was found that prolonging deep cryogenic time facilitated an increase in dislocation, low-angle grain boundary, and the coincident-site lattice boundary (especially the twin boundary) of martensite. The size of the martensite block (db) and lath (dl) decreased with deep cryogenic time. However, the effect on the microstructure was limited when the cryogenic treatment time exceeded 5 h. The increase in dislocation decreased the temperature for carbide precipitation and promoted fine carbide precipitation during tempering. The refinement of martensite multi-level microstructures and the greater precipitation of fine carbides gave the tempered specimens excellent impact toughness. The impact toughness of the tempered samples undergoing deep cryogenic treatment for more than 5 h was about 32% higher than the sample without deep cryogenic treatment.
The interface bonding method has a great influence on the mechanical properties of aluminum foam sandwich (AFS). This study aims to investigate the effect of different interface bonding methods on ...the mechanical properties of AFS. In this paper, the metallurgical-bonding interface-formation mechanism of AFS prepared by powder metallurgy was investigated. The shear properties of metallurgical-bonded AFS were determined by the panel peeling test. The flexural properties and energy absorption of metallurgical-bonded and glued AFS were analyzed through the three-point bending test. The results show that the magnesium, silicon, and copper elements of the core layer diffuse to panels and form a metallurgical composite layer. The metallurgical-bonding strength between the panel and core layer is higher than that of the foam core layer. The peak load of metallurgically-bonded AFS is 24% more than that of glued AFS, and energy absorption is 12.2 times higher than that of glued AFS.
The tension tests of Al/Cu/Al laminated composites produced by asymmetrical roll bonding were performed at different strain rates from 10−3s−1 to 10−1s−1. It is found that the strength and elongation ...are enhanced with increasing strain rate. The interfacial improvement can be interpreted as the strengthening and toughening reason.
Deep cryogenic treatment applied in high-speed steel yielded promising results, and it was found that tempering played a vital role. This paper systematically studied the effect of tempering ...temperatures on the microstructural composition (residual austenite, martensite, and carbides) and mechanical properties (Vickers hardness and impact toughness) of AISI M35 high-speed steel subjected to deep cryogenic treatment. An increase in the tempering temperatures facilitated the transformation of residual austenite and the formation of martensite blocks corresponding to a decrease in the number of dislocations. Moreover, the carbide precipitation (secondary carbides and nanoscale carbides) began at a tempering temperature of 350 °C, increased at 450 °C, and reached its maximum at 550 °C. The fracture mechanism on the micro-level could be interpreted as follows: cracks occurred in the carbides with larger sizes (primary carbides and large secondary carbides) and at the carbide/matrix interface, and small secondary carbides decohered at the interface, forming microvoids and facilitating plastic deformation. In addition, the specimen tempered at 150 °C exhibited the highest hardness of 880.4 HV1 due to the highest number of dislocations. The impact toughness of the sample tempered at 550 °C was the best, namely 2.50 MJ m−2, due to an increase in the number of martensite block boundaries and the more homogeneous carbide precipitation.
This paper employs an innovative investigation approach to study pore evolution in Al-Si-Mg-Cu alloy within aluminum foam sandwiches (AFS) by integrating data from heating–expansion ratio curves, in ...situ observation of synchronous radiation, and microscopic analysis of the matrix’s microstructure at different stages. Additionally, the cavity design and plate type control for large-scale AFS production are explored. Findings categorize the precursor heating into three stages: rapid heating, solid–liquid transition, and stable foaming. During solid–liquid transition, the expansion rate experiences a sudden drop, associated with pore nucleation and edge cracking of precursors. Pores nucleate as elongated crack-like structures along the rolling direction, guided by the Mg-enriched regions. In stable foaming, these pores evolve, become spherical, and the matrix rapidly expands. Using square tubes for sealing on the preform cavity sides creates a dense edge zone during rolling, halting crack propagation into the powder core. Adopting edge sealing during foaming mitigates boundary effects, thereby improving AFS panel flatness.
Using the powder-metallurgy rolling method, aluminum foam sandwich (AFS) panels with a metallurgical bond between the foam core and the panel can be produced. In this study, by manipulating the ...foaming temperature and duration, AFS panels were fabricated with varying core densities and thicknesses, all maintaining a panel thickness close to 1 mm. Through the three-point bending test, this research deeply delved into how core density influences the mechanical behaviors of these AFS panels. It became evident that a rise in core density positively affects the bending strength and failure load of the panels but inversely impacts their total energy absorption efficiency. Differing core densities brought about distinct failure patterns: low-density samples primarily showed panel indentation and core shear failures, whereas those of high density demonstrated panel yield and fractures. Furthermore, the research offers predictions on the initial failure loads for different failure modes and introduces a comprehensively designed failure diagram, laying a foundational theory for the production of AFS panels.
We investigate the tensile properties of Al/Cu/Al laminated composites produced by asymmetrical roll bonding. In comparison with the conventional rolled composites, the strengthening of asymmetrical ...rolled composites with slightly reduced elongation arises from the improved interfacial microstructure and intermetallic compounds. Moreover, the interface strengthening effect causes higher strain rate sensitivity.
A novel constitutive model for predicting the compression behaviors of closed-cell Al foam was proposed. In contrast to existing models, it gives a nonlinear stress-strain response, which is in ...accordance with the hardening behaviors of foam. The new constitutive relation is derived based on the mean-field approximation and isothermal reversible compression approximation of ideal gas. Except for the overestimated densification behavior, good agreement is observed between the stress-strain curves and the predictions of the model.
In this paper, an aluminum foam sandwich (AFS) was prepared by the rolling composite-powder metallurgy method, and its fatigue properties were studied. It was compared with an AFS made by the ...adhesive method to study its fatigue properties more directly. In this experiment, the fatigue performance was investigated by studying the microscopic interface, fatigue life, deflection curve, and failure mode. The results show that the fatigue life of an AFS with the rolling composite-powder metallurgy method is much longer than that with the adhesive method. The failure mode of an AFS made by the rolling composite-powder metallurgy method is shear failure, and that of an AFS made by the adhesive method is shear failure and interface debonding. An AFS with the rolling composite-powder metallurgy method has better fatigue properties. This paper also explored the fatigue damage model using the fatigue modulus method, and the polynomial fitting method has a higher fitting degree.
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