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A new process, sheathed powder compaction (SPC), was proposed to fabricate hybrid metallic composite samples at room temperature. The process involves densification of fine powder in an annulus sheath under combined moderate pressure and shear. Hybrid samples of copper annular with aluminum powder were produced to demonstrate the merits of the process. The fabricated samples were characterized and explored using electron microscopy, micro hardness, micro shear punch tests and density ratio measurements. Comparing “shear punch response” of the samples in the Al region with those of commercially pure aluminum and Al 5005-H34 samples showed an excellent shearing strength in the region. The electron backscatter diffraction analyses and scanning electron microscopy observations suggested that the substantially enhanced strength was facilitated by a significant SPC induced grain refinement. Moreover, the annular sheath (copper) also showed significant grain refinement due to the process. These demonstrated promising potentials of the SPC to manufacture hybrid metals with concurrent grain refinement at room temperature under moderate processing conditions.

A copper clad aluminum composite sample fabricated by an Axi-symmetric Forward Spiral Composite Extrusion (AFSCE) process was analyzed using finite element models of a dedicated blanking test. The axi-symmetric composite sample was analyzed using various interfacial characterization techniques, which revealed a near flawless interface between copper and aluminum in the AFSCE sample. The dedicated blanking test (DBT) was designed to measure the bonding shear strength of the metallic composite sample. To identify the required design parameters of the test rig, a preliminary Finite Element (FE) model was developed using Abaqus finite element package. The effect of the design parameters including sample thickness, blanking clearance and fillet radii of the tools were determined to develop a large and more uniform strain along the interface and avoid bending of the metallic composite sample. The numerical results showed that the sample thickness, clearance and fillet radii have a significant effect on the measured bond shear strength and the location and magnitude of maximum strain during the blanking test. The composite copper clad aluminum bond shear strength was experimentally determined using the newly designed test rig. After that, a detailed finite element model using cohesive modeling technique was utilized to model the shear strength distribution of the metallic composite during the blanking test.

Fabrication of metal-based composites with concurrent grain refinement is an exciting and novel avenue in hybrid metal manufacturing. Copper clad aluminum rods, that were fabricated using Axi-Symmetric Forward Spiral Composite Extrusion (AFSCE) are investigated here as an example. Careful investigations of the bonding mechanism in the AFSCE samples are needed to control mechanical and physical properties of the composite material. In order to understand the mechanism of the bonding between copper and aluminum in the AFSCE process, morphological and micro-structural investigations were conducted by using a Scanning Electron Microscope/Focused Ion Beam (SEM/FIB) dual ion microscope and X-ray diffraction to study the nature of the interface. Hardness measurements across the interface region of the AFSCE sample were also produced to examine the deformation mechanism. A near flawless interface, without significant intermetallic or oxide layer, was identified. The strength variation in the copper region was characterized using micro-hardness tests which agreed well with the Electron Backscatter Diffraction (EBSD) observations of various sampling points. It was also found that the micro-hardness values near the interface and the outer periphery regions of the copper were higher than the hardness values at the middle region of the material, which is approximately equal to that of unprocessed copper.

A dedicated blanking test (DBT) was designed to measure the bonding shear strength of a metallic hybrid sample. To identify the required design parameters of the rig, a macro numerical model was developed using Abaqus Finite element (FE) package. Copper clad aluminum hybrid samples fabricated by an axi symmetric forward spiral composite extrusion (AFSCE) process were analyzed using the developed numerical model. The effect of the design parameters including sample thickness, blanking clearance and the die and punch fillet radii were determined to ensure a pure shear blanking along the interface. The numerical results showed that the sample thickness, clearance and fillet radii have a significant effect on the measured bond shear strength and the location of the failure. The required rig was designed and composite copper clad aluminum bonding shear strength was experimentally determined based on the numerical findings.

An axi-symmetric forward spiral composite extrusion (AFSCE) method is proposed to produce hybrid rods. This process involves extrusion of a composite sample through a die with engraved spiral grooves to create a near net shape product. The process can be easily performed and has better dimensional control than the existing bimetallic rod fabrication processes because of the zero shape change effect of this process. An analytical solution of shear deformation during AFSCE in the radial direction of the hybrid sample is first presented. To demonstrate the production of composite rods using the process, an experimental case study of an Aluminum and Copper (Al/Cu) sample at elevated temperature and in the presence of a back pressure is presented. Microstructure characterizations of the Al/Cu interface and the neighboring regions revealed the formation of a bonded layer with the possibility of intermetallic compounds present at the interface. Composite blanking proved good bonding strength between the parent materials. The results show that the AFSCE process has strong potential to be utilized for the fabrication of hybrid metal rods.

A rapid method was used to identify kinetics of the recrystallization for two IF (Interstitial Free) steels which have different phosphorous and boron contents. The static and metadynamic softening behaviour of the materials for a range of strain rates and temperatures were quantified. The critical strain for initiation of strain independent softening was estimated for the IF steels in respect to the time for 50 percent softening after deformation. The results showed that the strain for the initiation of strain independent softening (often referred to as metadynamic recrystallization) varies with the Zener Hollomon parameter. Classic static recrystallization was observed at strains below the strain independent softening for all processing conditions and the strain rate had a strong effect on the time for strain independent softening. Results also revealed that static and metadynamic recrystallization was delayed owing to the phosphorous and boron alloying elements. Hence, the large strain at above no-recrystallization temperature may be required for the early stage of Finishing Stands Unit (FSU) in hot strip rolling mills to initiate austenite grain refinement of phosphorous and boron added IF steels.