In this article, the authors investigate the effectiveness of glass and metal recycling in Roman towns. The comparison of sealed primary deposits (reflecting what was in use in Roman towns) with dumping sites shows a marked drop in glass and metal finds in the dumps. Although different replacement ratios and fragmentation indices affect the composition of the assemblages recovered in dumps, recycling appears to have played a fundamental role, very effectively reintroducing into the productive chain most glass and metal items before their final discard. After presenting a case study from Pompeii, the authors examine contexts from other sites that suggest that recycling practices were not occasional. In sum, recycling should be considered as an effective and systematic activity that shaped the economy of Roman towns.

In the first millennium AD, peoples across the North American Arctic began to use and exchange metal. A group known as the Late Dorset (AD 500–1300) were the first to widely exchange metal in the Eastern Arctic. However, due to differential taphonomic processes and past excavation methods, metal objects in existing collections are rare although geographically widespread. This has led to metal being seen as a broadly exchanged but uncommon raw material among Late Dorset. This article expands the known scale of Late Dorset metal use by analyzing the blade slot thicknesses of bone and ivory objects from sites across the Eastern Arctic and comparing them to the thicknesses of associated lithic and metal endblades. These results demonstrate that Late Dorset used metal at least as frequently as stone for some activities. Given the few and geographically discrete sources, metal would have been exchanged over thousands of kilometers of fragmented Arctic landscape. The lack of similar evidence in earlier periods indicates intergroup interaction increases significantly with the Late Dorset. It is through these same vectors that knowledge and information would have flowed. Metal, consequently, represents the best material for understanding the maximum extent and intensity of their interaction networks.

In this study, the quasi-static and dynamic mechanical behaviors and the energy absorption capacity of closed-cell aluminum foams with uniform and graded densities were experimentally studied. The effects of density, strain rate, and graded density on the mechanical performances of aluminum foams were quantitatively evaluated. It was shown that the density had a significant effect on the quasi-static and dynamic compressive stress of aluminum foams. Moreover, impact compression experiment results revealed that aluminum foam was sensitive to the strain rate. As the strain rate increased, the plateau stress and energy absorption capacity increased distinctly and the rate of deformation increased correspondingly. Finally, the investigation of aluminum foams with uniform and graded densities to study their deformation and failure mechanisms, mechanical characteristics, and energy absorption capacities showed that the GD 0.48-IV specimen exhibited superior impact resistance. The present work can provide a valuable reference for the optimum design of aluminum foam against impact loading.

Observation of the dynamic interaction between dislocations and carbon atoms is important in steel design. Some steel materials are bake-hardened in several manufacturing processes. Solute carbons are known to segregate on dislocations; this hardens the steel even after low-temperature treatments. The purpose of this study was to develop a method of monitoring a series of microstructural changes in strain aging by in-situ measurement of the electrical resistance in low-carbon steel. In tensile deformation, elastic, Lüders, and uniform plastic deformations could be distinguished by monitoring the changes in electrical resistance. Electrical resistance rapidly increased in the plastic deformation region in the strain-aged specimen. Although the deformation stress hardly changed, the amount of lattice defects monotonously increased. These analyses provide useful information in steel design related to thermomechanical treatments of bake-hardenable steel.

Any material inherently comes with its physical and chemical properties. The material scientists and allied engineers work on these properties in order to unearth newer findings. The change in the properties of a material through various process directly affects its characteristics and behaviour. Significant research on material science and metallurgical engineering have been done based on physical properties of the substance. Out of many physical characteristics of materials, this paper focuses on optical properties based on human visual perception. The particular research aims at an interdisciplinary approach to investigate how visual perception plays an important role in design and analysis of materials. Two particular cases have been analysed for this purpose, one in the domain of micro structure analysis and the other relating to the external physical visual characteristics of a material. Through this analysis a generic process framework is evolved which could be applied in material research as a theoretical discourse. Additionally an expert opinion survey reinforces the establishment of the evolved process framework. It would help scientists and engineers adapt and relate to a process so far as designing of new materials or comparative assessment of materials are concerned based on human visual perception.

While fast-switching rewritable nonvolatile memory units based on phase-change materials (PCMs) are already in production at major technology companies such as Intel (16–64 GB chips are currently available), an in-depth understanding of the physical factors that determine their success is still lacking. Recently, we have argued for a liquid-phase metal-to-semiconductor transition (M-SC), located not far below the melting point, Tm, as essential. The M-SC is itself a consequence of atomic rearrangements that are involved in a fragile-to-strong viscosity transition that controls both the speed of crystallization and the stabilization of the semiconducting state. Here, we review past work and introduce a new parameter, the “metallicity” (inverse of the average Pauling electronegativity of a multicomponent alloy). When Tm-scaled temperatures of known M-SCs of Group IV, V, and VI alloys are plotted against their metallicities, the curvilinear plot leads directly to the composition zone of all known PCMs and the temperature interval below Tm, where the transition should occur. The metallicity concept could provide guidance for tailoring PCMs.

With growing demand for better fuel economy for automobiles, multimaterial solutions are increasingly being utilized in the automotive industry for reducing weight in the vehicle body structure. This poses challenges in terms of joining dissimilar metals, especially those with vastly different properties such as aluminum to steel joining. General Motors has developed a new resistance spot-welding technique for dissimilar materials using a multi-ring domed (MRD) electrode and multiple solidification weld schedules to address this challenge. Originally developed for aluminum to aluminum resistance spot welding, this technology is being deployed as the mainstream aluminum joining solution to leverage existing infrastructure and workforce competency in resistance spot welding. With the recent expansion of MRD technology to aluminum to steel resistance spot welding, there is an ever-greater need to experimentally verify the quality of each aluminum to steel resistance spot-weld application with limited time and resources. Nondestructive evaluation (NDE) would enable the transfer of resistance spot-welding technology to dissimilar aluminum to steel joints. This article describes the current state of the art of aluminum to steel resistance spot welding and the challenges in developing a robust NDE process for this technology.

Lightweighting of vehicles and portable structures is an important undertaking. Multimaterial design is required to achieve conflicting design targets such as cost, stiffness, and weight. Friction stir welding (FSW) variants, such as friction stir dovetailing and friction stir scribe, are enabling technologies for joining of dissimilar metals. This article discusses how FSW variants are capable of joining aluminum to steel in particular. The characteristics of metallurgical bonding at the dissimilar materials interface are strongly affected by weld temperature. Control of FSW process temperature enables metallurgical bonding with suppressed formation of intermetallics at the dissimilar materials interface, resulting in improved mechanical properties relative to competing techniques. Temperature control is thus a powerful tool for process development and ensuring weld quality of dissimilar materials welds.

At GE Research, we are combining “physics” with artificial intelligence and machine learning to advance manufacturing design, processing, and inspection, turning innovative technologies into real products and solutions across our industrial portfolio. This article provides a snapshot of how this physical plus digital transformation is evolving at GE.

A novel high-power impulse plasma source (HiPIPS) technology that combines atmospheric pressure plasma jets with high-power pulsed direct current generators is described. Pulsed power is applied in microsecond pulses (20 µs) at low duty cycle (10%) and low frequency (0.5 kHz) leading to high peak power densities (10–75 kW) and high peak currents (100–250 A) while maintaining low average power (<40 W) and low processing temperatures (<50 °C). These conditions result in the generation of a highly dense plasma discharge (ne = 6.23 × 1016 cm−3) for surface modification and deposition of coatings. Using HiPIPS, Ar-initiated metallic Ti, CoCr, or Ti–6Al–4V plasma was generated, and the plasma properties were characterized by measuring current–voltage characteristics, electron densities (Langmuir probe), and optical emission spectra. HiPIPS CoCr and Ti–6Al–4V coatings were deposited for proof of concept of the technique. The resulting coatings were examined with scanning electron microscopy, energy-dispersive X-ray spectroscopy, and nanoindentation.