This review article aims to provide an updated and comprehensive description of the development of the Electric Current Activated/assisted Sintering technique (ECAS) for the obtainment of dense materials including nanostructured ones. The use of ECAS for pure sintering purposes, when starting from already synthesized powders promoters, and to obtain the desired material by simultaneously performing synthesis and consolidation in one-step is reviewed. Specifically, more than a thousand papers published on this subject during the past decades are taken into account. The experimental procedures, formation mechanisms, characteristics, and functionality of a wide spectrum of dense materials fabricated by ECAS are presented. The influence of the most important operating parameters (i.e. current intensity, temperature, processing time, etc.) on product characteristics and process dynamics is reviewed for a large family of materials including ceramics, intermetallics, metal–ceramic and ceramic–ceramic composites. In this review, systems where synthesis and densification stages occur simultaneously, i.e. a fully dense product is formed immediately after reaction completion, as well as those ones for which a satisfactory densification degree is reached only by maintaining the application of the electric current once the full reaction conversion is obtained, are identified. In addition, emphasis is given to the obtainment of nanostructured dense materials due to their rapid progress and wide applications. Specifically, the effect of mechanical activation by ball milling of starting powders on ECAS process dynamics and product characteristics (i.e. density and microstructure) is analysed. The emerging theme from the large majority of the reviewed investigations is the comparison of ECAS over conventional methods including pressureless sintering, hot pressing, and others. Theoretical analysis pertaining to such technique is also proposed following the last results obtained on this topic.

Consolidation/synthesis of materials by electric current activated/assisted sintering

Mechanically alloyed nanocomposites

Analysis of process parameters effects on friction stir welding of dissimilar aluminum alloy to advanced high strength steel

http://iesys.skku.ac.kr/es/International%20Journal/8.pdf

Optimal cylindrical handle diameter for grip force tasks

Cold metal transfer joining aluminum alloys-to-galvanized mild steel

The toughening of Fe–Al intermetallic compound coating formed by aluminizing of carbon steel was investigated. The growth mechanism, morphology and mechanical properties of Fe–Al intermetallic compound layers on the surface of carbon steel were systematically evaluated for specimens diffused at temperatures ranging from 873 to 1323 K after hot dip aluminizing. Fe2Al5 was mainly formed on the specimen surfaces at the usual diffusion temperatures from 873 to 923 K. However, FeAl and Fe3Al layers having relatively high fracture resistance and oxidation resistance properties were preferentially formed in the specimens diffused at temperatures greater than 1273 K. The activation energies required for the growth of the FeAl and Fe3Al layers were QFeAl=180 and QFe3Al=260 kJ mol−1, respectively. It was identified that the formation and growth of Fe–Al intermetallic compound layers is controlled by the diffusion of Fe atoms into the intermetallic compound layers.

Control of intermetallic compound layers at interface between steel and aluminum by diffusion-treatment

Foil aluminizing of steel, wherein Al diffuses to the base steel material by diffusion treatment after hot pressing of the aluminum foil at a lower temperature than the melting point, was performed in this study. Alloy layers formed by diffusion at temperatures ranging from 700 to 1000 °C were investigated, and their features were compared with those of hot-dip aluminized steel. In hot-dip aluminizing, an intermediate Fe 2 Al 5 layer was formed between the aluminum layer and the base steel during aluminum coating before the diffusion treatment. In contrast, the coating layer of the foil-aluminized steel specimen after diffusion bonding of the aluminum foil consisted only of the Al layer. An Fe 2 Al 5 layer, an FeAl layer and an Al diffused layer were formed in both the aluminized specimens subsequent to the diffusion treatment. The numbers of voids formed in the Fe 2 Al 5 layer and at the FeAl/Al diffused layer interface of the foil-aluminized specimens are smaller than those for hot-dip aluminizing. Moreover, the FeAl and Al diffused layers are formed with a greater thickness in the foil-aluminized steel under identical diffusion conditions. The Al concentration in hot-dip aluminized steel decreased in stages from the surface to the base steel, whereas, in the foil-aluminized steel, it decreased gradually. The Fe 2 Al 5 /base steel interface in the foil-aluminized steel was thus indistinct, and cross-sectional hardness also decreased gradually.

Features of intermetallic compounds in aluminized steels formed using aluminum foil

In order to clarify the grasping mechanism of tools and machine handles, sensory tests to evaluate the optimum grasping diameter have been performed on forty-three people from age seven to fifty-three. It was confirmed that the sensory evaluation of the optimum grasping diameter was difficult for children under age ten due to insufficient growth of skeletal structure. The optimum grasping diameter was evaluated for persons above age ten. The optimum grasping diameter depended on the hand size, and the dependency was marked for children under eleven. In the case of adults, the optimum grasping diameter depended on the dimensions concerned with the length of the hand but only depended slightly on the hand breadth or fist. The optimum grasping diameters evaluated for males were 30∼40mm, which were about 10% larger than those evaluated for females. As a result of investigating above data, it was found that the tube could be grasped well by a human hand if all fingertips and the entire palm area contact it.

Sensory Evaluation of Grip Using Cylindrical Objects.

To evaluate chip breakability, turning tests for various wrought aluminum (Al) alloys were carried out with a cemented carbide tool (K10) in dry and wet cutting conditions In the alloys, Al2Cu, Al6Mn, Mg2Si, Al–Fe–Si system compounds and eutectic Si were observed as second-phase particles Chip breakability of the alloys containing Al2Cu or Si were superior to those of those containing Mg2Si or Al–Fe–Si This tendency was more prominent in wet cutting than in dry cutting The second-phase particles of Al2Cu and Si in these alloys fractured during the machining process It was estimated that the fractured second-phase particles acted as the cause of chip breaking Moreover, the increase of the chip breakability in wet cutting was attributed to the Rehbinder effect due to the penetration of cutting oil into the micro-cracks

Role of second-phase particles in chip breakability in aluminum alloys

Room-temperature yield strength of powder-metallurgy Al-ceramic particle composite alloys produced by mechanical alloying was analyzed from a viewpoint of microstructure which was characterized by several features: high dislocation density (in the order of 1014 m–2), uniform dispersion of fine Al4C3 and Al2O3 particles (35 nm in size) and coarse ceramic particles (0.4-1.0 μm), and small grain size (0.5 μm). A large portion (more than 80%) of yield strength was concluded to be contributed through dispersion hardening by the fine particles and particle reinforcing by the coarse particles; the contribution was greater through the former mechanism than through the latter one for a given volume fraction of particles. The former mechanism was based on detaching pinned-down dislocations at the fine particles from them, and the latter one on restricting matrix deformation by mechanical constraint around the coarse particles. Impurities in the Al matrix made a modest contribution to strength, probably through solution hardening. These mechanisms raised the strength additively. Work hardening due to a high density of dislocations introduced during processing and grain boundary strengthening due to small grain size were considered not to be principal mechanisms for determining the yield strength.

https://www.jstage.jst.go.jp/article/isijinternational1989/32/8/32_8_902/_pdf

Takao Yakou

Papers

Control of intermetallic compound layers at interface between steel and aluminum by diffusion-treatment

Features of intermetallic compounds in aluminized steels formed using aluminum foil

Sensory Evaluation of Grip Using Cylindrical Objects.

Role of second-phase particles in chip breakability in aluminum alloys

Strengthening mechanisms in aluminum-ceramic particle composite alloys produced by mechanical alloying