Creep behaviors of ASTM A36 welded joints

This research work aimed to observe the creep behaviors of the ASTM A36 welded joints. The microstructure and hardness of the base zone (BZ), heat affected zone (HAZ), and weld fusion zone (WFZ) were measured. Afterward, the residual stresses on the welded plate were observed to determine any lead to fatigue failure. The hot tensile tests were then performed to investigate the welded specimens' creep behaviors at varied strain rates and temperatures. The power-law model was applied to describe the creep behaviors at each testing condition. Finally, the scanning electron microscopic (SEM) images of the tested specimens were observed to identify breakage causes. The creep results showed that the weakest locations were found in the base (A36) zones. The areas prone to ductile fracture was the base zones close to HAZ

Effects of Tool Coatings on Energy Consumption in Micro-Extrusion of Aluminum Alloy 6063

The tool wear rate and energy consumption were typically unknown in micro-extrusion, which made it difficult to optimize the tool design for both the final part quality and production cost. This study investigated the effects of tool coatings on energy consumption in the micro-extrusion of aluminum alloy 6063. Three main factors were considered in this study: (1) tool coating types, (2) bearing length, and (3) extrusion ratio. The micro-extrusion finite element simulation model was developed and validated with the micro-extrusion experiment. The results showed that increasing bearing lengths led to the increase in tool wear rate and energy consumption for all the coating types. The decreasing coefficient of friction values of the tool-billet interface led to a decrease in energy consumption. High hardness values of the tool surface and low bearing lengths helped increase tool life. Low values of coefficient of friction and bearing lengths helped decrease energy consumption

Tribology in metal forming at elevated temperatures

International audienceThe tribo-characteristics of metal forming at high temperatures have not yet been well understood due to the complex nature of thermal, microstructural, interaction, and process parameters. This is a review paper on the effects of temperature, coating, and lubrication to the tribological characteristics in hot forming as well as the tribometers for different metal forming processes at elevated temperatures mainly based on the experimental work. The tribological behaviors of oxides in hot forming, such as rolling and stamping, were reviewed and presented. Some commonly used surface coatings and lubricants in hot forming were given. Many types of tribometer were selected and presented and some of them provided a great potential to characterize friction and wear at elevated temperatures. Nevertheless, more testing conditions should be further investigated by developing new tribometers. Eventually, experimental results obtained from reliable tribometers could be used in theory and model developments for different forming processes and materials at high temperatures. The review also showed the great potential in further investigations and innovation in tribology