Dry Sliding-Friction and Wear Behavior of Hot-Extruded Al6061/Si3N4/Cf Hybrid Metal Matrix Composite.

The effects of reinforcement addition and hot extrusion on the microstructures, micro hardness, friction, and wear behavior of aluminium (Al) hybrid composite were investigated. Al6061 dispersed with electroless nickel-coated Si3N4 (6wt.%) and copper-coated carbon fiber (Cf) (1wt.%) hybrid composites was developed through stir casting followed by hot extrusion. Optical micro structural studies confirmed that the size of reinforcements decreased, and their orientations were in the extrusion direction. The decrease in the grain size (29%) of hybrid composites was larger than that in the grain size of matrix alloys under hot-extruded conditions. The synthesized hot-extruded Al6061 hybrid composite exhibited a lower coefficient of friction (51%) and high wear resistance (39%) compared with the hotextruded Al6061base alloy

Influence of Boron Content on the Solidification Structure, Magnetic Properties and Hot Mechanical Behavior in an Advanced As-Cast TWIP Steel

This research work reports the effect of boron micro-additions (180 and 470 ppm) on the solidification structure, magnetic properties and hot ductility behavior of an advanced low-carbon highly alloyed twinning-induced plasticity (TWIP) steel. For this purpose, three experimental TWIP steels were fabricated by melting commercial raw materials and casting into metallic molds. Solidification structure was characterized by means of optical and scanning electron microscopy techniques, and a statistical study was carried out to measure dendrite features. A vibrating sample magnetometer was used, at room temperature, to determine magnetic properties, and a X-ray diffraction analysis was performed in order to identify the related phases during magnetic measurements. Finally, the hot ductility in the as-cast condition was evaluated at 700, 900 and 1100 °C, under a constant strain rate of 0.001 s−1. The results indicate that boron micro-additions cause an overall refining solidification structure and austenitic grain size. However, as the boron content increases, segregation of this element promotes formation of ferrite and ε-martensite, leading to ferromagnetic behavior. Nonetheless, with subsequent hot- and cold-rolling, the single austenitic phase is achieved, and this behavior is eliminated. Hot tensile tests revealed that boron micro-addition is beneficial to the hot ductility behavior. The greatest influence was observed for the higher concentration of boron (470 ppm). In comparison with the steel without boron content, the reduction of area (RA) is more than the triple of the hot workability during straining at 900 °C. Thus, present results demonstrate that boron micro-addition has an excellent potential for refining dendritic microstructure and improving the hot-deformation behavior of present low-carbon highly alloyed TWIP steel