Equal channel angular pressing (ECAP) was conducted on the two grades of low carbon steel, with or without vanadium, in order to produce an ultarfine grained structure. As a result, the ferrite grains were refined from 30 mm to 0.2ϳ0.3 mm. The strength of the ECAPed steels increased remarkably, over twice of the strength of the steels before ECAP. A series of static annealing experiments showed that the increment of ECAP strain and the dilute addition of microalloying element such as vanadium were very effective on enhancing thermal stability of the ultrafine gained low carbon steels produced by ECAP in terms of microstructure and tensile properties. This enhanced thermal stability resulted from; (a) presence of excessive carbon content in the ferrite matrix by carbon dissolution from pearlitic cementite during ECAP; (b) preservation of high dislocation density due to addition of vanadium, providing the effective diffusion path for dissolved carbon atoms; (c) precipitation of excessive carbon as the form of nano-sized cementite particles during subsequent annealing and its effect on suppressing grain growth.
Cleaning acrylic emulsion paintings is challenging because of the material properties of the paint films, including their solubility. The goal of this work was to learn more about the effect of aqueous treatments on acrylic paints. Paint manufacturers were asked for their recommendations for cleaning these paintings and conservators were asked to comment on the damage observed in them and on the treatments applied. Responses showed that aqueous cleaning treatments are used, despite the associated risks, and that more technical information is needed about the effects of cleaning. The experimental section of this paper evaluated the changes in physical and mechanical properties of aged cobalt blue paint as a result of exposure to aqueous cleaning solutions. The results indicated that short immersions in these solutions caused a drop in most mechanical properties, but longer immersions did not; the drop after the short immersions was mostly due to the great increase in dimensional thickness of the paint films. Longer conservation treatment times are not being advocated.
Aluminum based metal matrix composite (MMC) was processed by accumulative roll bonding (ARB) for ultra grain refinement and high strengthening. The ARB process up to 4 cycles was performed for the composite with 5vol.%SiC at ambient temperature under unlubricated conditions. The ARB of unreinforced aluminum powder compact was also performed for comparison. The tensile strength of the composite increased with the number of ARB cycles, and reached a maximum of 375MPa at the 3rd cycle, which is 1.8 times higher than that of the initial material. An increment of the strength per cycle was much larger in the composite than that in the unreinforced 6061 aluminum powder compact. The elongation of the composite decreased gradually with the number of ARB cycles, became almost zero after 4 cycles. TEM observation revealed that the composites fabricated by 1 to 3 cycles showed a dislocation cell structure, but after 4 cycles it showed an ultra-fine grained structure with mean grain size below 500nm. The ultra-fine grains developed at lower cycles in the composite than in the unreinforced one.
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