[en] Highlights: • Lattice distortion and grain refinement occurred in the damage layer of the steel. • Amorphous region formed locally in the bubble layer at a fluence of 1 × 10¹⁸ions/cm². • Carbide particles showed a tendency to decompose under the irradiation. • Surface damage threshold of CLF-1 steel was at the fluence of 1 × 10¹⁸He/cm².

[en] Short communication

[en] The intangible role of titanium and aluminium diboride in the nucleation of aluminium was re-examined. Two different techniques, complemented with scanning electron microscopy, allowed determining the stability of the diboride in the presence of titanium tri aluminides and liquid aluminium phases. Through rapid scintillated quenching the high temperature diboride were retained and studied. Then, in a diffusion couple, the reactivity of such diboride was tested in contact with pure titanium tri aluminide. It is proposed that a ternary diboride acts as the main catalytic particle in the crystallization of aluminium alloys with refined grains. (Author) 27 refs

[en] Highlights: ► The reinforcement effect of {101^¯2} twins on yield stress is reflected at low deformation. ► The recompressive yield stress equals to the stress when it is unloaded. ► The stress–strain curve of recompression seems like that without interruption. ► Twins generated in precompression could become thicker in recompression. -- Abstract: The current paper investigates the effect of {101^¯2} extension twins identified by using electron backscattered diffraction on the interrupted properties of an extruded Mg–3Al–1Zn (AZ31) alloy. Compressive and recompressive tests are conducted along extrusion direction (ED). It is discovered that the yield strength of recompression is enhanced due to grain refinement by {101^¯2} extension twins. The reinforcement effect of {101^¯2} extension twins on the yield stress of recompression is mainly reflected at the stage of small deformation while the improvement of yield strength is mainly attributed to the pile-up and intersection of dislocations as large deformation occurs. Furthermore, the yield stress of recompression is identical to the interrupted stress of precompression. In situ observation reveals that some twins generated in precompression could also become thicker in the following recompression.

[en] The microstructure evolution of the 190 μm-thick Cu foils subjected to repeatedly bending loading was investigated. We found that the grains in the micron-scale foil were refined into subgrains with a size of about 0.5 μm through a removal of twin boundaries and an introduction of a high frequency of high angle boundaries (>15°) with accumulative cyclic deformation. With increasing strain rate (loading frequency), the grains are completely refined into well-defined fine grains with high angle boundaries. Such the microstructure refinement induced by accumulative cyclic deformation may provide a potential strategy for grain refinement of small-scale materials. (paper)

[en] The quantity, distribution and effectiveness of eutectic carbides was studied in high niobium microalloyed steels. The particles showed extremely inhomogenuous distributions and seemed to be ineffective in promoting refinement of either an austenitic, ferritic or perlitic microstructure. There is a definite need for better quantitative data about the fraction of Nb 'lost' to eutectic particles in these steels. (Author)

[en] Highlights: • KoBo extrusion significantly increases the strength of pure zinc. • The improvement in the strength is related to a much lower deformation temperature. • The increase in properties is higher for the ingot batch than the hot extruded batch. The microstructure and properties of cast and hot extruded zinc subjected to plastic deformation by conventional extrusion and by extrusion with a forward-backward rotating die (KoBo) were studied. KoBo significantly increased the mechanical properties of both initial materials compared with conventional extrusion. The improvement of the mechanical properties is related to the lower temperature at which the KoBo process can be carried out. Extrusion with a forward-backward rotating die leads to grain refinement and promotes the formation of a composite-like microstructure with a hard matrix, forming an interconnected network of boundaries filled with a softer phase. New areas of application for zinc obtained by the KoBo method are opened.

[en] In order to investigate the effect of aging on twin boundary (TB) strengthening in magnesium alloys, the cyclic compressions along two orthogonal directions of samples with and without intermediate aging are carried out. The results show that the grains in all Mg alloys AZ31, AZ61 and AZ91 are significantly refined by twin boundaries (TBs). The TB strengthening is strongly dependent on both alloying element content and aging. Although grain refinement by TB formation occurs in AZ31, it exhibits slight strengthening effect even after aging. In contrast, significant TB strengthening after aging is observed in Mg alloys AZ61 and AZ91 with high contents of alloying elements.

[en] Conical samples of a Mg-3.8%Zn-2.2%Ca alloy undergoing the columnar to equiaxed transition, induced by the addition of 1.5%Zr, have been examined. The zirconium contents in the equiaxed grains just ahead of the columnar front were found to generally vary between 0.2% and 0.3%. Further assessment confirmed that, as the first step towards optimum grain refinement, a zirconium content of 0.22% was necessary for the formation of equiaxed grains in the experimental alloy under conditions similar to sand casting

[en] Grain refinement of cast magnesium alloys containing Al is successfully attained using MnCO_3 as a grain refiner. However, the direct addition of MnCO_3 in a magnesium melt causes the oxidation and ignition of the melt due to the gases that formed during the decomposition of MnCO_3. To improve the effectiveness and safety of the MnCO_3 addition process, inoculation was conducted by adding an Al master alloy with MnCO_3. The Al master alloy was prepared using cylindrical pressed pellets composed of a mixture of MnCO_3 powders and metal chips in the aluminum melt. The results revealed that the inoculation method using the Al master alloy is more effective and stable than previously used methods. The grain size of the as-cast AZ91 Mg alloy was significantly decreased from 420 to 70um by adding the Al master alloy of 3 wt%, which is mainly attributed to the formation of thermally stable Al_4C_3 particles as an effective grain refiner in the melt.