[en] Objective: To evaluate the 3-dimention (3D)CTA, MRA and DSA imagings in the application of dense packing for curing aneurysm. Methods: 64 patients with intra-cranial aneurysms were treated with clipping or endovascular techniques (including 72 aneurysms with 60 intravascular embolizations). Their 3D images were studied, the characteristics of CTA MRA and DSA were compared. Results: Among 72 aneurysms, 60 were packed with dense packing in 50 patients, >95% packing in 10 cases. The measurement of aneurysm in 3D-CTA showed bigger than that of 2D-DSA; and that of 3D-DSA was bigger than that of 2D- DSA. Conclusion: Aneurysms could be obliterated by endovascular technique; dense packing in 3D images would be achieved in most patients, but the 3D images showed aneurysm often larger than those of 2D images. (authors)

[en] Ultrarapid formation of hypereutectic Al-Si alloys /Sn-51In/ hypereutectic Al-Si alloys joints was achieved within 0.2 s via an ultrasound-induced liquid phase method at 180 °C in air. Ultrasonic vibration accelerated the element inter-diffusion between aluminium and indium to induce liquid phase. The joints consisted of Si particles, an Al-In solid solution and intermetallic compounds. The migration behaviour of Si particles, which were regarded as tracers, under the influence of ultrasonic vibration was used to investigate the joint formation. As the ultrasonic vibration time increased, the shear strength of the joints increased. The existence of Sn in the interlayer considerably affected the joint shear strength by forming intermetallic compounds.

[en] The tribological performances and rolling lubrication properties of SiO₂/graphene combinations as water-based lubricant additives were evaluated using a reciprocating ball-on-plate tribometer and two-high rolling mill. The results obtained therein revealed that dispersion of the SiO₂/graphene combinations in water is conducive to the reduction of the friction coefficient and wear volume and the increase in the load-bearing capacity, which were superior to the results obtained for the graphene nanofluids or SiO₂ nanofluids separately. In the best case, the addition of 0.1 wt% nano-SiO₂ mixed with 0.4 wt% graphene in water reduced the friction coefficient by 48.5% and the wear volume by 79% compared with the addition of 0.5 wt% graphene. Transmission electron microscopy images of the SiO₂/graphene combinations additives after friction testing showed that nano-SiO₂ supports the graphene layers as pillars and prevent assembly between the graphene layers. The synergistic effect of the components considerably enhanced the SiO₂/graphene combination. Additionally, the preliminary application of the SiO₂/graphene combination nanofluids in magnesium alloy rolling effectively decreased the rolling force and improved the surface quality of sheets.

[en] Highlights: • Extrusion dies with different angles (30°, 45°, 60°, and 90°) were adopted to produce AZ31 sheets. • Different effective strain could be introduced during extrusion due to the variation in die angles. • Large difference in effective strain along normal direction formed during sheet forming when using the 45° extrusion die. • The sheet processed by 45° extrusion die showed excellent room mechanical properties. Mg-3Al-1Zn (AZ31) alloy sheets fabricated using extrusion dies with angles of 30°, 45°, 60° and 90° were investigated. Finite element method was used to analyze the effective strain distribution in AZ31 Mg alloy during extrusion. The microstructure, texture and final mechanical properties were determined and compared among various extruded AZ31 sheets. Results demonstrated that the difference of effective strain was introduced during extrusion due to the variation in die angles. In the case of the 45° extrusion die, a large difference in effective strain along normal direction could form during sheet forming, which resulted in a uniform microstructure and weak basal texture of extruded AZ31 sheet. Therefore, the sheet processed using 45° extrusion die showed lower yield strength and r-value, but higher ductility and n-value. This study suggested that optimization of extrusion die angle could be an effective method to improve the mechanical properties of AZ31 Mg alloy sheets.

[en] This paper provided an effective plastic deformation technique, asymmetric porthole die extrusion, for fabricating AZ31 magnesium alloy sheets. Three kinds of asymmetric porthole extrusion dies were designed and entitled as APE-45, APE-60 and APE-90 die in terms of asymmetric porthole die angle, respectively. The effect of different APE processes on the microstructures, texture evolutions and mechanical properties of AZ31 sheets was investigated at room temperature. For comparison, conventional extrusion (CE) and symmetric porthole die extrusion (PE) were also conducted on processing AZ31 sheets. Shear deformation induced by APE declined the grain size and promoted a broad angular distribution of basal planes in the APE sheets compared with the CE and PE sheets. Especially, the APE-90 sheet obtained finest grain size of 5.2 µm and made basal planes tilted towards the extrusion direction by ~ 21° rotation in the sheet plane. With increasing asymmetric porthole die angle, the volume fraction of recrystallized grains gradually increased, resulting in the decrease of basal pole intensity. Due to the increased activity of basal slip, APE sheets exhibited the decrease in yield strength and r-value and increase in elongation to failure, especially for the APE-90 sheet. The improved formability of the APE sheets was attributed mainly to texture weakening. The APE-90 sheet exhibited the highest index Erichsen value and improved by ~ 74% and ~ 94% compared to the CE and PE sheets, respectively. Consequently, microstructure-texture control induced by APE could enhance the room-temperature stretch formability of AZ31 sheets.

[en] In this work, Mg-3Al-1Zn/Mg-0.3Y (AZ31/W0) laminated composite sheet was successfully fabricated by porthole die extrusion. Herein, microstructures, textures and stretch formability at room temperature of the AZ31 sheet, the W0 sheet and AZ31/W0 laminated composite sheet were systematically investigated and compared. The results showed that a tiny diffusion zone of ~ 0.35 µm and crystallographic interface were observed in the AZ31/W0 interface, indicating that the AZ31/W0 laminated composite sheet had a well bonding interface. The stretch formability at room temperature of the AZ31/W0 laminated composite sheet was apparently improved by ~ 71% and ~ 20%, respectively, as compared with the AZ31 sheet and W0 sheet. The activation of more basal slip in the W0 layer of the AZ31/W0 laminated composite sheet and the formation of extensive tensile twins in the AZ31 layer, which could effectively accommodate through-thickness strain during stretch forming, were assumed to be the main contribution to the stretch formability enhancement. Therefore, the bimetal laminated composite sheet provided a new thought to achieve high stretch formability Mg alloys via the porthole die extrusion.

[en] Here, Mg-0.4 wt%Sn based alloys containing different Y contents, Mg-0.4Sn-xY (x = 0, 0.7 and 2.0 wt%) alloys, were extruded into the sheets to systemically investigate the role of Y element on the microstructure, texture and mechanical properties of extruded Mg-0.4Sn alloy. We found that, with the Y addition, the average grain size gradually was reduced and the typical basal texture was transformed into the splitting one tilted to the extrusion direction. Moreover, the evidence of low number density and rough grain boundary cracks after tension indicated the strengthening in grain boundary cohesion with the Y addition. Besides more basal slips, the activation of prismatic slip and high intergranular strain propagation capacity were observed, which efficiently accommodated the sheet strain at room temperature. Those mentioned key factors contributed to the high room-temperature ductility of Mg-0.4Sn-0.7Y sheet. However, the formation and coarsening of Sn₃Y₅ and MgSnY phases were increasingly severe with increasing the Y addition to 2.0%. Those coarse secondary phases served as crack sources during tension deteriorating the ductility of Mg-0.4Sn-2.0Y sheet at room temperature. Therefore, we concluded that Y micro-alloying provided a new insight to achieve a superior room-temperature ductility of Mg-0.4Sn sheet.

[en] In order to develop new magnesium alloy sheets with a good balance between ductility and stretch formability at room temperature, here we designed an Mg alloy with dilute Sn and Y and investigated the microstructure, texture, mechanical properties and stretch formability of Mg-0.4Sn-0.7Y in wt% (TW00) alloy compared with AZ31 alloy under extrusion and hot rolling-annealing conditions. We found that, after extrusion, the extruded TW00 (TW00-E) sheet exhibited a more homogeneous complete dynamic recrystallized microstructure and a splitting texture character with ~$\pm$20° tilted to the extrusion direction, compared with the extruded AZ31 (AZ31-E) sheet. After hot rolling-annealing at 400 °C, both the hot rolled annealed TW00 (TW00-RA-400) and AZ31 (AZ31-RA-400) sheets presented similar complete static recrystallized microstructures. However, significant texture weakening occurred in the TW00-RA-400 sheet rather than the AZ31-RA-400 sheet, due to static recrystallization induced by twins and grain boundaries. Tensile tests revealed that the TW00-E and TW00-RA-400 sheets with high Schmid factor (SF) for basal slip exhibited high ductility (~ 33% and ~ 32%). Simultaneously, prismatic slip and texture weakening played a significant role on decreasing r-values for the TW00-E and TW00-RA-400 sheets, respectively, which contributed to the improvement in stretch formability (~ 6.2 mm and ~ 5.4 mm) at room temperature. Therefore, we concluded that the TW00 alloy provided a bright prospect to achieve a good balance between the ductility and stretch formability at room temperature via extrusion or hot rolling-annealing.

[en] A novel extrusion process, namely, slope extrusion (SE), was proposed to produce Mg–3Al–1Zn alloy sheet, thereby tailoring the strong basal texture of conventional extruded (CE) sheet. The grain morphology and texture were examined, and the tensile tests were performed along 0°, 45°, and 90° with extrusion direction. Moreover, the finite element simulation was performed to have a better understanding on the extrusion processes. An elongated weak double-peak texture titled from extrusion direction to transverse direction about 48° was obtained for the SE sheet and meanwhile the two peaks titled away from normal direction by ~ 35°. Therefore, the SE sheet showed lower yield strength and higher ductility compared with CE sheet. Especially, in terms of the transverse direction specimen of the SE sheet, the ductility reached 27.3%, which was considered as an excellent value for the wrought AZ31 sheet.