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Microstructure and mechanical properties of an extruded Mg 96 Zn 1 Y 3 alloy have been investigated in the current study. Microstructure of as extruded alloy consists of α-Mg, long period stacking ordered (LPSO) phase and parallelepiped Y-riched phases, which exhibits a bimodal distribution of fine recrystallized and coarse elongated grains. Fine recrystallized grains with an average grain size of 1.5 μm are mainly pinned by bulk LPSO-14H phase, inside which both LPSO-18R phase and LPSO-14H phase coexist. The extruded Mg 96 Zn 1 Y 3 alloy exhibits a good combination of yield strength and elongation below 200 °C, which is mainly attributed to LPSO phases, stronger texture and finer DRX grains. The main deformation is controlled by load transfer mechanism below 250 °C, and deformation is controlled by non-basal dislocation movement between 300 °C and 325 °C. A good plasticity is attained at 350 °C with an elongation of 140%. The flow stress behavior at 350 °C is mainly controlled by non-basal slip accompanying with dynamic recrystallization and growth of grain. [ABSTRACT FROM AUTHOR]

Abstract: The current work presents the room-temperature mechanical properties and the corrosion resistance in 3.5% NaCl solution of conventional casting and rapidly solidified Mg6ZnMn (ZM61) magnesium alloys. It is found that the mechanical properties of rapidly solidified ZM61 alloy are dramatically enhanced, with the ultimate strength increased from 335MPa to 460MPa (37% increment), which can be attributed to the formation of the refined dendrite microstructure and the strengthening MgZn2 phase distributed within the matrix. Furthermore, the rapidly solidified ZM61 alloy performs better in corrosion resistance than the extruded ZK60 and pure Mg alloys, suggesting that the rapid-solidification technique is a promising way to improve the strength and corrosion resistance of magnesium alloy for the structural and corrosive media utilization. [Copyright &y& Elsevier]

Abstract: A 2219-T6 aluminum alloy was underwater friction stir welded at a fixed welding speed and various rotation speeds in order to illuminate the influence of rotation speed on the performance of underwater joints. With increasing rotation speed, the hardness of the stir zone (SZ) gradually increases due to the increase in dislocation density. The tensile strength first increases from 600 to 800rpm and then reaches a plateau in a wide rotation speed range. After that a remarkable decrease in tensile strength occurs owing to the formation of void defect. The joint welded at lower rotation speed tends to be fractured in the SZ. At higher rotation speeds, the hardness increase in the SZ makes the fracture locations of defect-free joints move to the thermal-mechanically affected zone (TMAZ) or heat affected zone (HAZ). [Copyright &y& Elsevier]

Abstract: Underwater friction stir welding (underwater FSW) has been demonstrated to be available for the strength improvement of normal FSW joints. In the present study, a 2219 aluminum alloy was underwater friction stir welded at a fixed rotation speed of 800rpm and various welding speeds ranging from 50 to 200mm/min in order to clarify the effect of welding speed on the performance of underwater friction stir welded joint. The results revealed that the precipitate deterioration in the thermal mechanically affected zone and the heat affected zone is weakened with the increase of welding speed, leading to a narrowing of softening region and an increase in lowest hardness value. Tensile strength firstly increases with the welding speed but dramatically decreases at the welding speed of 200mm/min owing to the occurrence of groove defect. During tensile test, the joint welded at a lower welding speed is fractured in the heat affected zone on the retreating side. While at higher welding speed, the defect-free joint is fractured in the thermal mechanically affected zone on the advancing side. [ABSTRACT FROM AUTHOR]

As-cast Mg–5.3Zn–0.6Ca (weight percent) alloy was indirectly extruded at 300 °C with different deformation rates (ram speeds of 0.1, 0.3, 0.5 mms − 1 ), and the microstructure, texture and mechanical properties of the as-extruded alloys were investigated in the current study. With the increase of deformation rates, the average size and volume fraction of dynamic recrystallized grains were remarkably increased. The basal fiber texture became weak in the as-extruded alloy with higher volume fraction of recrystallized grains, because most of the basal planes in these grains were tilted to extrusion direction about 30–40°. The higher deformation rate decreased the tensile yield stress due to the grain coarsening and basal texture weakening, while the elongation was improved, which was resulted from the enhanced work hardening rate. [ABSTRACT FROM AUTHOR]

Inconel 718 was subjected to various heat treatments, i.e., solution heat treatment, standard ageing treatment and standard ageing plus 700 °C thermal exposure. The mechanical properties of the alloys were determined using tensile tests and Charpy pendulum impact tests at 650 °C and room temperature, respectively. The highest yield strength of 988 MPa was attained in the standard aged specimen, whereas a maximum impact toughness of 217 J cm −2 was attained in the solution-treated specimen. After thermal exposure, the mechanical properties of the specimens degrade. Both the yield strength and impact toughness decreased monotonically with increasing thermal exposure time. Subjected to a 10000-h long-term thermal exposure, the yield strength dramatically decreased to 475 MPa (almost 50% of the maximum strength), and the impact toughness reduced to only 18 J cm −2 . The microstructures of the specimens were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Coarsening of γ′ and γ″ and the transformation of γ″ to δ-Ni 3 Nb was observed after thermal exposure. However, a complete transformation from metastable γ″ to δ-Ni 3 Nb was never accomplished, even after the 10000-h long-term thermal exposure. Based on the obtained experimental results, the effects of the microstructural evolution on the mechanical properties are discussed. [ABSTRACT FROM AUTHOR]

The yield strength of the extruded Mg−9.9Y−3.7Zn (wt%) alloy at room temperature is remarkably increased from 240 MPa to 364 MPa using low-stain rolling. This significant improvement is ascribed to the combination of intensive basal texture, fine long-period stacking ordered phase particles and a high density of dislocations. The elongation of the rolled alloy increases as the strain of rolling increases, which is attributed to the homogenous distribution of fine long-period stacking ordered phases. [ABSTRACT FROM AUTHOR]

Abstract: The mechanical properties at room temperature and the corrosion behavior in simulated body fluid (PBS) at 37°C of a Ni-free Zr62.3Cu22.5Fe4.9Al6.8Ag3.5 bulk metallic glass (BMG) were investigated. This BMG exhibits a good room temperature plasticity of 8%, a yield strain of 1.9% and a high fracture strength of about 1800MPa. Interestingly, the novel Zr-rich BMG possesses a specific strength (σ/ρ) of about 280MPacm3/g higher than that of conventional biomedical Ti6Al4V alloy and 316L stainless steel. In addition, this alloy also has a high corrosion resistance with a low corrosion penetration rate in simulated body fluids (PBS). The present Ni-free Zr-rich BMG with a critical diameter above 1cm, together with the high specific strength, large plasticity and good corrosion resistance in PBS, has excellent potential in biomedical applications. [Copyright &y& Elsevier]