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Ti is regarded as one of the promising grain refiners in cast Al-Li-Cu alloys, but few research works have been done on its independent role. In this study, the effect of Ti on the microstructure evolution and mechanical properties of cast Al-2Li-2Cu-0.5Mg base alloy was investigated. The results revealed that the grains can be prominently refined with the increase of Ti addition. After adding Ti, high density TiB2-Al3Ti composite particles with a low lattice misfit form as heterogeneous nucleation sites for the α-Al matrix. δ'(Al3Li) and T1(Al2CuLi) precipitates that provide enhanced strength are dominated in the alloys after T6 aging treatment. The average size of both δ' and half-width of δ'-precipitation free zone (PFZ) decreases gradually with the increase of Ti content. This is because the higher binding energy between Ti atoms and vacancies limits the diffusion efficiency of Li atoms, and thus results in a higher ductility. Additionally, no nano-sized Al3Ti or core-shell structure of Al3(Li, Ti) particles are found. The tensile property test results indicate that the Al-2Li-2Cu-0.5Mg alloy achieves optimal properties after aging at 175 °C for 32 h when 0.15wt.% Ti is added. It exhibits a yield strength of 352±5 MPa, an ultimate tensile strength of 423±6 MPa, and an elongation of (3±0.4)%. These findings are expected to offer a reliable theoretical guidance for the industrial composition design of the Al-Li-Cu series cast alloys. [ABSTRACT FROM AUTHOR]

Mg–3.0Y–2.5Nd–1.0Gd–xZn–0.5Zr (x 5 0, 0.2, 0.5, and 1.0) (wt%) alloys were produced by metallic and sand mold casting to study the microstructure and mechanical properties of the alloys. The as-cast Zn-free alloys consist of a-Mg and eutectics, whereas the Zn-containing alloys contain additional long-period stacking ordered (LPSO) structures. With a higher solidification, the cooling rate brought by metallic mold casting, grains, and eutectics are refined, which enhances the elongation of the alloys, accompanied by a decrease of area fraction of the LPSO structure. Some residual eutectics in the Mg–3.0Y–2.5Nd–1.0Gd–1.0Zn–0.5Zr alloys act as obstacles to grain boundary migration during solution treatment, which make the average grain size 15–20 lm smaller than that of the other alloys and hence improve the elongation of the alloys. The Zn addition brings notable enhancements to mechanical properties of the alloys due to solid solution strengthening of Zn. Especially, the peak-aged Mg–3.0Y–2.5Nd–1.0Gd–0.5Zn–0.5Zr alloys perform with the highest overall tensile properties. [ABSTRACT FROM AUTHOR]

The structural, elastic, electronic, and thermodynamic properties of ZrxNb1−xC alloys are investigated using the first principles method based on the density functional theory. The results show that the structural properties of ZrxNb1−xC alloys vary continuously with the increase of Zr composition. The alloy possesses both the highest shear modulus (215 GPa) and a higher bulk modulus (294 GPa), with a Zr composition of 0.21. Meanwhile, the Zr0.21 Nb0.79C alloy shows metallic conductivity based on the analysis of the density of states. In addition, the thermodynamic stability of the designed alloys is estimated using the calculated enthalpy of mixing. [ABSTRACT FROM AUTHOR]

Sn–Zn solder alloys have been considered as one of the more attractive lead-free solders since it can easily replace Sn–Pb eutectic alloy without increasing the soldering temperature. However, there are still some problems to be resolved, such as the argument about the poor oxidation resistance and embrittlement behavior. In order to overcome these drawbacks, and further enhance the properties of Sn–Zn lead-free solder alloys, a small amount of alloying elements (rare earths, Bi, Ag, Al, Ga, In, Cr, Cu, Sb, Ni, Ge) added into Sn–Zn alloys were selected by many researchers. For example, a small amount of Al, P, Bi, Ga can improve the high-temperature oxidation resistance of Sn–Zn solders remarkably as well as Cr. This paper summarizes the effects of alloying elements on the wettability, oxidation resistance, melting behavior, mechanical properties, creep properties, microstructures and intermetallic compounds layer of Sn–Zn lead-free solders. [ABSTRACT FROM AUTHOR]

In order to further enhance the properties of lead-free solder alloys such as SnAgCu, SnAg, SnCu and SnZn, trace amount of rare earths were selected by lots of researchers as alloys addition into these alloys. The enhancement include better wettability, physical properties, creep strength and tensile strength. For Sn3.8Ag0.7Cu bearing rare earths, when the rare earths were La and Ce, the creep-rupture life of solder joints can be remarkably improved, nine times more than that of the original Sn3.8Ag0.7Cu solder joints at room temperature. In addition, creep-rupture lifetime of RE-doped solders increases by over four times for SnAg and seven times for SnCu. This paper summarizes the effects of rare earths on the wettability, mechanical properties, physical behavior and microstructure of a series of lead-free solders. [ABSTRACT FROM AUTHOR]

The effects of low frequency electromagnetic stirring (LFEMS) including applied voltage, rotational frequency and cooling rate on the microstructure of semisolid slurry of the Mg-2.5Gd-1Zn (at.%) alloy have been investigated. The applied voltage, rotational frequency and cooling rate all have a remarkable influence on the microstructures of the slurries. The LFEMS treatment leads to the morphology of primary Mg particles evolved from dendritic to non-dendritic. The increase of applied voltage leads to refined primary Mg particles, while the increase in rotational frequency makes the α-Mg particles initially refined and then coarsened. The decrease of cooling rate also leads to refinement of primary Mg particles. The optimal processing parameters for the fabrication of semisolid slurry are found to be: applied voltage 300-350 V, rotational frequency 15-20 Hz and cooling rate below 1.4 K/min. Under the optimized parameters, fine and spherical primary Mg particles were obtained, and the average particle size is refined from ~ 680 to ~ 150 μm. [ABSTRACT FROM AUTHOR]