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Abstract The current chip-level Au-Sn solder production process is very complex, to simplify the process while improving the quality of the solder, Au-20Sn solder ribbon was prepared by single-roll rapid solidification technology. The microstructure evolution, composition distribution, phase composition, melting characteristics, wettability and mechanical properties of the solder were studied. The rapidly solidified Au-20Sn solder alloy consisted of a small amount of primary ζ′-Au5Sn dendrites and eutectic structure (ζ′-Au5Sn+δ-AuSn). The microstructure was refined and the components were evenly distributed, while no new phase was formed during the annealing. With Sn element diffused into the δ-AuSn phase from the ζ′-Au5Sn phase, the ζ′-Au5Sn phase was decomposed and the δ-AuSn phase grew up and distributed in the matrix. After rolling, the δ-AuSn phase was elongated along the elongation direction of the ribbon, and the elements were further segregated. Ultimately, compared to the cast-rolling Au-20Sn solder, the melting range was narrower, and the wettability and the shear strength of the solder joint improved. Highlights • Au-20Sn solder was prepared by single-roll rapid solidification technology. • The primary phase of rapidly solidified Au-20Sn was obviously refined. • The refinement mechanism of rapidly solidified Au-20Sn solder is proposed. • The primary phase completely decomposed after suitable annealing process. • The properties of rapid solidification-rolling Au-20Sn solder were improved. [ABSTRACT FROM AUTHOR]

A novel and simple method for preparing Mg–50%Al 4 C 3 (hereafter in wt.%) master alloy has been developed by powder in-situ synthesis process under argon atmosphere. X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) results show the existence of Al 4 C 3 particles in this master alloy. After adding 1.8% Mg–50%Al 4 C 3 master alloy, the average grain size of α-Mg decreased from 360 μm to 154 μm. Based on the DTA test results and calculation of the planar disregistry between Al 4 C 3 and α-Mg, Al 4 C 3 particles located in the central regions of magnesium grains can act as the heterogeneous nucleus of primary α-Mg phase. [ABSTRACT FROM AUTHOR]

Abstract: A novel Mg–50% Al4C3 (hereafter in wt.%) master alloy has been developed by powder in situ synthesis process, the role of manganese on the grain refining efficiency of AZ91D magnesium alloy refined by this master alloy has been investigated. X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS) results show the existence of Al4C3 particles in this master alloy. After addition of 0.6% Al4C3 or combined addition of 0.6% Al4C3 and 0.27% Mn, the average grain size of AZ91D decreased dramatically from 360μm to 210μm, and from 360μm to130μm, respectively. However, no further refinement of grain size was achieved with additional amount of Mn exceeding 0.27% for AZ91D alloy refined by 0.6% Al4C3 in the present investigation. Al–C–O–Mn–Fe-rich intermetallic particles with an Al–C–O-rich coating film, often observed in the central region of magnesium grains of the AZ91D alloy treated by the combination of Al4C3 and Mn, are proposed to be the potent nucleating substrates for primary α-Mg. [Copyright &y& Elsevier]

Abstract: A novel Mg–50% TiB2 master alloy has been developed by powder in situ synthesis process and its grain refining effect on AZ91D magnesium alloy has been investigated. X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS) results show the existence of TiB2 particles in this master alloy. After adding 1.8wt% this master alloy, the average grain size of AZ91D decreased markedly from about 240μm to 50μm, and the dendritic structure of the primary phase α-Mg was obviously refined. Ti and B enriched particles, often observed in the central regions of magnesium grains, are proposed to be the potent nucleating substrates for primary Mg. [Copyright &y& Elsevier]