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A novel concept for simplification of heat treatment process in a tool steel by the addition of aluminium has been proposed in this research. The addition of 1.08 wt-% aluminium leads to an approximately fully pearlitic state, of which the cementite lamellae are largely spheroidised. Excessive addition of 1.58 wt-% aluminium would result in the formation of a large amount of δ-ferrite. These results are mainly attributed to the synthetic effect of aluminium on the driving force of pearlite transformation and the inter-spacing distance between the proeutectoid carbides. The mechanical properties' analyses show that aluminium has promising potential to substantially simplify the processing method for developing a relative low-cost mould steel without the concomitant mechanical properties' reductions. [ABSTRACT FROM AUTHOR]

A new empirical rule to form single phase solid solution structured high entropy alloys was proposed by integrating three dependent parameters, i.e. atomic size difference δ, mixing enthalpy ΔHmix and valence electron concentration VEC. It was found that the single phase face centred cubic solid solution will form if δ<4.27%, -7.27 kJ mol-1<ΔHmix<4kJ mol-1 and VEC>8, while the single phase body centred cubic solid solution will form in the case of δ<4.27%, -7.27 kJ mol-1<ΔHmix<4 kJ mol-1 and VEC<6.87. This empirical rule was verified by typical high entropy alloys that have been reported. [ABSTRACT FROM AUTHOR]

A direct chill semicontinuous casting process to prepare 2024/3003 clad slab has been developed in the present study. Microstructure, solute distribution and bonding strength of the interfacial regions of clad slab were investigated by methods of metallographic examination, electron probe microanalysis and tensile tests. The results show that an excellent metallurgical bonding between the two different alloys can be achieved with optimal parameters. The 3003 alloy, which was poured into the mould earlier, serves as the substrate of heterogeneous nucleation of 2024 alloy. The Cu and Mg atoms diffuse from the 2024 side into the matrix of 3003 side, while Mn atoms diffuse in the opposite direction. The mean tensile strength of clad slab is 118 MPa, and the strength of the interface is higher than that of 3003 alloy. [ABSTRACT FROM AUTHOR]

The cladding hollow billet of Al-1 wt-%Mn and Al-10 wt-%Si alloys was prepared by horizontal electromagnetic continuous casting. Microstructures, composition distribution and microhardness of the interface were investigated. The results show that the ingot combines the external and internal layers by excellent metallurgical bonding without mixing. Si and Mn atoms mutually diffuse in the interfacial region between the two alloys, and the diffusion distance of the former is longer than that of the latter. In addition, a lot of tiny particles that are identified to be the intermetallic compound Al12(FeMn)3 Si are observed near the interface. [ABSTRACT FROM AUTHOR]

The cooling slope process is a simple method to produce feedstock materials for semisolid processing. In this work, the influence of surface coating of the cooling slope on grain morphology was examined. The investigation showed that the coating on the surface of the slope can affect the forming of both the solidification shell and the morphology of α-Al phase. A zebra form coating was proposed and tested, which cannot only reduce the solidification shell but also improve the grain microstructure. [ABSTRACT FROM AUTHOR]

As an improved directional solidification (DS) method, the complex directional solidification (CDS) method is used for purifying and preparing multicrystalline silicon ingot in this experiment. The induced electromagnetic field is imposed to control refining and solidification process. An integral silicon ingot with the diameter of 130 mm, the length of 130 mm and the weight of 4 kg is successfully fabricated in a self-designed CDS furnace. Metallographic analyses reveal that the direction of the most grains is parallel to the axial of silicon ingot. Analyses proved that the distribution of impurities in the cross-section is more homogeneously, the distribution in axial is improved and the effective length of silicon ingot is increased. Theoretical calculations indicate that the effect of solidified rate on the removal of impurities is limited and the impurities can be removed effectively after more than two times directional solidification process. [ABSTRACT FROM AUTHOR]