Papers by Author: Jie He

Abstract: The binary Cu-Fe system is characterized by a metastable liquid miscibility gap. WhenZr is added into the Cu-Fe alloy, the miscibility gap can be extended into Cu-Fe-Zr ternary system. In the present study Cu-Fe-Zr alloys were prepared by single-roller melting-spinning method, and the samples were characterized by the SEM, EDS, HRTEM and nanoidentation. The results show that liquid-liquid phase separation into CuZr-rich and FeZr-rich liquids takes place during rapid cooling the Cu-Fe-Zr alloy, and the mechanism depends on the atomic ratio of Cu to Fe. With increasing Zr content, the size of secondary phase formed by the liquid-liquid phase separation reduces to nanoscale. The structure with amorphous Cu-rich nanoparticles embedded in the amorphous Fe-rich matrix was obtained in the as-quenched Cu₂₀Fe₂₀Zr₆₀ alloy. For its structure particularity of the Cu₂₀Fe₂₀Zr₆₀ sample, mechanical evaluation was carried out by using nanoindentation.

Abstract: The pyrolysis experiment was carried out on the waste printed circuit boards (WPCBs) of mobile phones to obtain the mixed metals which contains more than ten valuable metals. The main components in the mixed metals are elements Fe, Cu, Pb, Sn. The liquid-liquid phase separation behavior of (Fe_0.4Cu_0.6)_100-xPb_x ternary alloy has been studied. The introduction of Pb into the metastable immiscible Fe-Cu alloy can result in a stable liquid-liquid phase separation into L(Fe) and L(Cu,Pb) liquids. With the increasing of Pb content, the second phase separation in the residual L(Cu,Pb) liquid was detected, resulting in the formation of three-zone-separation structure. On this basis, a hierarchical separation system was designed to recycle mixed metals in super gravity field. The results show that the metals Cr, Co, Ni, Si are mainly enriched in the Fe-rich zone, the precious metals Au, Ag and a small amount of Zn are concentrated in the Cu-rich zone, while the low-melting-point metals Sn, Bi, Cd, and In are collected in the Pb-rich zone.

Abstract: Development of liquid-phase separated bulk metallic glasses is retarded due to difficulties in finding of immiscible systems with high glass-forming ability (GFA) of coexistent liquids. Zr-Ce alloy is a typical liquid immiscible system characterized by a liquid miscibility gap. We added Co and Cu into the Zr-Ce immiscible system and optimized the composition of the designed Zr-Ce-Co-Cu immiscible alloys. The solidification experiments were carried out for the quaternary alloys. The result indicates that the melt separated into ZrCo-rich and CeCu-rich liquids upon cooling through the miscibility gap. By optimizing the relative atomic ratio of Co:Cu, the coexistent ZrCo-rich and CeCu-rich liquids automatically assembled eutectic compositions during the liquid-liquid phase separation (LLPS). Under the condition of fast quenching, the two liquids subsequently undergo liquid-to-glass transition, resulting in the formation of composite structure with two glasses in the samples. We successfully developed phased-separated metallic glasses based on the Zr-Ce-Co-Cu immiscible alloys. This work not only strengthens the understanding in the LLPS but also provides a new strategy on the design of the dual glassy composites.

Abstract: The solidification characteristics of the immiscible alloys exhibit a unique opportunity in designing composites with spherical crystalline particles dispersed in the amorphous metal matrix. The multicomponent Al82.87Pb2.5Ni4.88Y7.8Co1.95 immiscible alloy has been designed. The ribbon samples of the multicomponent alloy were prepared by the rapid quenching. The microstructure was characterized and the phase constitution and transformation were studied. The as-quenched samples revealed the Al-based metallic glass matrix is embedded by the spherical crystalline Pb-rich particles. A method has been developed, based on the mechanism of the liquid-liquid phase decomposition in the miscibility gap of the multicomponent immiscible alloy, to produce spherical crystalline particles in the amorphous matrix. The microstructure evolution in the Al-based amorphous matrix composites has been discussed