The Copper-Arsenic Eutectic and the Cu3As Phase

In ancient bronze ingots Cu3As was observed beside other impurities like Sb. Moreover, the Cu-As bronzes were studied concerning the decrease in As during melting respectively remelting. To verify the microstructure and hardness of the eutectic and Cu3As phase appropriate mixtures were produced by melting pure Cu and As. The eutectic point in the Cu-As system is at 685 °C and 20.8 wt. % As and the Cu3As phase with 29.56 wt. % As melts at 827 °C. In the sample´s core the microstructure is a homogeneous eutectic, but near the surface it becomes hypoeutectic, i.e. an As loss took place. The lamella thickness of the eutectic was in the range of about 1 µm. The sample with a Cu3As composition showed a proeutectic microstructure with mainly Cu3As and a small amount of eutectic. In the large Cu3As crystals twin lamellae were observed. Additionally, by Vickers indents new twins were introduced. The microhardness of the Cu-As solid solution is 78 HV0.025, of the eutectic 125 HV0.025 and of the Cu3As phase 158 HV0.025. On some surfaces of the Cu3As sample a Cu-rich phase was observed. We are not able to explain this phenomenon, but it is definitively no “inverse segregation”.

Microstructure and Properties of As-Cast Cu-20Ni-5Sn Alloy

Cu-20Ni-5Sn alloy has not only high content of Ni melted point 1453°C, but also low melting point elements of Sn melted at 231.9°C, therefore, the grain structure of alloy as-cast is in perfect dendrite that lends to form segregation and inverse segregation of Sn, so that the hot rolling (cogging) processing is restricted. The influence of casting methods, cooling rate and heat treatment on the microstructures and properties of as-cast Cu-20Ni-5Sn alloy were investigated. The results show that, compared to the ingot casted in iron mold and graphite mold, the microstructure of Cu-20Ni-5Sn ingot prepared by horizontal continuous casting is the finest and the Sn segregation level is in lowest. The microstructure of the ingot casted in graphite mold is in the most perfected dendritic and with the highest segregation of Sn, the microstructure of ingot in iron molding is in the middle. The ingots must be homogenized before cold-processing. Homogenization treatment can eliminate Sn segregation and dissolve the non-equilibrium phase of ingots.

Influence of Low Frequency Electromagnetic Field on the As-Cast Structure of Cu-10%Sn-2%Zn Alloys

In this paper, the effect of low frequency electromagnetic field on the as-cast structure of Cu-10%Sn-2%Zn alloys and inverse segregation of Sn had been investigated. It is found that macrostructure and δ phase was refined, columnar-to-equiaxed transition was promoted, and inverse segregation of Sn was inhibited by applying electromagnetic field during the solidification of Cu-10%Sn-2%Zn alloys. The width of eutectoid structure (α-Cu+δ) becomes smaller, and the morphology of eutectoid δ changes from coarse acicular and massive shape to fine dotlike shape. The above mentioned effects become more obvious with the increasing of current intensity.

Influence of Electromagnetic Field on the Solidification Structure of C90500 Tin Bronze

The effect of electromagnetic field on the solidification structure of C90500 tin bronze (Cu-10%Sn-2%Zn in mass%) had been investigated in this paper. The results show that applying electromagnetic field during the solidification of C90500 tin bronze can refine macrostructure and δ phase, promote columnar-to-equiaxed transition, inhibit inverse segregation of Sn, and make the dendrite degenerate. The width of eutectoid structure (α-Cu+δ) becomes smaller, and the morphology of eutectoid δ changes from coarse acicular and massive shape to fine dotlike shape. The above mentioned effects become more obvious with the increasing of current intensity.

New Billet Mould Casting Technology

The aluminum billet casting industry is continually looking for reliable, simple and efficient ways to produce high quality, aluminum billet stock for the extrusion and forging industry. Current demands for billet quality requires that the billet have a very thin inverse segregation of less than 250 microns, uniform cell size of less than 30 microns depending on the alloy, average grain size of less than 130 microns, dendrite arm spacing of less than 50 microns and is crack free. The characteristics of the mould technology needed to achieve the required metallurgical quality economically are described in this paper.