[Influence of casting temperature on mechanical properties of castings]

The influence of the different casting conditions on mechanical properties of castings was investigated for two kinds of Ni-Cr alloys, pure gold and pure silver by means of tensile strength tests, fractography, microstructural observation and EPMA. The casting rates of Ni-Cr alloy castings increased as the casting temperature increased. On the other hand mechanical properties worsened as the casting temperature increased. The same phenomena were observed in the case of pure gold and pure silver. These worsened mechanical properties seemed to be caused by a decrease of intergranular coherence and an increase of porosity in the Ni-Cr alloys and pure silver. Furthermore, in the case of pure silver, identical causes were responsible for the worsened mechanical properties following the rise in casting pressure and mold temperature. But in the case of pure gold, worsened mechanical properties seemed to be caused by the growth in grain size. Therefore, the best mechanical properties were obtained when the controlled temperature was at the liquid point or at the melting point.