چكيده به لاتين
Nowadays, magnesium-zinc-calcium alloys have attracted the attention of the medical industries due to their biodegradability and properties close to the properties of bone, including elastic modulus and strength. Melting and casting processes are among the manufacturing processes of these alloys. In melting and casting processes, quality of the cast part and the final properties are strongly influenced by solidification condition. Therefore, thermal analysis method has been used to investigate solidification characteristics of the alloys. For this purpose, the cooling curve of four alloys Mg-3Zn, ZX301, ZX303 and ZX306 have been plotted in four different cooling rates. The effect of cooling rate and calcium content on the solidification characteristics of these alloys has been investigated.
The results showed that variation of cooling rate and calcium percentage affected nucleation and growth characteristics of primary dendrites, solidification range and solidus temperature, solid fraction curve, coherency point of dendrites and the characteristic of the eutectic reaction. Increasing the cooling rate increased the nucleation temperature of primary dendrite, the nucleation under cooling, the solidification range; and decreased the nucleation temperature of eutectic phases, the solidus temperature, the dendrite coherency temperature and time, the solid fraction at dendrite coherency point.
Then, solid fraction at dendrite coherency point increased at high cooling rates and caused a sharp decrease in hot cracking susceptibility. Also, by increasing the percentage of calcium content, it reduced the nucleation temperature of primary dendrites, temperature and time of dendrite coherency; and increased the nucleation temperature of the eutectic phases.
