Formation Mechanisms of Aluminum Die Castings Microstructures

• Published in: Imono Vol. 63; no. 4; pp. 347 - 352
• Main Authors: Nishi, Naomi, Komazaki, Toru, Takahashi, Yosuke
• Format: Journal Article
• Language: Japanese
• Published: Japan Foundry Engineering Society 25.04.1991
• ISSN: 0021-4396; 2186-0335
• DOI: 10.11279/imono.63.4_347

The solidification phenomena within a shot sleeve and formation mechanisms for microstructures of JIS-ADC10 alloy die castings were investigated in samples prepared an using 90 metric tonne locking force cold chamber die casting machine. The solidified structure of the as cast materials were examined by optical microscopy. Quantitative analysis of microstructure was done with color image analyzer. The microstructures of JIS-ADC10 alloy after die casting consisted of coarse α phase with dendrite arm spacing (DAS) above 10 μm, fine α phase with DAS 5 to 10 μm and fine eutectic structures. The amount of coarse α phase increased with time from pouring molten metal into the shot sleeve to injection initiation. The amount of coarse α phase increased with decreasing pouring temperature. The coarse α phase was formed in the shot sleeve and injected scatteringly into die cavity. Two other types of abnormal structures which solidified in the shot sleeve existed in the die castings microstructure in addition to the coarse α phase. The fast was a scattered structure which exhibited a planar interface with the matrix. The second was a massive structure which agglomerated coarse α phase and coarse eutectic silicon.