Thickness of chill zone formed on ADC 12 alloy die castings
1971; Japan Institute of Light Metals; Volume: 21; Issue: 6 Linguagem: Inglês
10.2464/jilm.21.379
ISSN1880-8018
Autores Tópico(s)Microstructure and mechanical properties
ResumoIt has been difficult to determine the chill zone formed on aluminum alloy die castings by conventional or metallographic method. This paper describes a tentative method to determine it in Al-12Si-Cu alloy (JIS ADC 12) die castings.The percentage of crystallized α-phase area rapidly increased from the surface to the depth of 0.5mm being inversely proportional to the micro-Vicker's hardness. The surface layer having micro-Vicker's hardness more than 105, corresponding the α percentage less than 60%, was defined as a chill zone.A thinner chill zone was formed on the castings having a heavy section. The thickness of chill zone on die castings of 10mm in thickness was as little as less than 50% of that in castings of 2mm in thickness. Casting factors such as metal temperature, injection pressure, gate velocity and filling ratio in the sleeve had little effects on the formation of chill zones. Only the die temperature had an effect with a significance level of 99% on the basis of variance analysis. The thickness of chill zone had a correlation to tensile strength and elongation. An inverse correlation was found, however, when the gate velocity was changed.
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