Influence of Casting Route on the Microstructure and Mechanical Behavior of A360 Aluminum Alloy: A Process–Structure–Property Correlation

Öz

This study comprehensively examines the effect of casting route—sand versus permanent mold—on the microstructural evolution and mechanical performance of A360 aluminum alloy produced under identical alloy composition. The objective was to elucidate how differences in cooling rate and solidification kinetics affect dendritic morphology, eutectic silicon distribution, and the resulting property–structure correlation. The alloy was melted at 730 ± 5 °C under an argon-protected atmosphere and cast using silica–bentonite sand and preheated steel molds (200 °C) under gravity conditions to ensure reproducibility. Optical microscopy revealed that the permanent mold route generated a highly refined α-Al dendritic structure with reduced secondary dendrite arm spacing (SDAS) and a uniformly dispersed eutectic Si network, whereas the sand cast alloy exhibited coarse dendrites and irregular Si clusters. These microstructural distinctions led to clear performance differences: the permanent mold alloy achieved approximately 18 % higher Brinell hardness and 10–15 % higher tensile strength while maintaining comparable elongation. Furthermore, its Charpy impact energy increased from 4.81 J to 5.07 J, reflecting superior energy absorption and fracture toughness due to finer and more homogeneous solidification morphology. The findings emphasize that controlling the casting process—specifically through enhanced cooling rate—can significantly strengthen A360 alloy without any chemical modification or heat treatment. This study provides fundamental insight into the process–structure–property relationship and offers a practical reference for sustainable design and manufacturing of high-integrity aluminum components for automotive and aerospace applications.

Anahtar Kelimeler

• A360 aluminum alloy
• hardness
• impact energy
• microstructure
• permanent mold casting
• sand mold casting
• tensile strength

Kalıp Tipinin A360 Alüminyum Alaşımının Mikroyapı ve Mekanik Davranışı Üzerindeki Etkisi: Süreç–Yapı–Özellik İlişkisi

Öz

Bu çalışma, kimyasal bileşimi aynı tutulan A360 alüminyum alaşımında, farklı döküm yöntemlerinin—kum kalıba ve kokil kalıba döküm—mikroyapısal evrim ve mekanik özellikler üzerindeki etkisini kapsamlı biçimde incelemiştir. Çalışmanın temel amacı, soğuma hızı ve katılaşma kinetiğindeki farklılıkların dendrit morfolojisi, ötektik silisyum dağılımı ve buna bağlı olarak oluşan yapı–özellik ilişkisi üzerindeki etkilerini ortaya koymaktır. Alaşım, 730 ± 5 °C’de argon atmosferi altında ergitilmiş ve karşılaştırılabilir deney koşullarını sağlamak amacıyla silika–bentonit esaslı kum kalıplar ile 200 °C’de ön ısıtılmış çelik kokil kalıplara yerçekimi yöntemiyle dökülmüştür. Optik mikroskop analizleri, kokil kalıba döküm yöntemiyle elde edilen numunelerde daha ince α-Al dendritleri, azalmış ikincil dendrit kol aralığı (SDAS) ve daha homojen dağılmış ötektik Si ağı yapısının oluştuğunu; buna karşın kum kalıba döküm numunelerinde daha kaba dendritik yapı ve düzensiz Si kümelenmeleri gözlendiğini ortaya koymuştur. Bu mikroyapısal farklılıklar, mekanik özelliklerde belirgin farklılıklar yaratmıştır: kokil kalıba döküm yöntemiyle üretilen alaşım, Brinell sertliğinde yaklaşık %18 ve çekme dayanımında %10–15 oranında artış göstermiştir. Ayrıca darbe enerjisi 4,81 J’den 5,07 J’ye yükselmiş olup, bu artış daha ince ve homojen bir katılaşma yapısına bağlı olarak gelişen daha yüksek enerji soğurma ve kırılma tokluğunu yansıtmaktadır. Elde edilen sonuçlar, döküm sürecinin kontrol edilmesinin—özellikle soğuma hızının artırılmasının—herhangi bir kimyasal modifikasyon veya ısıl işlem uygulanmadan A360 alaşımının mukavemetini önemli ölçüde artırabileceğini göstermektedir. Bu çalışma, süreç–yapı–özellik ilişkisine dair temel bir bilimsel bakış açısı sunmakta ve yüksek bütünlüğe sahip alüminyum bileşenlerin otomotiv ve havacılık uygulamaları için sürdürülebilir üretim tasarımlarına pratik bir referans oluşturmaktadır.

Anahtar Kelimeler

• A360 alüminyum alaşımı
• çekme dayanımı
• darbe enerjisi
• mikroyapı
• kokil kalıp döküm
• kum kalıp döküm
• sertlik

Kaynakça

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