{"id":12209,"date":"2026-06-01T04:24:00","date_gmt":"2026-06-01T04:24:00","guid":{"rendered":"https:\/\/www.alcircle.com\/blog\/?p=12209"},"modified":"2026-06-03T10:46:13","modified_gmt":"2026-06-03T10:46:13","slug":"aluminium-alloy-discs-after-annealing","status":"publish","type":"post","link":"https:\/\/www.alcircle.com\/blog\/aluminium-alloy-discs-after-annealing","title":{"rendered":"Abnormal grain growth in 0.95 Si+Fe aluminium alloy discs after annealing obtained by continuous casting (CC) and direct chill casting (DC)"},"content":{"rendered":"\n

Abstract<\/strong><\/h2>\n\n\n\n

This study analysed the mechanism responsible for abnormal grain growth in 0.95 per cent Si+Fe aluminium alloy discs, previously cold-rolled and subjected to annealing in stationary furnaces. The discs were manufactured from raw materials obtained by two distinct casting processes: Continuous casting and Direct Chill casting. After 80 per cent cold deformation, the samples were annealed at 500\u00b0C for 15 hours and subsequently exposed to simulated thermal rework cycles. The results showed that the initial annealing did not cause abnormal grain growth in either production route. However, when the same thermal cycle was repeated as rework, the phenomenon began to occur after approximately 45 hours in the material from Direct Chill casting and after approximately 60 hours in the material from the continuous casting process. This difference in behaviour was attributed to the distinct characteristics of the second-phase particles formed in each type of casting.<\/p>\n\n\n\n

Introduction<\/strong><\/h2>\n\n\n\n

The 0.95 per cent Si+Fe alloy is widely used in the production of household utensils due to its high formability, good corrosion resistance and low density. Its manufacture can occur through both continuous casting and direct chill casting, as the alloy exhibits good fluidity and consistent behaviour under different solidification conditions. However, the occurrence of abnormal grain growth during annealing represents a critical challenge, as it compromises the surface quality and mechanical performance of stamped components.<\/p>\n\n\n\n

When poor quality becomes a problem: Fault identification & corrective actions<\/strong><\/h2>\n\n\n\n

The aluminium disc manufacturer reported that its products had been experiencing defects in the market due to the appearance of giant grains after the stamping stage, as illustrated in Figure 1. The company uses a 4.0 mm thick plate as raw material, produced by both continuous casting and direct chill casting. These plates are subsequently cold-rolled to the final thickness, cut into discs and subjected to annealing. The heat treatment adopted consists of 500\u00b0C for 15 hours.<\/p>\n\n\n\n

After annealing, the discs undergo an inspection to identify surface stains. Parts exhibiting this type of defect are segregated and sent for reworking, using the same thermal cycle. This procedure can be repeated one to four times, depending on the need.<\/p>\n\n\n\n

The defect exhibited random behaviour: It did not appear in all batches, and its occurrence varied significantly in quantity. The justification for adopting such a severe annealing cycle was the need to prevent the appearance of oil stains on the surface of the discs. This scenario motivated the present study, whose objective was to clarify the origin of the defect and identify the factors that favour abnormal grain growth.<\/p>\n\n\n

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Figure 1: The abnormal grain growth after stamping the piece<\/em><\/p>\n\n\n\n

Materials and methods<\/strong><\/h2>\n\n\n\n
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    The raw material was obtained by two industrial routes:<\/p>\n\n\n\n