{"id":12418,"date":"2026-07-02T11:51:54","date_gmt":"2026-07-02T11:51:54","guid":{"rendered":"https:\/\/www.alcircle.com\/blog\/?p=12418"},"modified":"2026-07-02T11:51:57","modified_gmt":"2026-07-02T11:51:57","slug":"the-effect-of-inclusions-on-the-aluminium-lid-forming-process","status":"publish","type":"post","link":"https:\/\/www.alcircle.com\/blog\/the-effect-of-inclusions-on-the-aluminium-lid-forming-process","title":{"rendered":"The effect of inclusions on the aluminium lid forming process"},"content":{"rendered":"\n

This study examined the mechanism responsible for fractures occurring in the rivet region of beverage can ends manufactured from an Al\u2011Mg4.5 alloy during the forming process.<\/p>\n\n\n\n

Optical microscopy and scanning electron microscopy coupled with energy\u2011dispersive X\u2011ray spectroscopy (SEM\/EDS) revealed that the fractures were triggered by an inclusion containing Al, Ti, Ca and V. Further analysis indicated that this inclusion originated from one of the raw materials added to the alloy during casting.<\/p>\n\n\n\n

After identifying the inclusion\u2019s composition and source, the supplier was notified and conducted a traceability assessment, which uncovered a failure that had occurred during the production of specific batches. Based on this diagnosis, adjustments were implemented in the raw material manufacturing process, eliminating the formation of the unwanted inclusion. As a result, the aluminium alloy quality was restored to the level of excellence required for its intended application.<\/p>\n\n\n\n

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

In the aluminium industry, inclusions, typically non-metallic particles, under certain conditions, can lead to defects that severely compromise the integrity of thin- gauge products such as household aluminium foil, beverage and food can bodies, ends and electrical wiring. For critical applications, industrial experience demonstrates that achieving quality excellence depends on the supply of metal with a high level of cleanliness, that is, with an extremely low inclusion content.<\/p>\n\n\n\n

Although a variety of highly effective molten metal treatment technologies have been developed over the years to reduce these particles to near\u2011zero levels, occasional situations still occur in which inclusions remain trapped within the aluminium. When this happens, they may ultimately give rise to surface defects or even fractures during subsequent mechanical forming operations.<\/p>\n\n\n\n

Impact on quality<\/strong><\/h2>\n\n\n\n

Inclusions have a decisive influence on the final quality of aluminium. They may arise from several sources, including contamination from metal handling tools and equipment, reactions between molten aluminium and the environment, or inputs added during casting, such as grain refiners and alloying elements. Regardless of their origin, the consequences for manufacturing are substantial: Reduced mechanical strength, surface finish damage, failures during forming operations and higher scrap rates. For this reason, controlling their formation and ensuring their effective removal are essential steps in maintaining consistent performance and reliability in aluminium products.<\/p>\n\n\n\n

Investigating the root cause<\/strong><\/h2>\n\n\n\n

The domestic market has long produced the Al-Mg4.5 alloy to a high-quality standard; however, at a certain moment, customers began reporting failures in the rivets of the beverage can ends.<\/p>\n\n\n\n

Initial laboratory analyses indicated that the fracture was associated with an inclusion containing Al, Ti, Ca and V. Figure 1 below shows this inclusion within the fracture zone as observed via SEM, while Figure 2 presents its appearance under optical microscopy. Several lids exhibiting the same defect were examined and the same inclusion was found in all of them. Because this type of inclusion had never appeared in the company\u2019s internal records, it was classified as a previously unknown inclusion.<\/p>\n\n\n

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Figure 1: Inclusion located in the fracture region – SEM \u2013 262X magnification<\/em><\/p>\n\n\n

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Figure 2: Inclusion located near the fracture region; Optical microscopy, 50X magnification<\/em><\/p>\n\n\n\n

To determine the origin of this inclusion, a multidisciplinary team was assembled, consisting of engineers, process technicians, remelt operators, a technical assistant and a metallographic analyst with extensive SEM\/EDS experience. The investigation was guided by a classic failure analysis tool, the Ishikawa diagram.<\/p>\n\n\n\n

Defect characterisation<\/strong><\/h2>\n\n\n\n

The inclusion was characterised using both optical microscopy and SEM\/EDS.<\/p>\n\n\n\n

The inclusion\u2019s composition included the elements Al, Ti, Ca and V. Optical microscopy revealed that the particle exhibited a pale grey colour, very similar to the TiAl\u2083 phase found in the microstructure of TiAl or TiBAl grain refiners. Furthermore, no evidence of reaction or transformation of this phase was identified in the analysed material.<\/p>\n\n\n\n

Different batches of grain refiners were analysed, but the particle in question was not observed in any of them.<\/p>\n\n\n\n

A second line of investigation involved analysing another input material added to the Al-Mg4.5 alloy during the casting process. The particle was identified during the initial evaluations, although in small quantities. Based on these preliminary results, the scope of the investigation was expanded to analyse 18 batches of this input material held in stock.<\/p>\n\n\n\n

The following criterion was adopted: Number of particles per cm\u00b2.<\/p>\n\n\n\n

The results were surprising, some batches showed only 2 particles, while others contained 49, there were even batches with 250 and up to 330 particles per cm\u00b2, with sizes ranging from 50 to 220 \u00b5m.<\/p>\n\n\n\n

Corrective actions: Restoring aluminium quality<\/strong><\/h2>\n\n\n\n