Mechanism of lubrication-induced surface cracking in hot chamber die cast thin-walled AZ91D parts

• Thin-walled hot chamber die cast parts are often used to make telephone casings and similar products having primarily requirements on weight and aesthetically satisfying surfaces. The post casting surface treatment often generates a glossy appearance. The glossy appearance makes it extremely sensitive to small-scale flaws, such as blisters, cold shuts, and cracks. Hot chamber die casting of thin-walled parts requires high filling speed and the use of lubrication because the parts have high aspect ratios. In the manufacturing of such high aspect ratio parts with a wall thickness of 0.6 mm, a new type of cold crack induced by the lubrication is observed. To some extent this defect is similar to a blister, but the characteristic bump is not formed and the actual crack is formed by thermal contraction along the high aspect ratio areas.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)

Nyckelord

Aspect ratio

Crack initiation

Lubrication

Shrinkage

Surface treatment

Thickness measurement

Thin walled structures

Glossy

Hot chamber die cast

Lubrication induced surface cracking

Thermal contraction

Die castings

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