The impact of HIP process and heat treatment on the mechanical behavior of an Al-Si-Mg alloy component

• Castings generally contain pores and defects that can have a detrimental impact on mechanical properties. The hot isostatic pressing (HIP) process is usually applied to reduce internal porosities, which improves the mechanical properties because of the closed porosities. Therefore, this study investigates the effect of the HIP process on the mechanical properties of sand casting A356 aluminum alloys. This investigation was performed in collaboration with Unnaryd Modell, Quintus Technologies, and IAC Ankarsrum. Investigation of the complex interaction between the microstructural features on mechanical properties before and after the HIP process was examined using computed tomography scanning, in-situ cyclic testing, and scanning electron microscope. In the absence of large defects, the fatigue performance was improved. However, a significant variation in the result was found between the different conditions, whereas the coarser microstructure with larger porosities before the HIP process showed decreased ultimate tensile strength and elongation to failure. The samples tested under high cycle fatigue showed a reduced fatigue propagation zone in that the coarser microstructure. Moreover, large cleavage areas containing oxides in the fracture surfaces indicated that the HIP process closes all the porosities, but the oxide films are not creating a strong bonding. Furthermore, the samples tested under low cycle fatigue showed a difference in the crack propagation, whereas the coarser microstructure showed large cracks opened up away from the notch that assists the propagation leading to reduced fatigue life.

Ämnesord

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

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

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