Influence of Microstructural Inhomogeneity on Fracture Behaviour in SSM-HPDC Al-Si-Cu-Fe Component with Low Si Content

Abstract:

In the current paper, a low-Si containing aluminium alloy (1.4-2.2% Si) was used to fabricate a complex shape telecom component using Semi-Solid High-Pressure Die Cast (SSM-HPDC), process. Microstructure and fracture characteristics were investigated. The cast material exhibited microstructural inhomogeneity, in particular macrosegregation in the form of liquid surface segregation bands in addition to sub-surface pore bands and gross centre porosity. Tensile specimen were taken from the cast components. Elongation and microstructural inhomogeneity were investigated and correlated. Fracture surfaces of the tensile specimen were examined under scanning electron microscope (SEM). The study showed that both near surface liquid segregation bands and subsurface porosity strongly affected the fracture behaviour. Dominant for loss of ductility were gross centre porosity. This centre porosity was found to be a combination of trapped gas and insufficient, irregular feeding patterns.

• Periodical: Solid State Phenomena (Volumes 217-218)
• Pages: 67-74
• DOI: https://doi.org/10.4028/www.scientific.net/SSP.217-218.67
• Online since: September 2014
• Authors: Mostafa Payandeh*, Anders E.W. Jarfors, Magnus Wessen
• Keywords: Defect Band, Fracture Surface, Macro Segregation, RheoMetal Process, Skin Layer, SSM HPDC, Thin-Wall Component

References

[1] M. Hitchcock, Y. Wang, Z. Fan, Secondary solidification behaviour of the Al–Si–Mg alloy prepared by the rheo-diecasting process, Acta Materialia, 55 (2007) 1589-1598.

DOI: 10.1016/j.actamat.2006.10.018

[2] Atkinson HV. Alloys for Semi-Solid Processing. Solid State Phenomena 192 (2013): 16-27.

[3] Langlais J, Chen XG, Lemieux A, Andrade N, Bucher L. The semi-solid forming of an improved AA6061 wrought aluminum alloy composition. Solid State Phenomena 141 (2008): 511-6.

DOI: 10.4028/www.scientific.net/ssp.141-143.511

[4] Kaufmann H, Uggowitzer PJ. Metallurgy and processing of high integrity light metal pressure castings: Fachverlag Schiele & Schön. (2007).

[5] Kaufmann H, Fragner W, Galovsky U, Uggowitzer P, editors. Fluctuations of alloy composition and their influence on sponge effect and fluidity of A356-NRC. Proceedings of the 2nd International Light Metals Technology Conference; (2005).

[6] Chen ZW. Skin solidification during high pressure die casting of Al–11Si–2Cu–1Fe alloy. Materials Science and Engineering: A 348 (2003): 145-53.

DOI: 10.1016/s0921-5093(02)00747-5

[7] Laukli HI, Gourlay CM, Dahle AK. Migration of crystals during the filling of semi-solid castings. Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science 36 (2005): 805-18.

DOI: 10.1007/s11661-005-0195-z

[8] Gourlay C, Dahle A, Nagira T, Nakatsuka N, Nogita K, Uesugi K, Granular deformation mechanisms in semi-solid alloys. Acta Materialia 59 (2011): 4933-43.

DOI: 10.1016/j.actamat.2011.04.038

[9] Otarawanna S, Gourlay CM, Laukli HI, Dahle AK. The thickness of defect bands in high-pressure die castings. Materials Characterization 60 (2009): 1432-41.

DOI: 10.1016/j.matchar.2009.06.016

[10] Laukli HI, Gourlay CM, Dahle AK, Lohne O. Effects of Si content on defect band formation in hypoeutectic Al-Si die castings. Materials Science and Engineering A 413-414 (2005): 92-7.

DOI: 10.1016/j.msea.2005.08.194

[11] Magnus W, Cao H, inventors; WO Patent WO/2006/062, 482, assignee. A method of and a device for producing a liquid-solid metal composition2006.

[12] Eskin DG, Suyitno, Katgerman L. Mechanical properties in the semi-solid state and hot tearing of aluminium alloys. Progress in Materials Science 49 (2004): 629-711.

DOI: 10.1016/s0079-6425(03)00037-9

[13] Gourlay C, Laukli H, Dahle A. Defect band characteristics in Mg-Al and Al-Si high-pressure die castings. Metallurgical and Materials Transactions A 38 (2007): 1833-44.

DOI: 10.1007/s11661-007-9243-1

[14] Laukli HI, Gourlay CM, Dahle AK, Lohne O. Effects of Si content on defect band formation in hypoeutectic Al–Si die castings. Materials Science and Engineering: A 413 (2005): 92-7.

DOI: 10.1016/j.msea.2005.08.194