The effects of Mg addition on the microstructure and mechanical properties of thixoformed Al-5%Si-Cu alloys

M. S. Salleh, Mohd. Zaidi Omar, J. Syarif

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

In this study, the effects of different amounts of magnesium (Mg) on the microstructures and tensile properties of thixoformed Al-5%Si-Cu alloys were investigated. Three different alloys containing various amounts of Mg (0.5, 0.8 and 1.2 wt%) were prepared through the cooling slope casting technique, before they were thixoformed using a compression press. Several of the thixoformed samples were then treated with a T6 heat treatment, that is, solution treatment at 525 °C for 8 h, quenching in warm water at 60 °C, followed by aging at 155 °C for 4 h. All of the samples were then characterised by optical microscopy (OM), scanning electron microscopy (SEM) energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as by tensile tests. The results revealed that magnesium was able to refine the size of α-Al globules and the eutectic silicon in the samples. It was also observed that a compact π-Al9FeMg3Si5 phase was formed when the magnesium content was 0.8 wt% and 1.2 wt%. The mechanical properties of the thixoformed alloys improved significantly after the T6 heat treatment. The highest attainment was recorded by the latter alloy (i.e. with 1.2 wt%Mg) with its ultimate tensile strength (UTS) as high as 306 MPa, yield strength (YS), 264 MPa, and elongation to fracture of 1.8%. The fracture of thixoformed alloy with a low Mg content (0.5 wt%) showed a combination of dimple and cleavage fracture, whereas in the alloy that contained the highest Mg content (1.2 wt%), cleavage fracture was observed.

Original languageEnglish
Pages (from-to)121-130
Number of pages10
JournalJournal of Alloys and Compounds
Volume621
DOIs
Publication statusPublished - 15 Feb 2015

Fingerprint

Magnesium
Mechanical properties
Microstructure
Heat treatment
Silicon
Tensile properties
Eutectics
X ray diffraction analysis
Optical microscopy
Yield stress
Elongation
Quenching
Casting
Compaction
Tensile strength
Aging of materials
Cooling
Scanning electron microscopy
Water

Keywords

  • Al-Si-Cu alloy
  • Mechanical properties
  • T6 heat treatment
  • Thixoforming

ASJC Scopus subject areas

  • Mechanical Engineering
  • Mechanics of Materials
  • Materials Chemistry
  • Metals and Alloys

Cite this

The effects of Mg addition on the microstructure and mechanical properties of thixoformed Al-5%Si-Cu alloys. / Salleh, M. S.; Omar, Mohd. Zaidi; Syarif, J.

In: Journal of Alloys and Compounds, Vol. 621, 15.02.2015, p. 121-130.

Research output: Contribution to journalArticle

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abstract = "In this study, the effects of different amounts of magnesium (Mg) on the microstructures and tensile properties of thixoformed Al-5{\%}Si-Cu alloys were investigated. Three different alloys containing various amounts of Mg (0.5, 0.8 and 1.2 wt{\%}) were prepared through the cooling slope casting technique, before they were thixoformed using a compression press. Several of the thixoformed samples were then treated with a T6 heat treatment, that is, solution treatment at 525 °C for 8 h, quenching in warm water at 60 °C, followed by aging at 155 °C for 4 h. All of the samples were then characterised by optical microscopy (OM), scanning electron microscopy (SEM) energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as by tensile tests. The results revealed that magnesium was able to refine the size of α-Al globules and the eutectic silicon in the samples. It was also observed that a compact π-Al9FeMg3Si5 phase was formed when the magnesium content was 0.8 wt{\%} and 1.2 wt{\%}. The mechanical properties of the thixoformed alloys improved significantly after the T6 heat treatment. The highest attainment was recorded by the latter alloy (i.e. with 1.2 wt{\%}Mg) with its ultimate tensile strength (UTS) as high as 306 MPa, yield strength (YS), 264 MPa, and elongation to fracture of 1.8{\%}. The fracture of thixoformed alloy with a low Mg content (0.5 wt{\%}) showed a combination of dimple and cleavage fracture, whereas in the alloy that contained the highest Mg content (1.2 wt{\%}), cleavage fracture was observed.",
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