Effects of sintering techniques and parameters on microstructure and mechanical properties of Al-15Si-2,5Cu-0.5Mg compacts and Al-15Si-2,5Cu-0.5Mg/B4C composites


Özer M., Aydoğan S. İ., Çinici H., Özer A.

MATERIALS TODAY COMMUNICATIONS, vol.30, no.5, pp.1-14, 2022 (SCI-Expanded)

  • Publication Type: Article / Article
  • Volume: 30 Issue: 5
  • Publication Date: 2022
  • Doi Number: 10.1016/j.mtcomm.2022.103192
  • Journal Name: MATERIALS TODAY COMMUNICATIONS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, INSPEC
  • Page Numbers: pp.1-14
  • Gazi University Affiliated: Yes

Abstract

In this study, Al-Si compacts and Al-Si/B4C composites were produced from hypereutectic Al-Si alloy powders by

cold pressing/conventional sintering and cold pressing/microwave sintering techniques. The effects of sintering

temperature, sintering time and B4C particle addition on microstructural properties, density, hardness and

transverse rupture strength were investigated. The phases and intermetallic compounds formed in the micro-

structure were determined by X-ray diffraction. Densities of the samples were measured by Archimedes’ tech-

nique. Macro hardness measurements were carried out with Brinell hardness test. Three-point bending tests were

applied to the samples according to ASTM-B528–16. Elemental Al regions, master alloy (Al-Si-Cu-Mg) regions,

primary Si particles and Cu- and Mg-rich secondary phases were determined in the microstructure. It was

determined that the Cu- and Mg-rich secondary phases are θ(CuAl2), β(Mg2Si), γ(Al2CuMg) phases. An increase

in porosity was determined in conventional sintered samples compared to green Al-Si specimens. In addition, it

was observed that the amount of porosity increases, grain size and primary Si grains coarse with increasing

sintering temperature in conventional sintering. The change in the amount of pores of the samples produced by

microwave sintering without holding time at the sintering temperature is not as obvious as in conventional

sintering. Similar microstructures were obtained in the samples at increasing sintering temperatures in micro-

wave sintering. In the samples produced by conventional sintering, the hardness value decreased with increasing

sintering temperature. Addition of 5 wt% B4C caused an increase in hardness at all sintering temperatures. The

addition of 10 and 15 wt% B4C caused a decrease in hardness. In microwave sintering, the general trend in

hardness change was a decrease with increasing B4C particle addition and increasing sintering time. Transverse

rupture strength values close to and similar to each other in conventional sintered samples were obtained at

different sintering temperatures. Transverse rupture strength values increased with the addition of 5 wt% B4C

particles, and decreased with the addition of 10 and 15 wt% B4C particles.