Impression relaxation and creep behavior of Al/SiC nanocomposite

Abstract

In the present study, Al-4 % of volume fractions of SiC composites were produced by mechanical alloying and the powders were gradually compacted at a pressure of 620 MPa. The post-compaction samples were sintered under an argon atmosphere at 873 K and the corresponding creep results were obtained from impression-relaxation. Additionally, compression techniques were investigated at high temperature (723 K). Enforcement rates of 8.3 × 10 -3 and 0.83 × 10 -3 mm s -1 and indenter depths of 0.5 mm and 0.8 mm were selected. Results showed a constant relation between stress relaxation and compression creep rate. Under different conditions of impression-relaxation this constant was 1000 for compression stress of 30 MPa and 32.5 MPa, and 400 for compression stress of 35 MPa, subsequently. This coefficient was affected by the porosity and was stable for different indenter depths and enforcement rates. The variations in the steady state relaxation rate were reasonable because of different nano-SiC distributions and porosities in the form of drops. Moreover, in spite of the enforcement rate decrease, the nanosized reinforcing particles caused a decrease of the relaxation rate. It should be mentioned that the constant coefficient calculated will be useful to estimate the fracture time which uses the strain rate calculated from impression-relaxation in industrial applications. Keywords: Al-SiC, creep, impression relaxation, nanocomposite, powder processing V {tudiji so bili izdelani kompoziti Al-4 % volumenskega dele`a SiC z mehanskim legiranjem, prahovi pa so bili postopoma stisnjeni do tlaka 620 MPa. Stisnjeni vzorci so bili nato sintrani v atmosferi argona na 873 K. Iz sprostitve pri vtiskovanju je bila dobljena povezava z rezultati lezenja. Dodatno so bile preiskovane tehnike stiskanja pri visoki temperaturi (723 K). Izbrani sta bili hitrosti vtiskovanja 8,3 × 10 -3 mm s -1 kot tudi 0,83 × 10 -3 mm s -1 pri globini vtiska 0,5 mm in 0,8 mm. Rezultati so pokazali konstanten koeficient med sprostitvijo napetosti in hitrostjo lezenja pri tla~enju. Vrednost konstante je bila pri razli~nih pogojih sprostitve vtiska 1000 pri napetostih stiskanja 30 MPa, 32,5 MPa in 400 pri napetosti stiskanja 35 MPa. Na koeficient vpliva tudi poroznost, stabilen pa je pri razli~nih globinah vtisa in hitrostih vtiskovanja. Tudi rezultati sprostitve so bili ob~utljivi zaradi razli~ne razporeditve SiC nanodelcev in poroznosti v obliki kapljic. Poleg tega, kljub zmanj{evanju hitrosti vtiskovanja, nanoutrjevalci zmanj{ajo hitrost sprostitve. Pomembno je omeniti, da bo iz hitrosti obremenjevanja in spro{~anja pri vtiskovanju izra~unani konstantni koeficient uporaben za napovedovanje~asa poru{itve pri industrijski uporabi. Klju~ne besede: Al-SiC, lezenje, sprostitev pri vtiskovanju, nanokompozit, obdelava prahu

Creep and mechanical properties of aluminium A356 composites reinforced with coated and un-coated MWCNTs fabricated using the stir casting method

“…However, there was no considerable advantage in adding nano SiC particles to the aluminium matrix at high creep rates. Similar studies have been performed on the creep properties of aluminium composites reinforced with SiC nanoparticles [2-4], Al 2 O 3 nanoparticles [5], boron carbide nanoparticles [6,7], and carbon nanotubes [8-11].…”

Temperature Effect on Creep and Fracture Behaviors of Nano-SiO2-composite and AlSi12Cu3Ni2MgFe Aluminum Alloy

“…Their results demonstrated a good agreement with literature values. Saberi Kakhki et al [35] studied impression relaxation behaviors of Al/4%-SiC nano-composites. They showed a constant relation between the stress relaxation and the compression creep rate.…”

“…Moreover, creep properties of the nano-composite were rarely published. Different nano-particles were introduced such as CNT [33], SiC [35], TiC [37], Al2O3 and CuO [38], with the weight percentage of 1-4% [35,38]. In addition, creep behaviors of piston aluminumsilicon alloys, with and without SiO2 nano-particles, as a special case study, were experimentally studied in this research.…”