Tailoring heat-resistant phases with strengthening effects by compound additions of zirconium, yttrium and silicon in dilute Al-Sc-(Zr)-(Y)-(Si) alloys

Abstract

Heat resistance aluminum alloys serving within 300–400 °C temperature range are prominently required due to lightweight design and extreme serve condition in aerospace and military fields. Dispersoid particles precipitated in Al–Sc system alloys possess preferential thermal stability, however, unsatisfying control of precipitate size and volume fraction may lead to low strength, limiting the possibility of further application. Here we propose a multi-component micro-alloying strategy to facilitate fine and high-density (Al,Si)3(Sc,Zr,Y) particles in Al-Sc-Zr-Y-Si alloys to obtain a small precipitate size range of 2.5–7.4 nm, a large number density of 3.30 × 1013mm−3 and a high volume fraction of 0.83 %, enabling the alloy reach an room temperature tensile strength of 180 MPa as well as an excellent heat exposure resistance performance with a loss of strength less than 5 % after exposure at 400 °C for 100h. The formed (Al,Si)3(Sc,Zr,Y) particle is coherent with the matrix and possesses a shell of Zr atom and a core containing most Sc atom and small amounts of Y and Si atoms, the precipitation is dramatically promoted by formation energy reduction from the substitution of Y for Sc and Zr atoms and Si for Al atoms during precipitation formation.

Keywords

• Al-Sc-Zr-Y-Si alloy
• Compound addition
• Heat treatment
• Precipitation strengthening
• Heat exposure resistance