Composites and Alloys Based on the Al-Ce System

Abstract

Aluminum alloys containing small amounts of cerium have been investigated to improve the grain refining, casting characteristics, and mechanical properties of aluminum alloys. These additions were usually made at levels of 1% or less but did not produce appreciable improvements. Recent work has shown that additions between 4% and the approximate eutectic composition of 10% improve the high-temperature performance of aluminum alloys. Corrosion performance of aluminum alloys can also be improved through the addition of Ce. Traditional aluminum alloying elements such as magnesium and silicon can be used to control casting characteristics and thermal and physical properties. Cerium oxide is the predominate oxide in rare earth mining. Much of it is discarded after separation from the heavy rare earth oxides containing Nd and Dy. The beneficial use of Ce should reduce the cost of the more desirable rare earths. Results of using Ce as an addition to aluminum in multiple manufacturing methods such as additive manufacturing, extrusion, and casting are explored. The results show significant strengthening and improved mechanical property retention at higher temperatures than in other aluminum alloys and, in some compositions, show complete recovery of mechanical properties at room temperature when exposed to elevated temperatures as high as 500°C for 1000 hours.

Microstructure Control of Al-Ce Alloys:‎ A Review

“…The microstructures of this alloy system are typically presented in Fig. 2 [10]. The as-cast microstructure reveals a pure Al phase and an extremely fine interlinked eutectic structure.…”

“…At higher temperatures, these structures remain stable. The insoluble nature of cerium in the aluminum matrix traps the intermetallic making the system unable to minimize surface energy through diffusion due to this trapping and preventing the alloy to experience a conventional coarsening interaction [10,11]. Based on the structure-property relationship, Fig.…”

“…The elevated temperature strength of Al-10Mg-8Ce is much higher than that of common aluminum piston alloys used at elevated temperatures, such as 2618-T61 (Al-2.3Cu-1.6Mg-1.1Fe-1.1Ni, wt.%), which has an ultimate tensile strength (UTS) of 90 and 52 MPa at 260 and 315 o C, respectively [10]. The strength of Al-10Mg-8Ce is comparable to that of the commercial alloy A319-T7 (Al-8.6Si-3.8Cu-0.36Mg-0.5Fe-0.3Mn, wt.%) used in engine blocks, whose ambient temperature UTS decreases from 295 to 162 MPa at 275 o C [11,12].…”

Solidification Processing of Al-Ce Alloys for High-Temperature Applications

“…In another study [9], an Al-16Ce-8Ni alloy showed a microstructure that contained finely dispersed and spheroidized Al4Ce and Al3Ni eutectic particles after annealing at 450 °C. Due to these highly stable intermetallic particles, several works on the Al-Ce alloys [10] reported remarkably high-temperature mechanical property retention compared to the other commercial Al alloys.…”

“…This ability is due to the thermally stable intermetallic phases that form. In the work of Belov and Khvan [8] on Al-Ce-Cu system, it was detected that Al and CeCu 4 Al 8 (eutectic) phases do not grow with heating and are capable of fragmenting to a maximum size of 1-2 µm after being annealed to 590 • C. In another study [9], an Al-16Ce-8Ni alloy showed a microstructure that contained finely dispersed and spheroidized Al 4 Ce and Al 3 Ni eutectic particles after annealing at 450 • C. Due to these highly stable intermetallic particles, several works on the Al-Ce alloys [10] reported remarkably high-temperature mechanical property retention compared to the other commercial Al alloys.…”