Mechanical behavior and microcracking of cubic ternary zirconium trialuminides

Virk, I. S.; Varin, R.A.

doi:10.1007/bf02801179

Cited by 15 publications

(1 citation statement)

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“…It is well known that addition of fourth-period transition elements including Cu to these intermetallics leads to the stability of the high-symmetry cubic L1 2 phase [2,12,[22][23][24][25][26][27][28][29][30][31][32][33][34][35]. These findings raise the intriguing possibility that such additions to Al-Ti-Zr alloys could give rise to the formation of a stable L1 2 precipitate microstructure.…”

Section: Introductionmentioning

confidence: 99%

Final Report for Department of Energy Grant No. DE-FG02-02ER45997, "Alloy Design of Nanoscale Precipitation Strengthened Alloys: Design of a Heat Treatable Aluminum Alloy Useful to 400C"

Fine¹,

Ghosh²,

Isheim³

et al. 2006

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A creep resistant high temperature Al base alloy made by conventional processing procedures is the subject of this research. The Ni-based superalloys have volume fractions of cubic L1 2 phase precipitates near 50 %. This is not attainable with Al base alloys and the approach pursued in this research was to add L1 2 structured precipitates to the Al-Ni eutectic alloy, 2.7 at. % Ni -97.3 at. % Al. The eutectic reaction gives platelets of Al 3 Ni (DO 11 structure) in an almost pure Al matrix. The Al 3 Ni platelets give reinforcement strengthening while the L1 2 precipitates strengthen the Al alloy matrix. Based on prior research and the extensive research reported here modified cubic L1 2 Al 3 Zr is a candidate. While cubic Al 3 Zr is metastable, the stable phase is tetragonal, only cubic precipitates were observed after 1600 hrs at 425° C and they hardly coarsened at all with time at this temperature. Also addition of Ti retards the cubic to tetragonal transformation; however, a thermodynamically stable precipitate is desired. A very thorough ab initio computational investigation was done on the stability of L1 2 phases of composition, (Al,X) 3 (Zr,Ti) and the possible occurrence of tie lines between a stable L1 2 phase and the Al alloy terminal solid solution. Precipitation of cubic (Al (1-x) Zn x ) 3 Zr in Al was predicted by these computations and subsequently observed by experiment (TEM).To test the combined reinforcement-precipitation concept to obtain a creep resistant Al alloy, Zr and Ti were added to the Al-Ni eutectic alloy. Cubic L1 2 precipitates did form. The first and only Al-NiZr-Ti alloy tested for creep gave a steady state creep rate at 375° C of 8 X 10 -9 under 20MPa stress. The goal is to optimize this alloy and add Zn to achieve a thermodynamically stable precipitate.

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