A2 → B2 → L21 ordering transitions in Au–Cu–Al alloys

Gu, Yijia; Jin, Min; Jin, Xuejun

doi:10.1016/j.intermet.2009.02.012

Cited by 20 publications

(22 citation statements)

References 12 publications

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“…At the low temperature stage, a couple of distinct resistivity changes can be seen between 171.6 C and 281.3 C. It implied that structural changes might occur during such heat treatment in the asquenched sample and the details will be discussed later. Then the resistivity increased linearly with temperature until the temperature was up to 495.3 C. Another distinct resistivity change occurred between 495.3 C and 616.5 C, which is in a good agreement with the B2-A2 order-disorder transition [7,12]. Finally, the Au 7 Cu 5 Al 4 alloy returned to A2 disorder structure above 616.5 C, which is accordance with the previous work [7,12].…”

Section: Ordering Transitions In a Quenched Au 7 Cu 5 Al 4 Alloysupporting

confidence: 90%

Ordering transitions in quenched Au7Cu5Al4 alloy and effect of order on martensitic transformation

2010

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Section: Ordering Transitions In a Quenched Au 7 Cu 5 Al 4 Alloysupporting

confidence: 90%

Ordering transitions in quenched Au7Cu5Al4 alloy and effect of order on martensitic transformation

2010

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“…The peak of heat capacity with respect to the temperatures in Fig. 2(b) shows that the ordering-disordering transition between the low-temperature ordered L2 1 phase and the high temperature disordered B2 phase is about 708 K. Our predicted order-disorder transition temperature of Au 2 CuAl is about 20 K higher than the result of experiments (about 687 K [4] ). Such a discrepancy may be ascribed to the fact that the mixing potentials used in energy expansion are obtained from first-principle calculations at T =0 K, in which non-configurational contributions, like lattice vibrations, and electronic excitations are ignored.…”

Section: Monte Carlo Simulationmentioning

confidence: 48%

“…thermal analysis, electrical resistivity and internal friction, are employed to characterize the B2→L2 1 transition [3] . Besides, the experimental results for AuCu-Al systems also have motivated several recent studies employing Bragg-Williams-Gorski (BWG) model to analyze the ordering transition [4] . Whereas the experimental and theoretical studies confirmed the existence of B2→L2 1 ordering transition, the microcosmic mechanisms of the phenomenon is ambiguous.…”

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confidence: 99%

Monte Carlo simulation of B2-L21 ordering transitions in Au-Cu-Al alloy systems

Ding

et al. 2011

J. Shanghai Jiaotong Univ. (Sci.)

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The B2-L21 ordering transitions in Au-Cu-Al shape-memory alloys are studied by the Monte Carlo exchange simulations, where a set of the first, the second and the third nearest-neighbor mixing potentials for CuAl in the Au-Cu-Al alloys are calculated from first principals using the Connolly-Williams methods. To ensure the phase stability of the β-Au-Cu-Al, the investigation includes the range of compositions Au2Cu1−xAl1+x (−0.15 x 0.15). The B2-L21 transition temperatures are predicted, and are in agreement with the experimental results. The atomic ordering around vacancy of the L21 structure is further discussed.The Au-Cu-Al ternary system is a well-known HumeRothery electron compound, which may present a shape memory effect [1] . This alloy also displays attractive glittery surface patterns after martensitic transformation, so, the alloy is named "spangold" [2] . During the cooling, the alloy undergoes A2→B2→L2 1 ordering transitions and subsequent martensitic transformation. Extensive experiments show that the martensitic transformation cannot occur unless the parent phase is in the L2 1 structure and the ordering degree makes a significant effect on the martensitic transformation [3] . The nature of the ordering transition process and the critical transition temperature of B2→L2 1 , however, are still unclear, for the A2→B2 and B2→L2 1 ordering transitions are coupled and cannot be separated from each other easily.Recently, multiple techniques and measurements, e.g. thermal analysis, electrical resistivity and internal friction, are employed to characterize the B2→L2 1 transition [3] . Besides, the experimental results for AuCu-Al systems also have motivated several recent studies employing Bragg-Williams-Gorski (BWG) model to analyze the ordering transition [4] . Whereas the experimental and theoretical studies confirmed the existence of B2→L2 1 ordering transition, the microcosmic mechanisms of the phenomenon is ambiguous. And the static BWG model cannot illustrate the transition processes on cooling treatment. Therefore, in present paper, we apply a generalized lattice model and Monte Carlo simulations in the study of B2→L2 1 ordering transition. The mixing potentials based on Connolly-Williams methods are constucted from the total energies of a series of Au 2 Cu 1−x Al 1+x (−0.15 x 0.15) ordered structures. Subjecting the mixing potentials to Monte Carlo simulations, the order-disorder transition temperature of the Au 2 Cu 1−x Al 1+x is also obtained and compared with experiments.

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“…A further lambda type signal occurs at 911 K where the B2 phase forms. Minor fluctuations of the baseline were detected for some samples in the range from 523 K to 653 where internal friction measurements made on cooling seemed to indicate the occurrence of a phase transformation, claimed to be L2 1 to B2 [5]. No modification of the alloy structure is detected, however (see X-ray patterns in Fig.…”

Section: Thermal Analysis and Phase Constitutionmentioning

confidence: 99%