Phase equilibria on Ni–Al interface under low oxygen pressure
2009; Elsevier BV; Volume: 480; Issue: 2 Linguagem: Inglês
10.1016/j.jallcom.2009.01.118
ISSN1873-4669
AutoresChin‐Guo Kuo, Wern Dare Jehng, Sheng‐Jen Hsieh, Chien-Chon Chen,
Tópico(s)Advanced materials and composites
ResumoSeventeen phases of the Ni–Al–O system at high temperatures were analyzed using thermodynamic calculations. An Ni–Al–O isothermal stability diagram was obtained from the thermochemical data. The diagram describes the interface equations for Ni/Al intermetallic compounds, Al/Al2O3, and Al2O3/AlXNiY compounds, and their corresponding regions. Four univariant equilibria points and ten bivariant equilibria lines below 1126 K were obtained. The equations for the coexistence points and interface lines were also obtained. A three-domain diagram of Ni–Al–O phase arrangement at temperatures between 900 and 1191 K is shown. Thermodynamic calculations confirmed that the formation of nickel aluminate spinel (NiAl2O4) requires a threshold NiO activity (log aNiO = −205.3/T − 0.347) and the partial pressure of oxygen (logPO2=−24622/T+8atm). In the Ni–Al–O system, aNiO < 0.266 at 900 K, the compounds in the Ni/Al interface are formed in the order Al3Ni(s) → Al3Ni2(s) → AlNi(s) → AlNi3(s) → Al2O3(α). When aNiO < 0.351 at 1911 K, the compounds in the Ni/Al interface are formed in the order AlNi(s) → Al2O3(α).
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