Effect of long-range ordering in a Ni–Mo alloy on its mechanical properties and corrosion resistance

Excerpt

Ordered alloys and intermetallic compounds are playing an increasingly important role in advanced corrosion applications, e.g. [1]. As design schemes increase in sophistication, the search continues for alloys, which offer higher strength and can handle a larger variety of complex aggressive media in comparison with the conventional alloys. However, the issue of low ductility remains to be an important one and, therefore, efforts are focused on improving ductility and/or innovations in manufacturing technology. Among the most important alloys in this class are the those based upon the Ni–Mo and Ni–Mo–Cr [2, 3, 4]. A common feature of these alloys is that they undergo a series of long-range ordering reactions upon exposure at elevated temperatures [5, 6]. This involves a slight atoms rearrangement on {420}_fcc planes resulting in closely-related superalattices: D1_a (Ni₄Mo), Pt₂Mo-type: {(Ni₂Cr, and Ni₂(Cr,Mo)}, and DO₂₂ (basis for the Ni₃Mo structure) [7]. …