Impression creep behavior of Al–1.9%Ni–1.6%Mn–1%Mg alloy

• Microstructure of Al–1.9%Ni–1.6%Mn–1%Mg was investigated.
• Impression creep properties of the alloy were investigated at 493–513 K under stresses between 420 and 530 MPa.
• Lattice and pipe diffusion climb controlled dislocation creep are the dominant creep mechanism.

In the present study, microstructure and creep behavior of an Al–1.9%Ni–1.6%Mn–1%Mg alloy were studied at temperature ranging from 493 to 513 K and under stresses between 420 and 530 MPa. The creep test was carried out by impression creep technique in which a flat ended cylindrical indenter was impressed on the specimens. The results showed that microstructure of the alloy is composed of primary α(Al) phase covered by a mantle of α(Al)+Ni3Al intermetallic compound. Mn segregated into AlxMnyNiz or Al6Mn phases distributed inside the matrix phase. It was found that the stress exponent, n, decreases from 5.2 to 3.6 with increasing temperature. Creep activation energies between 115 kJ/mol and 151 kJ/mol were estimated for the alloy and it decreases with rising stress. According to the stress exponent and creep activation energies, the lattice and pipe diffusion- climb controlled dislocation creep were the dominant creep mechanism.