Influence of coarse second phase additions on mechanical properties of NiAl

Abstract

NiAl/Nb and NiAl/Cr composite materials were prepared by a powder metallurgical approach. The content of the second phases varied between 5 and 10 weight percent. The thermodynamic stability of Nb and Cr particles in the NiAl matrix was studied at 1473 K (1200 °C) by means of SEM, XRD and microhardness measurements. In the case of Nb the formation of a Laves phase (NbNiAl) was observed whereas the Cr particles remained stable but were hardened to a remarkable extent due to in-diffusion of Ni and Al. This paper presents the results of three-point bending tests performed on as-HIPed and annealed material at room temperature and elevated temperatures. The yielding behavior at room temperature and the creep behavior at 1200 K (927 °C) were investigated by compression tests.