Characterization of Ni3Al Alloy Fabricated by Thermal Explosion and Hot Extrusion Process

Abstract

In the present paper, the trace B doped Ni₃Al alloy was prepared by the thermal explosion and hot extrusion (TH/HE) technique. Its micro-structure characterization and mechanical properties were carried out by OM, XRD, TEM, compression and micro-hardness tests. Micro-structure examinations exhibit that the TH/HE technology has transformed the powders into Ni₃Al alloy with less porosity. In the synthesized part, coarse and ultrafine Ni₃Al grains comprise the dual-scale grain structure with segregated Al₂O₃ particles along grain boundary. TEM observations reveal that γ-Ni, Al₂O₃ and Ni₃Al phases coexist in the synthesized part. Moreover, the Al₂O₃ particles in the synthesized part have α-Al₂O₃ and γ-Al₂O₃ two crystal structures. In addition, there is a transition region along the interface of Al₂O₃ and Ni₃Al grain. The subsequent hot extrusion optimize the micro-structure of the extruded part by homogenizing the Ni₃Al grain, uniformly distributing Al₂O₃ and generating massive substructures. The great deformation results in the pile-up of dislocations, intersected dislocations and substructures. Moreover, the movement of dislocation promotes the formation of micro-twinning in the Ni₃Al grain, which is accompanied with the stacking faults and nano-structure. The mechanical properties exhibit that the micro-structure optimization caused by the TE/HE technology improves the compressive ductility and strength of the Ni₃Al alloy obviously.

DOI: http://dx.doi.org/10.5755/j01.ms.24.4.19460