Guanjie Li

Effect of Nd on microstructure and mechanical properties of NiAl-based intermetallic alloy

Abstract The influence of Nd on the microstructure and mechanical properties of NiAl–28Cr–5.5Mo–0.5Hf alloy was investigated. The study suggests that appropriate addition of Nd produces an improvement of the compressive strength and ductility of the alloy. In addition, the microstructure of the alloys is also refined gradually with increasing Nd content.

Superplasticity in NiAl intermetallics macroalloyed with iron

In this paper, we aim to examine the superplastic behavior of an extruded Ni-28.5Al-20.4Fe (at.%) alloy, which consists of beta+gamma phases with an average linear intercept grain size of 30-50 mum. Its tensile properties were determined at temperatures from 1123 to 1323 K and initial strain rates from 1.04 x 10(-2) to 1.04 x 10(-4) s(-1). A maximum elongation of 233% was obtained at 1123 K and a strain rate of 5.2 x 10(-4) s(-1). Transmission electron microscope (TEM) observation found many dislocation-free grains adjacent to grains with a high-dislocation density and subgrains and subgrain boundaries, which indicate that dynamic recrystallization has occurred as an efficient accommodation mechanism. Scanning electron microscope (SEM) examination of the fracture sample after superplastic deformation reveals many voids on the fracture surface. By correlating with the results of TEM observation, it is suggested that the superplastic deformation in this alloy should be controlled by a grain boundary sliding-based mechanism accommodated by the movement of dislocation and dynamic recrystallization

Superplasticity and cavity stringers in a multiphase NiAl-based intermetallic alloy

Abstract A multiphase NiAl-based intermetallic alloy has been observed to display superplastic behavior from 1123 to 1223xa0K and strain rates ranging from 3.3×10−2 to 2.2×10−4xa0s−1. A grain boundary sliding-based mechanism is proposed as being responsible for the observed superplasticity. After superplastic deformation, it is observed that cavities are usually aligned parallel to the extrusion direction and the tensile axis. The formation of cavity stringers is suggested to be essentially related not only to cavity nucleation site but also to the nature and characteristics of superplastic deformation.

Superplasticity of a directionally solidified NiAl-Fe(Nb) alloy at high temperature

The superplastic behavior of a directionally solidified (DS) Ni-20Al-27Fe-3Nb intermetallic alloy, which consists of dendritic beta-NiAl phase and interdendritic gamma/-gamma phase, has been investigated. This alloy exhibits superplastic deformation behavior at 950-1100degreesC over an initial strain rate range of 5.2 x 10 (- 4)-1.04 x 10 (2) s (- 1), with the strain rate sensitivity index m = 0.21-0.45. The maximum elongation of 260% with m=0.29 was obtained at 1050 degreesC and an initial strain rate of 5.2 x 10 (- 3) s (- 1). Transmission electron microscopy (TEM) observations indicate that the mechanism of superplastic deformation is the high resistance against strain softening accommodated by the dislocation sliding and dynamic recrystallization