High strain rate superplasticity of TiN P /2014Al composite

Abstract

Superplasticity of the TiN_p/2014AI composite prepared by powder metallurgy method was investigated by tensile tests conducted at different temperatures (773, 798, 818 and 838 K) with different strain rates range from 1·7×10° to 1·7×10⁻³s⁻¹. Results show that a maximum elongation of 351 is achieved at 818 K and 3·3·10⁻¹s⁻¹. At different deformation temperatures, the curves of m value can be divided into two stages with the variation of strain rate and the critical strain rate is 10⁻¹ s⁻¹. Superplastic deformation activation energy in the TiN_p/2014AI composite is 417 kJ mol⁻¹, which is related to liquid phase formation at triple points of grain boundaries and interfaces between the matrix and the reinforcement. Superplastic deformation mechanism of the TiN_p/2014AI composite is grain boundary sliding accommodate mechanism when the strain rate is lower than 10⁻¹ s⁻¹, and transfers to grain boundary sliding accommodation mechanism plus liquid phase helper accommodation mechanism when the strain rate is higher than 10⁻¹ s⁻¹