Influences of Initial Microstructures on Portevin‐Le Chatelier Effect and Mechanical Properties of a Ni–Fe–Cr–Base Superalloy

Abstract

Effects of initial microstructures on the Portevin-Le Chatelier effect (PLC) and mechanical properties of a Ni-Fe-Cr-base superalloy are investigated by hot tensile deformation tests. The inverse PLC effect only occurs in the ST (solution treated) and SAT (solution plus δ phases aging precipitation) superalloys when the deformation temperature is above 873 K. Effects of initial microstructures on the temperature range of PLC effect are obvious, that is, the narrowest temperature range for the HS (solution plus γ 0 /γ 00 phases aging precipitation) superalloy, while the widest temperature range for the ST superalloy. The average activation energy for type A/AþB/B serrations can be determined as 65-81 kJ mol À1 , which contributes to the migration of carbon atoms through pipe diffusion. Meanwhile, the average activation energy for type C serration is about 132-175 kJ mol À1 , which is induced by the pipe diffusion of substitutional atoms. An obvious increase in the yield strength with increasing the deformation temperature from 900 to 973 K is observed for the ST and SAT superalloys. Also, the negative strain rate sensitivity is found in the PLC effect regime. The ST and HS superalloys exhibit the ductile fracture. However, a mixture of ductile transgranular and cleavage fracture is observed in the SAT superalloy.

Dynamic Softening Mechanism and an Improved Unified Constitutive Model for an Al–Cu–Mn–Fe–Zr Alloy during Warm Deformation

“…In addition, the strain rate sensitivity sometimes becomes negative, i.e., the flow stress increases at low strain rates, as shown in Figure 3a. This phenomenon is attributed to the dynamic strain aging (DSA), [ 53 ] which may be induced by the interactions of solute atoms and mobile dislocations. [ 54,55 ] In Figure 3c,d, as the temperatures are 200 and 250 °C, the strain rate sensitivity becomes obvious, and the dislocation movement becomes easy.…”

Prediction of Flow Stress and Characterizing the Deformation Mechanism of As‐Extruded 7005 Aluminum Alloy

“…[36] Under low-temperature conditions (temperature < 673 K) and strain rates greater than 0.1 s À1 , in the latter stages of deformation (after a strain of 0.6), the stress increased with increasing strain, which may be attributed to dynamic strain aging (DSA). [37] This phenomenon could result from the interaction between solute atoms and moving dislocations. [38,39] The strain rate sensitivity becomes pronounced at high temperatures (temperature > 723 K), and dislocation motion becomes easier.…”

Archives of Metallurgy and Materials

“…the material becomes more ductile at higher temperatures. a decline in mean flow stress and a change in grain boundary flow behavior combined to produce this effect [20].…”

“…sykes, s.s. Yardley, K.L. Moore, s. Lyon, r. Cottis, acta Materialia 60(20), 7132-49 (2012). doi: https://doi.org/10.1016/j.actamat.2012.09.021 [2] s. nakamura, h. harada, s. raman, p.e.…”