Temperature-Dependent Compressive Deformation Behavior of Commercially Pure Iron Processed by ECAP

doi:10.1007/s40195-015-0229-5

摘要/Abstract

Abstract:

To explore the temperature dependence of deformation behavior of BCC structural materials and the relevant effect of pre-annealing, commercially pure iron (CP Fe) produced by equal-channel angular pressing (ECAP) is selected as the experimental material. The influences of deformation temperature T and pre-annealing on deformation behavior, surface deformation characteristics and substructures of ECAP Fe were systematically studied. The results show that ECAP Fe undergoes a remarkable strain softening stage after a rapid strain hardening during uniaxial compression, and the softening degree and the yield strength σ_YS first decrease and then increase with raising temperature. Pre-annealing at 400 °C effectively weakens the strain softening degree and increases σ_YS. To understand the influence of deformation temperature on deformation behavior, as well as the relevant pre-annealing effect, deformation and damage characteristics and dislocation structures are studied in detail. In a word, the strain softening of ECAP Fe is associated not only with internal structural instability, but also with temperature, and pre-annealing at 400 °C improves high-temperature mechanical properties of ECAP Fe.

Key words: ECAP Fe, Uniaxial compression, High-temperature mechanical behavior, Pre-annealing, Deformation features, Microstructure

. [J]. 金属学报英文版, 2015, 28(5): 531-541.

Ying Yan, Yue Qi, Qing-Wei Jiang, Xiao-Wu Li. Temperature-Dependent Compressive Deformation Behavior of Commercially Pure Iron Processed by ECAP[J]. Acta Metallurgica Sinica (English Letters), 2015, 28(5): 531-541.

图/表 14

Fig. 1 Variation of Vickers hardness with annealing temperature for ECAP Fe

Fig. 2 Metallographs showing the microstructures along the rod axes of CP Fe a and ECAP Fe unannealed b and pre-annealed at 300 °C c and 400 °C d for 1 h; arrows in Fig. 2c show the fine recrystallized regions

Fig. 3 True stress-strain curves of CP Fe and ECAP Fe compressed at different temperatures and a strain rate of 10-2 s-1

Fig. 4 Comparisons of true stress-strain curves of ECAP Fe unannealed and pre-annealed at 400 °C at different compressive temperatures and a strain rate of 10-2 s-1: a RT; b 100 °C; c 200 °C; d 300 °C

Fig. 5 Variation of σYS with deformation temperature for CP Fe and ECAP Fe unannealed and pre-annealed at 400 °C

Fig. 6 SEM images of the surface deformation features for CP Fe compressed at different temperatures and a strain rate of 10-2 s-1: a, b RT; c 100 °C; d 200 °C; e, f 300 °C

Fig. 7 Low-magnification SEM images of the surface deformation features for ECAP Fe compressed at different temperatures and a strain rate of 10-2 s-1: a RT; b 100 °C; c 200 °C; d 300 °C

Fig. 8 High-magnification SEM images of the surface deformation features for ECAP Fe compressed at different temperatures and a strain rate of 10-2 s-1: a RT; b, c 100 °C; d, e 200 °C; f 300 °C

Fig. 9 SEM images of the surface deformation features for ECAP Fe annealed at 400 °C at different temperatures and a strain rate of 10-2 s-1: a RT; b, c 100 °C; d 200 °C; e, f 300 °C

Fig. 10 TEM images of the microstructures of CP Fe compressed to a 45% strain amount at different temperatures and a strain rate of 10-2 s-1: a, b RT; c, d 100 °C; e 200 °C; f 300 °C

Fig. 11 TEM images of the microstructures of ECAP Fe: a, b, c unannealed; d, e, f pre-annealed at 400 °C

Fig. 12 TEM images of the microstructures of ECAP Fe compressed to a 45% strain amount at different temperatures and a strain rate of 10-2 s-1: a, b RT; c 100 °C; d, e 200 °C; f 300 °C

Fig. 13 TEM images of the microstructures of ECAP Fe annealed at 400 °C compressed to a 45% strain amount at different temperatures and a strain rate of 10-2 s-1: a, b RT; c 100 °C; d 200 °C; e, f 300 °C

Fig. 14 Schematics of the major differences in deformation features and substructures after compressive deformation among CP Fe (a), the ECAP Fe unannealed (b) and annealed at 400 °C (c)

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