Effect of Equal Channel Angular Pressing on the Dynamic Softening Behavior of Ti-6Al-4V Alloy in the Hot Deformation Process

Abstract

To investigate the effect of equal channel angular pressing (ECAP) on the deformation of Ti-6Al-4V alloy at a higher temperature, hot compression tests were conducted on alloys having two different initial microstructures (the original alloy (Pre-ECAP) and ECAP-deformed alloy (Post-ECAP)). Post-ECAP, the alloy showed a higher degree of dynamic softening during the hot deformation process due to its finer grain size and higher distortion energy. The flow stress of Post-ECAP alloy was higher than the Pre-ECAP alloy at 500 °C when ε˙= 0.003 s−1. However, the stress of the Post-ECAP alloy decreased rapidly with increasing temperature and strain rate, until the stress value was much lower than that of Pre-ECAP at 700 °C when ε˙= 0.03 s−1. The value of the dynamic softening coefficient revealed that the dynamic softening behavior of Post-ECAP was more pronounced than that of Pre-ECAP in the hot compression deformation process. The main dynamic softening mechanism of Pre-ECAP is dynamic recovery, while the dynamic recrystallization process plays a more important role in the deformation process of Post-ECAP alloy. The microstructures observation results showed that dynamic recrystallization was more likely to occur to Post-ECAP alloys under the same deformation condition. Almost fully dynamic recrystallization had occurred in the deformation process of Post-ECAP at 700 °C and a strain rate of ε˙= 0.01 s−1. The grains of Post-ECAP alloys were further refined. The Post-ECAP alloy exhibits better plastic deformation at temperatures higher than 600 °C due to its significant dynamic recrystallization.

Recent Advances in the Equal Channel Angular Pressing of Metallic Materials

“…Zhao et al preheated the sample to 923 K for 5 min before extrusion and carried out nonisothermal ECAP with the extrusion rate of 20 mm/s and B C route. They found that the average grain size of titanium alloys decreased from 15-20 µm to 5-10 µm and from 30 µm to 10 µm after four passes of ECAP, respectively [32,33]. Jahadi et al reported that the grain size of magnesium alloys was reduced from the initial 20.4 µm to 3.9 µm after four passes of ECAP at 275 • C [34].…”

“…10 μm after four passes of ECAP, respectively [32,33]. Jahadi et al reported that the grain size of magnesium alloys was reduced from the initial 20.4 μm to 3.9 μm after four passes of ECAP at 275 °C [34].…”

“…Figure 3 shows the microstructures of titanium and magnesium alloys after four passes of ECAP. [32]. Reproduced with permission from MDPI.…”

“…Figure 3. TEM image of the material after four passes: (a) titanium alloy[32]. Reproduced with permission from MDPI.…”

Energy Absorbing Properties Analysis of Layers Structure of Titanium Alloy Ti6Al4V during Dynamic Impact Loading Tests

“…However, a high friction coefficient, poor resistance to abrasive wear, and a low hardness limit the possible areas of application of titanium alloys. Therefore, the proper use of these materials requires knowledge of their characteristics and properties [ 2 , 3 , 4 ].…”