Flow behavior and processing map of forging commercial purity titanium powder compact
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Changfu Li and Philip Nash Mechanical, Materials & Aerospace Engineering, Thermal Processing Technology Center, Illinois Institute of Technology, Chicago, Illinois 60616, USA
Damien Mangabhai Research and Development, Cristal Metal Inc., Lockport, Illinois 60441, USA
Weijie Lu State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China (Received 18 December 2014; accepted 13 March 2015)
The flow behavior of forged commercial purity (CP) titanium powder compact was studied by developing a processing map. CP titanium powder was sintered to 94% relative density, then hot compressed in a Gleeble thermal–mechanical simulator at strain rates ranging from 0.001 to 10 s1 and deformation temperatures ranging from 600 to 800 °C. The hot forging process improved the densification to 98–99.9% and reduced the grain size from 93 to 10 lm by the occurrence of dynamic recrystallization. The fully dynamic recrystallization region is in the range of deformation temperature of 750–800 °C and strain rate of 0.001–0.01 s1, with a power dissipation efficiency higher than 40%, determined by constructing a processing map and analyzing the volume fraction of dynamic recrystallization. This research provides a guide for powder compact forging of power metallurgy titanium by providing the hot compression parameters, which can lead to an improved microstructure and densification.
I. INTRODUCTION
Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected], [email protected] DOI: 10.1557/jmr.2015.84
provided. Powder forging combines the traditional PM method with the forging process, which can provide refined microstructure by dynamic recrystallization and densify the porous metal.5 Zhang4 reveals the relationship of relative density with the amount of deformation by simulating Ti–6Al–4V powder compact forging process using three dimension-finite element modeling (3D-FEM). That research shows that the relative density has a relationship with the deformation degree. The microstructure and the flow behavior of titanium alloy are very sensitive to the hot processing parameters.6 By using the approach of developing a processing map, which is widely used to design hot working parameters, the characterization of the forging behavior can be obtained. The processing map developed by Prasad et al.7 consists of a superimposition of a power dissipation map and an instability map, which can indicate the stable and unstable domains during the metal deformation. Research has been done on processing maps for hot working titanium alloys, 8 which also emphasizes the influence of oxygen content during titanium deformation. The instability of the flow behavior of titanium alloy was studied by constructing a processing map and observation of the deformed microstructure.9 Constitutive behavior of titanium and titanium alloys with microstructure evolution was also studied during the hot deformation process.6,10–14 However, there is little
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