Hot Deformation Behavior and Workability of In Situ TiB2/7050Al Composites Fabricated by Powder Metallurgy

• Main Authors: Haofei Zhu, Jun Liu, Yi Wu, Qing Zhang, Qiwei Shi, Zhe Chen, Lei Wang, Fengguo Zhang, Haowei Wang
• Format: Article
• Language: English
• Published: MDPI AG 2020-11-01
• Series: Materials
• Subjects: aluminum matrix composites; powder metallurgy; thermo-mechanical deformation; microstructure; superplasticity
• Online Access: https://www.mdpi.com/1996-1944/13/23/5319

Isothermal compression tests of in situ TiB₂/7050Al composites fabricated by powder metallurgy were performed at 300–460 °C with the strain rate varying from 0.001 s⁻¹ to 1 s⁻¹. The Arrhenius constitutive equation and hot processing map of composites were established, presenting excellent hot workability with low activation energies and broad processing windows. Dramatic discontinuous/continuous dynamic recrystallization (DDRX/CDRX) and grain boundary sliding (GBS) take place in composites during deformation, depending on the Zener-Hollomon parameter (Z) values. It was found that initially uniform TiB₂ particles and fine grain structures are beneficial to the DDRX, which is the major softening mechanism in composites at high Z values. With the Z value decreasing, dynamic recovery and CDRX around particles are enhanced, preventing the occurrence of DDRX. In addition, fine grain structures in composites are stable at elevated temperature thanks to the pinning of dense nanoparticles, which triggers the occurrence of GBS and ensures good workability at low Z values.