DRV and DRX Behavior of Beryllium Metal During HIP and Its Effect on Ductility

Grain boundary character distribution (GBCD) of the hot isostatic pressed ( HIPed) beryllium was systematically analyzed by electron backscattered diffraction ( EBSD), and the pressureless sintered beryllium was prepared for comparison. It is found that some grains of the HIPed beryllium have very dense low angle grain boundaries (LAGBs) of 2 degrees-5 degrees and a large number of fine-grains within grain interiors. The size of fine-grains is mostly in the range of hundreds of nanometers. Conversely, the pressureless sintered beryllium has few LAGBs and no fine-grains. The results show that the beryllium has very high stacking fault energy, which results in not only the dynamic recovery (DRV) during HIP, but also dynamic recrystallization (DRX). The dynamic recrystallization behavior of the metal beryllium during HIP is very unique. A large number of recrystallized grains are densely formed within grains at the same time, but they have a specific orientation relationship with the beryllium matrix. The specific disorientations are 29 degrees<2<(1)over bar>(1) over bar0>/<0001>, 59 degrees<2<(1)over bar>(1) over bar0>, 74 degrees<2<(1)over bar>(1) over bar0>, or 78 degrees<2 <(3)over bar>11>/<10<(1)over bar>0>, and 88 degrees<2<(1)over bar>(1) over bar0>/< 10<(1)over bar>0>. The disorientations can be divided into two categories according to their characteristics. One is that the disorientation axis is the slip direction of beryllium, and the other is the low Sigma value coincidence site lattice (CSL) grain boundaries of beryllium. Additionally, 59 degrees<2<(1)over bar>(1) over bar0> and 74 degrees<2<(1)over bar>(1) over bar0> disorientations belong to both categories. The highly efficient recovery and recrystallization of beryllium powder sintered body during HIP can acquire more optimized dislocation configurations, which is the prerequisites for the HIPed beryllium to achieve high ductility. Increasing the hot isostatic pressing temperature is able to effectively promote the DRV and DRX of beryllium powder sintered body during HIP, and thus the ductility of the HIPed beryllium is improved.