金属铍热等静压时的动态回复和再结晶行为及其对延性的影响

DRV and DRX Behaviors of Beryllium Powder Sintering Body during HIPingand its Effect on Ductility

摘要:

利用EBSD系统分析热等静压铍晶界分布特征,同时制备无压烧结铍与之对比。发现热等静压铍部分晶粒内部含有十分密集的小晶粒和2°-5°小角晶界,小晶粒尺寸多在几百纳米范围。相反,无压烧结铍晶粒内部不含小晶粒且小角晶界十分稀少,这表明高层错金属铍热等静压时发生了动态回复和再结晶。金属铍热等静压时的动态再结晶行为十分独特,再结晶晶粒在晶内同时大量密集形成,却与基体呈特定取向关系,分别为29°<2 0>/<0001>、59°<2 0>、74°<2 0>、78°<2 11>/<10 0>,及88°<2 0>/<10 0>。这些取向按性质可分为两类,一类为铍的低Σ值重位点阵(CSL)晶界,一类取向轴为铍的滑移方向,其中59°<2 0>和74°<2 0>取向两者皆是。热等静压时铍粉末烧结体高效地回复和再结晶,获得优化的位错结构,是热等静压铍取得高延性的先决条件。提高热等静压温度,能够有效促进铍粉末烧结体的动态回复和再结晶,是提高热等静压延性的有效手段。

Abstract:

Grain boundary character distribution (GBCD) of the hot isostatic pressed (HIPed) beryllium was systematically analyzed by Electron backscatter diffraction (EBSD), and the pressureless sintered beryllium was prepared for making a comparison. It is discovered that some grains of the HIPed beryllium has very dense low angle grain boundaries (LAGBs) of 2°-5° 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 which has very high stacking fault energy not only takes place dynamic recovery (DRV) during HIPing, but also enables access to dynamic recrystallization (DRX). It is very unique that the dynamic recrystallization behavior of the metal beryllium during HIPing. A large number of recrystallized grains are densely formed within grains interior at the same time, but they have a specific orientation relationship with the beryllium matrix. The specific disorientations are 29°<2 0>/<0001>, 59°<2 0>, 74°<2 0> or 78°<2 11>/<10 0>, and 88°<2 0>/<10 0>, respectively. The disorientations can be divided into two categories according to their characteristic. One is that its disorientation axis is the slip direction of beryllium, and the other is the low Σ value coincidence site lattice (CSL) grain boundaries of beryllium, in which 59°<2 0> and 74°<2 0> disorientations are both. The highly efficient recovery and recrystallization of beryllium powder sintered body during HIPing to acquire more optimized dislocation configurations is the prerequisites for the HIPed beryllium to achieve high ductility. Increasing the hot isostatic pressing temperature is able to effectively promote the dynamic recovery and recrystallization of beryllium powder sintered body during HIPing, and thus the ductility of the HIPed beryllium is improved.