爆炸复合界面内非（纳米）晶及ASB内组织形成机制

【作者】 熊俊；

【导师】 杨扬；

【作者基本信息】 中南大学 ， 材料加工工程， 2004， 硕士

【摘要】 借助透射电子显微镜(TEM)和高分辨电子显微镜(HREM)实验技术和MATLAB计算软件，研究了爆炸复合界面层内的纳米晶与非晶及其形成原因，并定量的分析和探讨了绝热剪切带内纳米晶组织的形成演化机制。 TEM和HREM观察表明，TA2／TA2爆炸复合界面层内共存着大量的纳米晶和非晶。这些纳米晶晶格完整、其内没有缺陷，晶粒尺寸分布在2nm到50nm，其晶界是共格界面，从而可以保证晶界的高强度。界面层内的非晶则呈现出长程无序特征，并与纳米晶共存。利用爆炸复合界面的温度场模型对界面熔层冷却速率的定量分析表明：在TA2／TA2爆炸复合完成的瞬间，冷却速率高达10~8K／s，在非晶态转变温度(T_g)时的冷却速率高达10~6K／s。爆炸复合界面熔层的高冷却速率、爆炸复合过程中界面承受的高压力、高剪切应力都是形成非晶的有利条件。 TEM观察表明绝热剪切带(ASB)中心区域由30-70纳米的等轴晶组成。一种基于力学辅助的旋转式动态再结晶(RDR)机制可以很好的解释ASB内组织的演化过程。将热／力学、再结晶动力学与微观组织演化过程有机结合起来，定量的分析了ASB内纳米晶组织在变形和冷却过程中的演化。 根据能量守恒原理，建立了一个用于计算绝热剪切带内的组织在演化过程中的亚晶尺寸的公式：对于TA2中的绝热剪切带，计算得L=29.4nm，与TEM观察到的绝热剪切带内的晶粒尺寸30-70nm十分符合。更多还原

【Abstract】 The amorphous and nano-sized grains within the explosive cladding interface were observed by means of transmission electronic microscope (TEM) and high-resolution transmission electron microscope (HRTEM). Their forming reasons were studied using a scientific-calculational software (MATLAB). The microstructure evolution of the nano-sized grains within the adiabatic shear bands was also analyzed quantitatively.The observation by mean of TEM and HRTEM indicated that the amorphous and nano-sized grains co-existed within the TA2/TA2 explosive cladding interface. The size of the nano-sized grains was 2-50 nm. Typical nano-sized grain had a conjunct interface with the matrix, ensuring the high strengthening of the interface. A model for the temperature field was used to quantitatively analyzing the cooling rate. The cooling rate was about 108K/s after the explosive cladding, and it was still about 106K/s when the temperature was cooled to the amorphous phase transition temperature (Tg). The high cooling rate, high pressure and high shearing stress were all advantageous factors to form amorphous phase.TEM observation showed that the center of the adiabatic shear band (ASB) was composed of recrystallized nano-grains (about 30-70 nm in diameter). A Rotational Dynamic Recrystallization (RDR) mechanism which based on mechanics assistance can well explain the microstructure evolution within the ASB. The microstructure evolution of nano-sized grains within ASB during the deformation and cooling stage was analyzed quantitatively by combining thermal-mechanics and recrystallization kinetics with microstructure evolution.By the law of conservation of energy, an equation was proposed to calculate the subgrain size during the microstructure evolution of ASB:for the ASB within TA2, the calculation showed L=29.4 nm. It is very consistent with the TEM observations (i.e. the grain size was 30-70 nm in diameter).更多还原