Borba Natascha Z, Afonso Conrado R M, Blaga Lucian, Dos Santos Jorge F, Canto Leonardo B, Amancio-Filho Sergio T
Department of Materials Engineering, Federal University of São Carlos, São Carlos 310, Brazil.
Helmholtz-Zentrum Geesthacht, Center for Materials and Coastal Research, Institute of Materials Research, Materials Mechanics, Solid State Joining Processes, Geesthacht 21502, Germany.
Materials (Basel). 2017 Feb 15;10(2):184. doi: 10.3390/ma10020184.
In the current work, process-related thermo-mechanical changes in the rivet microstructure, joint local and global mechanical properties, and their correlation with the rivet plastic deformation regime were investigated for Ti-6Al-4V (rivet) and glass-fiber-reinforced polyester (GF-P) friction-riveted joints of a single polymeric base plate. Joints displaying similar quasi-static mechanical performance to conventional bolted joints were selected for detailed characterization. The mechanical performance was assessed on lap shear specimens, whereby the friction-riveted joints were connected with AA2198 gussets. Two levels of energy input were used, resulting in process temperatures varying from 460 ± 130 °C to 758 ± 56 °C and fast cooling rates (178 ± 15 °C/s, 59 ± 15 °C/s). A complex final microstructure was identified in the rivet. Whereas equiaxial α-grains with β-phase precipitated in their grain boundaries were identified in the rivet heat-affected zone, refined α' martensite, Widmanstätten structures and β-fleck domains were present in the plastically deformed rivet volume. The transition from equiaxed to acicular structures resulted in an increase of up to 24% in microhardness in comparison to the base material. A study on the rivet material flow through microtexture of the α-Ti phase and β-fleck orientation revealed a strong effect of shear stress and forging which induced simple shear deformation. By combining advanced microstructural analysis techniques with local mechanical testing and temperature measurement, the nature of the complex rivet plastic deformational regime could be determined.
在当前工作中，针对单个聚合物基板的Ti-6Al-4V（铆钉）和玻璃纤维增强聚酯（GF-P）摩擦铆接接头，研究了铆钉微观结构中与工艺相关的热机械变化、接头局部和整体力学性能及其与铆钉塑性变形状态的相关性。选择了与传统螺栓连接具有相似准静态力学性能的接头进行详细表征。在搭接剪切试样上评估力学性能，其中摩擦铆接接头与AA2198角板相连。使用了两个能量输入水平，导致工艺温度在460±130°C至758±56°C之间变化，冷却速度较快（178±15°C/s，59±15°C/s）。在铆钉中发现了复杂的最终微观结构。在铆钉热影响区，识别出等轴α晶粒，其晶界处析出β相，而在塑性变形的铆钉体积中存在细化的α'马氏体、魏氏组织和β斑域。与基体材料相比，从等轴结构到针状结构的转变导致显微硬度提高了24%。通过对α-Ti相的微观织构和β斑取向的铆钉材料流动进行研究，揭示了剪切应力和锻造的强烈影响，这会引起简单剪切变形。通过将先进的微观结构分析技术与局部力学测试和温度测量相结合，可以确定复杂铆钉塑性变形状态的性质。
