双相金属FSW/P过程中的协调变形流动机制及脆性相碎化行为

A coupling model of thermal field, plastic deformation mechanism and material flow will be established to simulate the compatible deformation behaviors and flow field characteristics of dual-phase metals during FSW/P processes. According to that, some similar dual-phase materials will be selected to design the related experiments and simulations, aiming to investigate the deformation mechanism and material flow behaviors at the phase-interfaces between different phases during the FSW/P on the aggregate-type multiphase alloys and dissimilar metals. The properties of aggregate-type multiphase alloys, the proportional changing laws of two different phases, and the quantitative or half-quantitative relationship between the process parameters and the material flow velocities will be investigated and obtainable via the research. The formation mechanisms and the changing laws of interface properties for different phase-boundaries within the FSW/P processed zones will be revealed. Meanwhile, the interaction laws between plastic solid-solution phase and brittle second phase in the distribution-type multiphase alloys will be uncovered. Furthermore, the fragmentation of fragile phases and the quantitative or half-quantitative relationship among the property, quantity, size, shape of fractured fragile phase and the material flow velocities will be also investigated to reveal fracture, fragmentation and diffusion mechanisms of this type alloys during FSW/P. The present research project is believed to provide a strong support for the FSW/P theoretical foundation of multi-phase materials and dissimilar material welds. Meanwhile, it will be significantly meaningful to FSW/P reseach on the more complex multi-phase material systems. Furthermore, the project has great potential application value.

建立双相材料FSW/P过程中的温度场、塑性协调变形及流动的耦合模型，模拟双相金属材料在FSW/P过程中的塑性协调变形机制及流场特征，在此基础上，设计相似材料模拟实验并选用典型的双相金属材料，研究聚合型双相合金及异种金属材料FSW/P过程中异相界面的变形机制及流动规律，获得聚合型双相合金的性质、两相组成的比例变化、工艺参数与流动速度的定量关系或半定量关系，揭示该类合金FSW/P区异相界面的形成机理和界面性质的演变过程；研究弥散分布型合金中塑性固溶体相与脆性第二相的相互作用规律。揭示脆性第二相破断、碎化及破断的第二相性质、数量、大小、形状、工艺参数与流动速度的定量关系或半定量关系，揭示该类合金脆性第二相破断、碎化及弥散的机制。本项目的研究不仅为双相材料的FSW/P及异种材料的FSW奠定重要的理论基础，还对更为复杂的多相材料系统的FSW/P研究具有重要的科学意义，同时具有重大的潜在应用价值。

搅拌摩擦焊接/加工（FSW/P）在异种金属及双相合金领域的应用加速拓展。本项目基于计算流体力学模型和有限体积模型模拟了异种金属FSW焊接过程中的温度场、复相组织协调变形及流场特征；在此基础上，通过异种金属（铝-钢、铝-钛、铝-铜、铝-镍基高温合金）FSW实验，研究了工艺参数(焊接参数、接头型式、偏置量)与异相形状、分布及组成比例、异相界面变形及材料流动的关系，通过SEM，XRD等重点揭示不同区域物相分布、异相界面的形成过程和界面性质的变化规律；研究聚合型双相合金TC4的表层FSP，分析焊接参数对组织硬度的影响及加工区α＋β双相微观组织演变规律，表明改变工艺参数可调控加工区内α/β相比例、β相区及层片α相的晶粒尺寸，加工区的强化机制主要是细晶强化和复相强化；研究弥散型双相合金球墨铸铁QT500的FSP，分析了工艺参数与加工区塑性变形流动、不同区域组织演变及球状石墨的破碎及弥散的关系，表明球状石墨的破碎源于搅拌头的摩擦及塑性变形基体的剪切，加工区致密马氏体相大大提高了基体的硬度；基于单相金属，通过FSP制备金属粉末（钛粉、钨粉）及陶瓷颗粒（WC，Al2O3/TiO2）增强复合改性层，结合XRD，SEM，EDS，EBSD，TEM等显微分析，研究了塑性基体相与增强颗粒的相互作用规律，揭示了工艺参数与脆性颗粒的破碎、破碎颗粒的数量、大小、形状及分布的关系以及增强颗粒对微观组织演变的影响规律，表明颗粒添加产生的载荷传递、晶粒细化、弥散强化作用促进了复合改性层机械强度的提高；探索了异种高分子材料（PC-ABS, ABS-HDPE）的FSW工艺，提出了适用于异种高分子材料的水下FSW技术，揭示了材料流动混合及界面层形态结构的演变规律。本项目的研究为双相材料的FSW/P及异种材料的FSW奠定重要的理论基础，具有巨大的潜在应用价值。