【摘要】 采用扭转变形和退火处理调控MP35N合金的微观结构并改善其力学性能，对其力学行为进行微观机理分析。研究结果表明：扭转变形在合金径向上引入了梯度位错密度，使应变最大的表面处晶粒细化并引入大量层错。梯度结构的引入使得扭转变形后合金的强度显著提高至约767 MPa，同时拥有可观的均匀伸长率(约40%)；进一步的退火处理并未改变扭转变形引入的梯度结构(包括梯度位错密度和晶粒尺寸)，但退火处理导致合金中一部分位错的湮灭，并使得表面区域的层错转变为纳米孪晶。退火处理导致纳米孪晶的形成以及“铃木(Suzuki)效应”的作用使得合金发生了二次硬化。退火过程产生的二次硬化与位错湮灭导致的退火软化相抵消，二次硬化提供的强度约为76 MPa。更多还原

【Abstract】 The torsional deformation and annealing treatment were carried out to regulate the microstructure and mechanical properties of MP35N alloy. In addition, the microscale mechanisms related to the mechanical behaviors were investigated. The results show that the gradient dislocation density is introduced along the radial direction during the torsional deformation. Apart from that, it can be seen clearly that not only the grains are refined but also a great number of stacking faults are induced at the surface region where the strain is maximum.The introduction of gradient structure significantly enhances the strength of sample after torsional deformation up to approximately 767 MPa, and remains considerate uniform elongation about 40% simultaneously. Subsequent annealing treatment makes no difference to the gradient structure including gradient dislocation density and grain size that were introduced during the torsional deformation. However, annealing treatment gives rise to the annihilation of a portion of dislocations in the alloy and leads to a microstructural transformation from stacking faults to nanotwins at the surface region. Considering the formation of nanotwins resulted from annealing treatment and the impact of Suzuki effect, there is a secondary-stage hardening that can partly offset the softening due to dislocation annihilation. It has been estimated that the strength provided by the secondary-stage hardening is around 76 MPa.更多还原