深冷轧制奥氏体不锈钢组织超细化机理与强韧性控制

The cryorolling is identified as a promising and novel technology to produce ultrafine-grained sheets and greatly improve strength and ductility by deforming them at cryogenic temperature in recent years. For the coarse grain and low strength of austenitic stainless steel in the conventional production conditions, a research idea is proposed with cryorolling and short annealing treatment to obtain ultrafine-grain sheets in this project, by which the strength and ductility of austenitic stainless steel can be greatly improved. The following scientific issues will be researched: 1) Studying the effect of cryorolled metastable austenitic stainless steel on dislocation configuration and the lattice distortion. 2) Observing and controlling the recrystallization behaviors of nucleation and growth about cryorolled sample with short annealing treatment. 3) Discovering the genetic laws of microstructure, texture and grain boundary character evolution in cryorolling and short annealing procedure. 4) Developing the theory about thermodynamic and physical metallurgy on refining grain and studying strength-ductility mechanism in cryorolling conditions. The aims of this project are to establish the theoretical framework of evolution of microstructure and properties of cryorolled austenitic stainless steel with face centered cubic crystal structure, and to obtain the ultrafine-grained austenitic stainless steel samples with submicron grain size (≤0.5μm ) and improved product of strength and elongation (≥40%).The objective of this investigation is to explore a cryorolling theory for developing the material potential properties, which has important significance and practical value for exploring new ways to enhance the material properties.

深冷轧制是近年出现的材料加工新技术，在材料组织超细化、改善强韧性等方面具有显著的作用。本项目针对奥氏体不锈钢在常规生产条件下晶粒组织粗大且强度偏低等问题，提出采用深冷轧制及快速退火过程实现晶粒超细化的研究思路，目的是大幅度提高奥氏体不锈钢强韧性。重点研究以下科学问题：1）深冷轧制对亚稳奥氏体不锈钢位错组态及晶格畸变的影响；2）深冷轧件在快速退火条件下形核、长大等再结晶行为的观测与控制；3）深冷轧制及快速退火过程显微组织、织构及晶界特征演变的遗传规律；4）深冷轧制晶粒细化的热力学与物理冶金学原理及强韧化机理。本研究目标是：建立深冷轧制面心立方结构奥氏体不锈钢组织性能演变与控制的理论框架，获得晶粒尺寸达到亚微米级（≤0.5μm）、强塑积提高40%以上的超细晶奥氏体不锈钢样件。本研究旨在探索深冷轧制技术新体系，用于深入挖掘材料性能潜力，对探索提升材料性能新途径具有重要意义和实用价值。

深冷轧制技术是近年来出现的材料加工新技术，在细化材料组织、改善强韧性等方面表现出显著的效果。针对奥氏体不锈钢在常规生产条件下晶粒粗大且强度偏低等问题，提出采用深冷轧制及快速退火方式实现晶粒超细化的研究思路来提高奥氏体不锈钢的强韧性。本项目经过三年的研究工作，取得了以下的研究成果：. （1）以304奥氏体不锈钢冷轧退火板为实验材料，在实验室条件下，对不锈钢试样进行不同方式的深冷轧制及快速退火处理，研究深冷轧制压下率、退火温度及退火时间、循环退火处理等工艺对不锈钢微观组织的影响。结果表明，晶粒尺寸随退火温度的升高而增大，退火温度对晶粒尺寸的影响程度要大于退火时间。经循环退火处理试样的晶粒尺寸小于一次退火处理，深冷轧制压下率为65%时，其晶粒尺寸仅为一次退火处理的一半，且逆相变比例升高，尺寸分布更加均匀。. （2）对经不同深冷轧制工艺处理的不锈钢试样进行力学性能检测，分别研究了深冷轧制工艺对不锈钢强塑积、维氏硬度、宏观织构及微观织构的影响。结果表明，不锈钢试样的强塑积随退火温度和压下率的增加而上升，经深冷轧制及退火处理试样的强塑积均在20000MPa%以上。不锈钢试样的硬度随退火温度的升高而下降，经深冷轧制及退火处理试样的硬度值均在280HV10以上。退火处理后，不锈钢试样α和γ取向线的取向密度均随退火温度的升高而减弱。. 上述研究成果不仅提供了普通奥氏体不锈钢组织超细化和强韧性控制的新方法，而且还大大丰富了现有物理冶金学知识，为钢铁材料，特别是为逆转变奥氏体钢的显微组织设计和力学性能优化提供了新思路和新方法，因此具有科学意义。