DP1200双相钢基体中共格纳米粒子的控制析出行为研究

Recently, energy-saving and environmental protecting is becoming necessary in the automobile industry. The weight-lighting technique is developed as a key route to reach such end. However, the Lightweight requires the thinning automobile plates can sustain sufficient strength and ductility. If possible, the long life and creep resistance under a harsh environment should be seriously considered.. Here, DP 1200 steel is alloyed with optimized suitable amount and proportional Ti-Mo, the element Y is introduced to react with Ti and O, offering Y-Ti-O contained (YTO) nanocluster and nanoparticles to form the coherent boundaries with DP1200 matrix.. Such coherent structures can improve the steel mechanical properties and creep resistance significantly, and the steel life in harsh condition can be prolonged effectively. A model should be built to understand the formation mechanism of the nano-cluster and nanoparticles reprecipitated from dual phase steel matrix.. Finally, the stable coherent structures between duplex steel matrix and YTO nano-particles precipitated diffusively in the grain can be observed except for the normal precipitates of DP 1200 steel.

节能减排不仅是汽车工业中的关键问题，也是全球气候和能源危机解决的关键一环。车身轻量化是汽车工业节能减排的最有效途径之一。轻量化的瓶颈在于，汽车板要在厚度显著减薄的同时，保持足够的强度和延展性，并且在特定情形下能够在恶劣环境中保有长寿命和抗蠕变性能；然而目前双相钢其强度一般在1000 MPa量级，在恶劣环境下的寿命和抗蠕变性能严重不足。. 本项目选择在常用DP1200钢的基础上，优化Mo-Ti合金比例，通过引入钇（Y）元素，将部分Ti元素转化成Y-Ti-O纳米团簇粒子，在双相钢中弥散分布，并与钢基体形成共格或半共格界面；通过对界面和颗粒内部结构优化，大幅度提高钢的强度、韧性、寿命和抗蠕变性能。实现这一突破的关键在于，掌握控制第二相粒子尺寸的核心因素和最优工艺；深入理解形成第二相粒子与双相钢基体稳定共格界面的基本规律和机理。

众所周知，汽车轻量化的主要方法目前集中在两点目标上：一是降低钢的密度，二是减小钢板尺寸，汽车板要在厚度显著减薄的同时，保持足够的强度和延展性。实现其中任一目标均不容易，两者同时实现将是一种挑战。.本研究采用直径1 nm左右的富勒烯球镶嵌在晶界上，不仅与晶界尺寸匹配，而且该结构在一定温度范围内能够稳定存在。富勒烯球不仅密度远小于铁，而且每个碳原子由3个共价的C-C键连接，不易失效；同时解决了降低钢密度和增强增韧的问题。其次，通过粉末冶金和表面高熵层工艺来实现晶界的尖晶石强化，也可以达到类似的目的。这些通过晶界实现的工艺，将在后续工作中渐次深入，最后实现同时在晶内强化的目标。.进一步地，本研究不仅完成了Y-Ti-O第二相粒子在晶内尺寸的控制，最终形成共格结构的任务，并突破性地发现了无Y元素时，Ti-Al-O等第二相粒子与基体共格的事实。通过预留核心法，在熔炼过程中就已经实现了第二相粒子的尺寸控制，后续热处理过程中将进一步完善第二相粒子更精准调控。