Influence of pressure on the phase transformation and the precipitation kinetics of high-alloyed steel - experiment and simulation

本项目的目的是研究高等静压对马氏体钢和双相不锈钢相变行为的影响，并为快速冷却过程中的加压热处理提供积极的方面。新开发的热等静压装置集成了快速冷却系统，可在高达200 Mpa的气压下工作，可以在相对较高的压力下研究相变。压力和合金元素含量的增加对马氏体钢硬化的影响将被阐明。除了实验研究外，还将开发用于模拟的材料模型，以定量了解快速冷却过程中压力对真实部件微观结构的影响，并预测热处理后的HIP部件的最终形状。该模型将用于模拟等静压力(例如热等静压)下的热处理过程中的致密化行为。在有限元模型中，将热处理过程中的压力变化和析出行为作为输入变量。这样，可以从热等静压温度预测高压冷却后的残余应力状态。得益于这种模式，该方法将有助于节约能源和大量资源。在数值研究之后，可以得到最佳的温度和压力分布，这可以导致在热等静压工艺和综合热处理后获得完全致密的具有所需组织的部件。

The goal of this project is to study the influence of high isostatic pressure on phase transformation behaviours of martensitic steels and duplex stainless steels and to deduce positive aspects for the heat treatment under pressure during rapid cooling. A newly developed hot isostatic pressing unit with integrated rapid cooling system, which works with a gas pressure up to 200 MPa, allows the research of phase transformation under relative high pressure. The influence of pressure and increased alloying element contents on the hardening of martensitic steels will be clarified. Besides experimental investigations, a material model for simulation will also be developed to quantitatively understand the influence of pressure during rapid cooling on the microstructure of real components and to predict the final shape of the heat-treated HIP component. The model will be applied to simulate the behaviours of densification during heat treatments under isostatic pressure (for example, HIP). The pressure change during the heat treatment and the precipitation behaviour will be considered as input variables in the FEM-model. This way, the prediction of the residual stress state subsequent to cooling under high pressure from HIP temperature is possible. Benefitting from this model, the method will help saving energy and numerous resources. Following the numerical study, optimal temperature and pressure profiles can be obtained, which can lead to fully dense components with a desired microstructure after the HIP process with integrated heat treatment.