T-TRIP: Investigation of transformation induced plasticity during precipitation formation in quenched and tempered steels and maraging steels

T-TRIP项目旨在更深入地研究到目前为止还没有系统研究的相变诱导塑性(TRIP)在钢中机械应力作用下的析出形成过程。为此，从马氏体时效(马氏体时效)钢类和回火钢类中选择了几种钢作为示例材料进行了研究。这些钢种的选择源于重要的技术应用。热处理的钢通常在硬化后回火，导致碳化物的形成。由于制造过程中的残余应力通常存在于钢制构件中，因此在内部载荷的影响下会发生沉淀反应。这尤其适用于通过电磁感应或激光进行的现代表面硬化方法。例如，马氏体时效钢用于焊接工艺或添加剂制造。这些过程导致极高的冷却速度和相关的热致残余应力。由于分层处理，对已经凝固的区域进行重新加热，并在应力和温度升高的影响下启动析出形成。从这两个类别中，将选择沉淀物体积含量不同的钢成分进行本次调查。这些实验包括测量在不同外加拉应力和压应力下跳闸效应的膨胀法，以及等温和连续温度控制。此外，还需研究外加应力对材料力学性能的影响。作为这方面的指标，热处理后的屈服强度和硬度将被测定。下一步，将检查钢类别之间的可转移性，以确定析出类型(回火钢中的碳化物和马氏体时效钢中的金属间化合物)对相变诱发塑性的影响。用X射线和电子显微镜等方法对基体的性能和析出物的形貌进行表征，并结合微观表征结果对力学实验结果进行解释和评价，以便更详细地了解马氏体时效和回火的机制。测量的相变诱发塑性的确定相关性将通过适用于这两类钢的适当模型来描述。特别是，各钢对析出体积含量的依赖关系应与TRIP效应的相变塑性常数特性相关联。最后，根据结果和建立的模型，可以将其转移到热处理和部件变形领域的技术应用中。

The T-TRIP project aims to investigate more closely the so far not systematically studied transformation induced plasticity (TRIP) during the precipitation formation in steels under mechanical stresses. For this purpose, a selection of steels from the class of martensitic aging (maraging) steels and tempering steels are investigated as example materials. The choice of these steel classes results from important technological applications. Heat-treated steels are usually tempered after hardening, resulting in carbide formation. Since residual stresses due to manufacturing are commonly present in steel components, the precipitation reaction occurs under the influence of an internal load. This applies in particular to modern surface hardening methods by means of electro-magnetic induction or lasers. Martensitic aging steels are used, for example, in welding processes or in additive manufacturing. These processes result in extremely high cooling rates and associated thermally induced residual stresses. Due to the layer wise processing, re-heating of already solidified areas occurs and a precipitation formation under the influence of stresses and increased temperatures is initiated. From both classes steel compositions which differ in the volume content of the precipitates will be selected for this investigation. The experiments include dilatometry for the measurement of the TRIP effect at various applied tensile and compressive stresses as well as isothermal and continuous temperature control. In addition, the influence of the applied stress on the resulting mechanical properties of the material is to be investigated. As indicators for this, the yield strength and the hardness after the heat treatment are to be determined. In the next step, the transferability between the steel classes will be examined in order to determine the influence of the precipitation type (carbides in tempered steels as well as intermetallic phases in martensitic aging steels) on the transformation induced plasticity. The properties of the matrix as well as the morphologies of the precipitates will be characterized by means of X-ray and electron microscopic methods.The findings of the mechanical experiments are then to be interpreted and evaluated with the help of the results from the microscopic characterization in order to give a more detailed insight into the mechanisms during martensitic aging and tempering. The determined dependencies of the measured transformation induced plasticity will be described by means of suitable models for both steel classes. In particular, the dependence on the precipitated volume content for the respective steels should be correlated with the transformation plasticity constant characteristic of the TRIP effect. Finally, from the results and created models the transfer to the technological application in the field of heat treatment and component distortion can be made possible.