Department Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung, Düsseldorf, Germany.
Fraunhofer Institute for Laser Technology ILT, Aachen, Germany.
Nature. 2020 Jun;582(7813):515-519. doi: 10.1038/s41586-020-2409-3. Epub 2020 Jun 24.
Laser additive manufacturing is attractive for the production of complex, three-dimensional parts from metallic powder using a computer-aided design model. The approach enables the digital control of the processing parameters and thus the resulting alloy's microstructure, for example, by using high cooling rates and cyclic re-heating. We recently showed that this cyclic re-heating, the so-called intrinsic heat treatment, can trigger nickel-aluminium precipitation in an iron-nickel-aluminium alloy in situ during laser additive manufacturing. Here we report a Fe19Ni5Ti (weight per cent) steel tailor-designed for laser additive manufacturing. This steel is hardened in situ by nickel-titanium nanoprecipitation, and martensite is also formed in situ, starting at a readily accessible temperature of 200 degrees Celsius. Local control of both the nanoprecipitation and the martensitic transformation during the fabrication leads to complex microstructure hierarchies across multiple length scales, from approximately 100-micrometre-thick layers down to nanoscale precipitates. Inspired by ancient Damascus steels-which have hard and soft layers, originally introduced via the folding and forging techniques of skilled blacksmiths-we produced a material consisting of alternating soft and hard layers. Our material has a tensile strength of 1,300 megapascals and 10 per cent elongation, showing superior mechanical properties to those of ancient Damascus steel. The principles of in situ precipitation strengthening and local microstructure control used here can be applied to a wide range of precipitation-hardened alloys and different additive manufacturing processes.
激光增材制造利用计算机辅助设计模型，通过金属粉末生产复杂的三维零件，具有很大的吸引力。该方法可以数字控制加工参数，从而控制所得合金的微观结构，例如通过使用高冷却速率和循环再加热。我们最近表明，这种循环再加热，即所谓的固有热处理，可以在激光增材制造过程中触发铁镍铝合金中的镍铝沉淀。在这里，我们报告了一种专门为激光增材制造设计的 Fe19Ni5Ti（重量百分比）钢。这种钢通过镍钛纳米沉淀原位硬化，并且马氏体也在 200 摄氏度的易接近温度下原位形成。在制造过程中对纳米沉淀和马氏体相变的局部控制导致了复杂的微观结构层次，从大约 100 微米厚的层到纳米级沉淀物。受古代大马士革钢的启发——古代大马士革钢最初通过熟练铁匠的折叠和锻造技术引入了硬层和软层，我们生产了一种由软层和硬层交替组成的材料。我们的材料具有 1300 兆帕的拉伸强度和 10%的伸长率，表现出优于古代大马士革钢的机械性能。这里使用的原位沉淀强化和局部微观结构控制原理可以应用于广泛的沉淀硬化合金和不同的增材制造工艺。
