A new approach to predicting precipitation sequences in rapidly solidifying metallic alloys

预测快速凝固金属合金中析出序列的新方法

• 批准号: RGPIN-2018-05503
• 负责人: Malakhov, Dmitri
• 金额: $ 2.04万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=682032
• 关键词: new; approach; predicting; precipitation; sequences

Numerous ways in which objects made of alloys are produced can roughly be divided into subtractive manufacturing, powder metallurgy, and additive manufacturing (3D printing).****The first two praxes are mature; they undergo only gradual enhancements. The third one is different. Contents of peer-reviewed journal and magazines popularising science, engineering and technology attest that so much has been already achieved in additive manufacturing that 3D printing has transformed from an extravagantness to a useful production method. For high quality non-metallic parts, this conclusion reflects the reality, but mechanical properties of additively made metallic alloys are worse than of those made traditionally. Reasons are numerous; one of them stands apart in its importance. A mixture of metallic powders is placed on a surface of a partially fabricated object as a new layer, and this agglomeration is hit by a powerful laser beam. This impact causes an instantaneous melting of the layer followed by its solidification on a cold substrate's surface. This freezing is too fast to be treated within the Gulliver-Scheil paradigm; it is not too quick to result in an amorphous state. Rapid solidification accompanying repetitive steps in 3D printing is a distinctive process leading to supercooled melts, from which metastable phases may form, and therefore to byzantine microstructures whose crystallographic and compositional features can be ascertained using modern characterization tools. This information is vital for an intelligent design of post-printing properties-enhancing heat treatments.****The ultimate goal, however, is not to describe post-printing microstructures, but to acquire an ability to predict them for Al, Ti and Cu alloys as well as for other multicomponent metallic systems with wide compositional modulations, which may eventually be tried in additive manufacturing. Such an ability cannot be based on the Edisonian approach; it must rest on a decent scientific foundation rather than on an artless empiricism.****In 2010, the applicant conjectured that if compositions of thermodynamically possible phases are close to the composition of a remaining liquid, then the precipitation of these phases would be facilitated, because their nucleation within a supercooled melt will not require a slow long-range diffusion. That idea allowed to comprehend outcomes of rapid solidification of Al-Fe-Si melts, but its applicability to various multicomponent systems was never seriously tested.****It is proposed to use an available melt spinner for rapid solidification of chemically and compositionally dissimilar metallic melts, and then to judge on the "compositional similarity" hypothesis feasibility. If its practicality is demonstrated, then the hypothesis will become a physically sound and computationally simple predictor of microstructures of metallic objects produced via additive manufacturing.**

由合金制成的物体的多种生产方式大致可分为减材制造，粉末冶金和增材制造（3D打印）。前两种实践是成熟的，它们只经历逐渐的增强。第三个是不同的。同行评审的期刊和普及科学、工程和技术的杂志的内容证明，增材制造已经取得了如此多的成就，以至于3D打印已经从一种奢侈转变为一种有用的生产方法。对于高质量的非金属零件，这一结论反映了现实，但增材制造的金属合金的机械性能比传统制造的合金差。原因有很多，其中一个因其重要性而与众不同。金属粉末的混合物被放置在部分制造的物体的表面上作为新的层，并且这种聚集被强大的激光束击中。这种冲击导致层的瞬时熔化，随后在冷的基底表面上固化。这种冻结速度太快，无法在格列佛-谢尔范式中处理;它不会太快导致无定形状态。伴随3D打印中重复步骤的快速凝固是导致过冷熔体的独特过程，从中可以形成亚稳相，因此可以使用现代表征工具确定其晶体学和成分特征的拜占庭微观结构。这些信息对于印刷后性能增强热处理的智能设计至关重要。*然而，最终目标不是描述打印后的微观结构，而是获得预测Al，Ti和Cu合金以及具有广泛成分调制的其他多组分金属系统的能力，最终可能会在增材制造中尝试。这种能力不能建立在爱迪生的方法上;它必须建立在一个体面的科学基础上，而不是建立在一个天真的哲学基础上。在2010年，申请人证实，如果化学上可能的相的组成接近于剩余液体的组成，则将促进这些相的沉淀，因为它们在过冷熔体内的成核将不需要缓慢的长程扩散。这一想法使人们能够理解Al-Fe-Si熔体快速凝固的结果，但它对各种多组分体系的适用性从未得到认真的检验。建议使用现有的熔体旋转器快速凝固化学和成分不同的金属熔体，然后判断“成分相似性”假设的可行性。如果其实用性得到证明，那么该假设将成为通过增材制造生产的金属物体微观结构的物理合理和计算简单的预测器。