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

由合金制成的物体的生产方法有很多，大致可以分为减法制造、粉末冶金和增材制造（3D打印）。前两种做法是成熟的；它们只会逐渐增强。第三个是不同的。同行评议的科普、工程和技术期刊和杂志的内容证明，增材制造已经取得了如此多的成就，3D打印已经从一种奢侈的生产方式转变为一种有用的生产方式。对于高质量的非金属零件，这一结论反映了实际情况，但增材制造的金属合金的力学性能比传统制造的合金要差。原因有很多；其中有一个很重要。将金属粉末的混合物作为新层放置在部分制造的物体的表面上，并用强大的激光束撞击这种结块。这种冲击导致该层瞬间熔化，随后在冷基底表面凝固。这种冻结速度太快，无法用格列佛-沙伊范式来处理；它不会很快形成无定形。在3D打印中，伴随重复步骤的快速凝固是一个独特的过程，导致过冷熔体，从中可能形成亚稳相，因此形成拜占庭微观结构，其晶体学和成分特征可以使用现代表征工具确定。这一信息对于印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合金以及其他具有广泛成分调制的多组分金属系统的微观结构的能力，这可能最终会在增材制造中进行尝试。这种能力不能建立在爱迪生方法的基础上；它必须建立在像样的科学基础之上，而不是建立在毫无艺术感的经验主义之上。2010年，申请人推测，如果热力学上可能的相的组成接近于剩余液体的组成，那么这些相的沉淀将会更容易，因为它们在过冷熔体中的成核不需要缓慢的远程扩散。这个想法可以理解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测试。提出了利用一种可用的熔体旋流器对化学成分和成分不同的金属熔体进行快速凝固，并根据“成分相似”假设判断其可行性。如果它的实用性被证明，那么这个假设将成为一个物理上合理的，计算上简单的预测通过增材制造生产的金属物体的微观结构。

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.