Correlation between microstructure and residual stress in the additively manufactured products using advanced experimental characterizations

金属材料（如钢、钛合金和生物相容性金属）的增材制造（AM）概念已经获得了足够的关注，可以制造从简单到复杂形状和几何形状的零件，更有趣的是作为半成品或最终产品。增材制造工艺的巨大好处是，与需要几个步骤的传统制造工艺相反，只需一步就可以打印出产品的完整形状。该工艺经过几十年的发展，已经可以生产100%致密的块状材料。在一些行业，如海洋工业和生物医药工业，正在制造认证产品。然而，由于在增材制造过程中形成复杂的微观结构，在使用中力学性能可能达不到预期。在制造增材制造（AMed）产品的过程中，由于反复的多次热循环引起的清算和凝固循环，会在零件中发现不同程度的恢复、局部塑性变形和结构不连续。与传统产品相比，预制产品具有更高的极限强度，但它们具有较低的延展性**以及高度纹理化的晶粒。这会导致机械评估过程中的过早失效。因此，需要**深入的力学和冶金研究，通过**识别导致早期失效的微观机制和改善力学性能的解决方案来改善零件的微观组织。本项目的主要目标是建立一个经验模型，预测微观组织非均质性、微观组织中积累的残余应变与最终力学性能之间的关系。

The concept of additive manufacturing (AM) in metallic materials such as steels, titanium alloys, and**biocompatible metals has gained enough attention to fabricate parts from easy to complex shape and geometry**more interestingly as semi-final or final products. The huge benefit from AM processes is to print the complete**shape of product in one step in contrary to conventional manufacturing processes where several steps are**required. The process has been developed over a few decades and it has become possible to produce 100%**dense bulk materials. In some industries such as marine industry and biomedical industry, certified products are**being fabricated. However, the mechanical properties may not meet the expectations in service due to complex**microstructure formed during AM processes. Due to repeated multiple thermal cycles induced by the**liquidation and solidification cycles applied to fabricate additive manufactured (AMed) products, different**level of recovery, local plastic deformation and structural discontinuities can be found in parts. As-fabricated**products own higher ultimate strength compared to their conventional versions but they show lower ductility**together with highly textured grains. This causes premature failure during mechanical evaluation. Therefore,**deep mechanical and metallurgical investigations are required to improve the part microstructures by**identifying the micro-mechanisms responsible for early failure and the solutions to improve mechanical**properties. The main objective of this project is described in the above explained context and aims to develop**an empirical model predicting the relationship between microstructural heterogeneities, residual strains**accumulated in the microstructure and resulted mechanical properties.