SBIR Phase I: A Casting Process Capable of Casting Wrought Aluminum Based Alloys Using Controlled Diffusion Solidification

这个小企业创新研究（SBIR）第一阶段项目将开发一种铸造工艺，用于铸造锻造铝基合金，如2xxx、3xxx、4xxx、5xxx、6xxx和7xxx合金。与传统的Al-Si铸造合金相比，这些合金具有高抗拉强度，高温性能和延展性，因此广泛用于航空航天和汽车工业。然而，这些合金在铸造过程中遇到的最大问题之一是在凝固过程中形成热裂纹或撕裂。凝固范围长、共晶液体含量高、铸态枝晶晶粒尺寸大的合金比其他合金更容易发生热撕裂。该项目将使用控制扩散凝固（CDS）和垂直注入缓慢填充砂型铸造工艺相结合。在CDS工艺中，合金的凝固是通过混合两种不同的液体合金，控制质量和热流，以达到预定的合金化学性质，以无热撕裂的非枝晶微观结构凝固。两种合金的混合将在放置在分阶段砂型下面的垂直注射套筒中进行，随后通过推进滑枕将混合物推入模具，直到模具充满。预期的结果将是一种能够铸造近网状变形铝基铸件的工艺，具有优越的物理和机械性能，其强度可能是现有铝硅铸造合金的两倍。使用CDS工艺铸造变形合金的能力将通过最小化传统的铸造缺陷（如枝晶间收缩和非填充）来改善最终铸件。由于更快的凝固速度和更少的浇口填充模具，它还将以更快的周期时间以更低的成本生产出更高质量的铸件，提高产量。铸造锻造铝合金的能力为高温和结构件领域的其他应用开辟了许多机会，这些领域在经济上从未接近过。这项技术的广泛影响可能会对零件供应商和铸件的最终用户产生重大的商业影响。优质铝铸件的主要用户是汽车、军事和商业航空航天工业。汽车和金属部件供应商是世界上第二大创收行业，仅次于石油和煤炭产品。汽车和轻型卡车行业使用的铸件占美国总产量的33%。军用和商用飞机使用另外30%，其余的很大一部分用于武器和航天器。这项技术创新将通过提供具有高机械性能的近净形产品，提高铝铸件的使用，同时有助于降低部件成本。CDS工艺有潜力开发出一类全新的合金，具有初生α - al相的胞状和/或球状微观结构和树枝晶间相互连接的液相。这些合金可能具有根本不同的机械和物理性能，这扩大了潜在的应用。

This Small Business Innovation Research (SBIR) Phase I project will develop a casting process to cast wrought Al-based alloys such as the 2xxx, 3xxx, 4xxx, 5xxx, 6xxx, and 7xxx alloys. These alloys are extensively used in the aerospace and automotive industries due to their high tensile strength, elevated temperature properties, and ductility, as compared to traditional Al-Si casting alloys. However, one of the biggest problems encountered during casting of these alloys is the formation of hot cracks or tears during solidification. Alloys with long solidification ranges, higher eutectic liquid contents, and larger as-cast dendritic grain size are more prone to hot tearing than others. This project will combine the use of Controlled Diffusion Solidification (CDS) with a vertically injected slow fill sand casting process. In the CDS process, solidification of the alloy takes place by mixing two different liquid alloys with controlled mass and heat flow in order to achieve a predetermined alloy chemistry that solidifies with a non-dendritic microstructure without hot tears. The mixing of the two alloys will take place in a vertical shot sleeve that is placed below a staged sand mold and the mixture is subsequently pushed into the mold by advancing a ram until the mold is full. The anticipated resultant would be a process capable of casting near net-shaped wrought Al-based castings, with superior physical and mechanical properties, that could be twice as strong as existing Al-Si casting alloys. The ability to cast wrought alloys using the CDS process will improve the final casting by minimizing the traditional casting defects such as interdendritic shrinkage and non-fills. It will also produce a higher quality casting with improved yields at a reduced cost with a faster cycle time, due to a faster solidification rate and less gating required to fill the mold. The ability to cast wrought Al-alloys opens up numerous opportunities for additional applications in the elevated temperature and structural parts areas that have never been approached before economically.The broader impacts from this technology could be significant commercial impact to both parts suppliers as well the end users of the castings. The primary users of premium aluminum castings are the automotive, military, and commercial aerospace industries. Motor vehicles and metallic component suppliers are the second largest revenue-producing industry in the world, surpassed only by petroleum and coal products. The car and light truck industries use 33% of all U.S. produced castings. Military and commercial aircraft use another 30%, with a significant portion of the remainder in weapons and spacecraft. This technological innovation will enhance the use of aluminum castings at the same time help reduce the component costs, by providing a near net shaped product with high mechanical properties. The CDS process has the potential of developing a whole new class of alloys with cellular and/or globular microstructures of primary alpha-Al phase and a well inter-connected inter dendritic liquid phase. These alloys could have fundamentally different mechanical and physical properties, which broadens the potential applications.