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

该小型企业创新研究（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7 xxx合金。与传统的Al-Si铸造合金相比，这些合金由于其高拉伸强度、高温性能和延展性而广泛用于航空航天和汽车工业。然而，在铸造这些合金期间遇到的最大问题之一是在凝固期间形成热裂纹或撕裂。具有长凝固范围、高共晶液相含量和较大铸态枝晶晶粒尺寸的合金比其他合金更容易发生热裂。该项目将联合收割机的控制扩散凝固（CDS）的使用与垂直注入缓慢填充砂铸造工艺。在CDS工艺中，合金的固化通过以受控的质量和热流混合两种不同的液体合金来进行，以实现预定的合金化学，该合金化学以非枝晶微观结构固化而没有热裂。两种合金的混合将在放置在分级砂模下方的垂直压射套筒中进行，随后通过推进柱塞将混合物推入模具中，直到模具充满。预期的结果将是一种能够铸造近净形锻造铝基铸件的方法，其具有上级物理和机械性能，其强度可以是现有Al-Si铸造合金的两倍。使用CDS工艺铸造锻造合金的能力将通过最小化传统铸造缺陷（例如枝晶间收缩和未填充）来改善最终铸造。由于更快的凝固速度和更少的浇注要求，它还将以更低的成本和更快的循环时间生产更高质量的铸件，从而提高产量。锻造铝合金的铸造能力为高温和结构件领域的其他应用开辟了许多机会，这些应用在以前从未有过经济性。这项技术的广泛影响可能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美国生产的所有铸件的33%。军用和商用飞机使用另外30%，其余大部分用于武器和航天器。这项技术创新将提高铝铸件的使用，同时通过提供具有高机械性能的近净形产品来帮助降低部件成本。CDS工艺具有开发具有初生α-Al相和良好互连的枝晶间液相的胞状和/或球状微观结构的全新类别的合金的潜力。这些合金可能具有根本不同的机械和物理性能，这拓宽了潜在的应用。

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.