STTR Phase II: New Process for High Strength/Weight Net-Shape Auto and Aero components from Mg Sheet

这个小型企业技术转移（STTR）二期项目旨在扩大和商业化生产高强度/密度镁（Mg）合金板材的低成本和简单工艺；采用触模热机械加工（TTMP）。TTMP避免了长达数十年的孪晶和剪切带变形障碍，这些障碍限制了商业粗晶镁合金的成形性，相反，在TTMP中，细各向同性晶粒在第一个触模步骤中成型，然后对这些晶粒进行热机械加工，以施加连续的动态再结晶到0.8至2微米的细晶粒。在这种细晶加工方式下，孪生和剪切带最小化，同时促进滑移和晶界滑动。镁合金中常见的金属间相也被细化到纳米尺寸，因此它们可以作为分散硬化剂。细化的微观组织的最终结果是强度和延展性的增加。该机理也适用于钛（Ti）和铍（Be）合金。该项目的更广泛/商业影响是节省汽车和卡车的燃料和污染；航空航天中的燃料和有效载荷效益；电池和燃料电池的节能；生物可替换身体植入物的医疗效益。在商业上，该项目将导致一个新的美国企业制造优质的低成本镁板。

This Small Business Technology Transfer (STTR ) Phase II project aims to scale-up and commercialize a low cost and simple process to produce high strength/density Magnesium (Mg) alloy sheet; using Thixomolding Thermomechanical Processing (TTMP). TTMP avoids the decades-long barriers of twinning and shear band deformation that limits the formability of commercial coarse-grained Mg alloys, rather, in TTMP fine isotropic grains are molded in the first Thixomolding step and then these are thermomechanically processed to impose continuous dynamic recrystalization to finer grains of 0.8 to 2 microns. In this fine grained mode of processing, twinning and shear banding are minimized while slip and grain boundary sliding are promoted. The common intermetallic phases of Mg alloys are also refined to nanometer size so that they can serve as dispersion hardeners. The end result of the refined microstructures is an increase of both strength and ductility. The mechanism may apply also to Titanium (Ti) and Beryllium (Be) alloys.The broader/commercial impacts of this project are fuel and pollutionsavings in automobiles and trucks; fuel and payload benefits in aerospace; energy savings in batteries and fuel cells; and medical benefits in bio-replaceable body implants. Commercially, this project will result in a new U.S. business in manufacture of superior low cost Mg sheet.