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

该小型企业技术转移(STTR)第二阶段项目旨在扩大生产高强度/密度镁合金板材的低成本和简单工艺，并将其商业化；使用触变模压热机械加工(TTMP)。TTMP避免了长达数十年的孪生和剪切带变形障碍，这些障碍限制了商业粗晶镁合金的成形能力，相反，在TTMP中，细小的各向同性晶粒在第一个触变模压步骤中被模制，然后进行热机械加工，以实现连续的动态再结晶，形成0.8至2微米的细晶。在这种细晶加工模式下，孪晶和剪切带状组织减少，滑移和晶界滑动得到促进。镁合金中常见的金属间化合物相也被细化到纳米级，因此它们可以用作弥散硬化剂。细化显微组织的最终结果是提高强度和延展性。该机制也适用于钛(Ti)和铍(Be)合金。该项目的更广泛/商业影响是汽车和卡车的燃料和污染节省；航空航天的燃料和有效载荷好处；电池和燃料电池的能源节省；以及可生物替代人体植入物的医疗好处。在商业上，该项目将在美国产生一项生产优质低成本镁板材的新业务。

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.