Economical High Strain Rate Superplastic Forming via Friction Stir Processing

超塑性成形用于制造形状复杂的零件和统一的组织。摩擦搅拌工艺已经证明了克服传统超塑性成形的两个主要缺点的强大潜力：(a)超塑性成形速度慢，(b)超塑性起始材料成本高。提出的研究将集中在基本的微观结构-性能-形成的相关性与重叠方案和更大的工具几何。这一研究对于推进基于搅拌摩擦处理的超塑性概念的初步构想和开发突破性的超塑性技术至关重要。增强超塑性的搅拌摩擦加工的基本概念是基于固态摩擦搅拌过程中形成的非常精细的微观结构。这种新的加工工艺将作为实现板料浇铸+搅拌摩擦加工+高应变速率超塑性成形三步近净形制造路线的手段。为了成功开发增强超塑性的搅拌摩擦工艺，需要了解的关键问题包括：(i)搅拌摩擦工艺参数和工具对微观组织发展的影响；（ii）搅拌摩擦过程中重叠孔道对微观结构的影响；（iii）晶粒异常生长的机理及抑制/避免晶粒异常生长的方法；（iv）多道次搅拌摩擦加工材料的显微组织与超塑性性能的相关性。这些问题将在可热处理（7475 Al）和铸造Al- zn - mg - sc合金中进行研究。拟议的研究涉及大学（UMR）和工业（罗克韦尔科学和Superform）的理想结合。拟议研究的更广泛影响包括将创新思想引入本科课程，如金属变形加工和金属结构-性能实验室。在工业方面，Superform是世界领先的超塑性成形部件制造商，如果这一概念能够成功开发，他们的参与将导致技术转让和实施。超塑性成形是一种节能环保的技术，将其应用于更广泛的产品将有助于促进环保制造。

Superplastic forming is used to produce complex shaped components and unitized structures. Friction stir processing has demonstrated a strong potential to overcome two major drawbacks of conventional superplastic forming: (a) slow superplastic forming rates, and (b) high cost of starting material for superplasticity. The proposed research will focus on the fundamental microstructure-property-forming correlations with overlapping scheme and larger tool geometry. Such study is crucial to promote the initial concept and develop breakthrough enabling superplastic technologies based on friction stir processing.The basic concept of friction stir processing for enhanced superplasticity is based on the very fine microstructure that develops during solid-state friction stirring. This new processing technique will be used as a means to achieve a three-step-near-net-shape manufacturing route: casting of sheet + friction stir processing + high strain rate superplastic forming. The critical issues that need to be understood for successful development of friction stir processing for enhanced superplasticity include: (i) influence of friction stir processing parameters and tools on the microstructural development; (ii) the effect on microstructure of overlapping passes during friction stir processing; (iii) the mechanism of abnormal grain growth and ways to suppress/avoid it; and (iv) microstructure-superplastic property correlations in multi-pass friction stir processed materials. These issues will be investigated in heat treatable (7475 Al) and cast Al-Zn-Mg-Sc alloys. The proposed research involves an ideal combination of university (UMR) and industries (Rockwell Scientific and Superform). The broader impact of the proposed study includes bringing innovative ideas to undergraduate courses such as metal deformation processing and metals structure-property laboratories. On the industrial front, Superform is the world's leading manufacturer of superplastically formed components and their involvement will result in technology transfer and implementation if this concept can be successfully developed. Superplastic forming is an energy-efficient and environmentally friendly technology, and expansion of its applicability to a wider range of products will help in promoting environmentally benign manufacturing.