Showing papers on "Friction stir processing published in 2001"

Friction Stir Processing: A New Grain Refinement Technique to Achieve High Strain Rate Superplasticity in Commercial Alloys

Abstract: Friction stir processing is a new thermo-mechanical processing technique that leads to a microstructure amenable for high strain rate superplasticity in commercial aluminum alloys. Friction stirring produces a combination of very fine grain size and high grain boundary misorientation angles. Preliminary results on a 7075 Al demonstrate high strain rate superplasticity in the temperature range of 430-510 °C. For example, an elongation of >1000 % was observed at 490 °C and 1 × 10 -2 s -1 . This demonstrates a new possibility to economically obtain a superplastic microstructure in commercial aluminum alloys. Based on these results, a three-step manufacturing process to fabricate complex shaped components can be envisaged: cast sheet or hot-pressed powder metallurgy sheet + friction stir processing + superplastic forging or forming.

Rotary tool for friction stir and processing method using the same

Abstract: PROBLEM TO BE SOLVED: To provide a rotary tool for friction stir which not only secures a desirable processing depth but also performs friction stir in a relatively narrow area and to provide a friction stir processing method using the rotary tool. SOLUTION: This rotary tool for friction stir is provided with a tool body 21 which is nearly pillar-shaped, a tool tip 22 having a conically tapered part 24 which is coaxially disposed on the tip side of the tool body and is tapered, and a groove 25 which is spirally formed on the surface of the conically tapered part of the tool tip and set in such a manner that a peripheral shape in a longitudinal section containing an axial line Lb of the tool body becomes nearly a V-shape. Therein, the groove is set in such a manner that the area of an opposite-inserting side slant face is made to be the area of inserting side slant face or larger, and the rotary tool is used by rotating the tool tip inversely to the screwing direction of the nearly V-shaped groove which is spirally formed.

Metal Forming at Very Low Strain Rates

Abstract: Low strain rate forming processes are carried out at high homologous temperatures (>0.5 T solidus) and strain rates in the range of 10 -5 to 10 -3 s -1 . The materials often have grain size smaller than 10 µm. This chapter describes the phenomenon of superplasticity and the conditions that govern low strain rate superplasticity. It also discusses the different metal forming processes employed in industry and the potential applications of superplastic forming and diffusion bonding. The benefits of friction stir processing for superplastic forming are outlined with an example. The techno-economic aspects are considered in brief.