Heat Assisted Dieless Drawing Process of Superplastic Metal Microtubes - From Zn22Al to β Titanium Alloys

2016 ◽  
Vol 838-839 ◽  
pp. 459-467 ◽  
Author(s):  
Tsuyoshi Furushima ◽  
Ken-Ichi Manabe
Keyword(s):  
Cross Sections ◽  
Rate Sensitivity ◽  
Sensitivity Index ◽  
Outer Diameter ◽  
Drawing Process ◽  
Initial Shape ◽  
Dieless Drawing ◽  
Superplastic Alloy ◽  
Strain Rate Sensitivity Index ◽  
Contact Situation

A heat assisted superplastic dieless drawing process that requires no dies or tools is applied to the drawing of a Zn-22Al and β titanium superplastic alloy for not only circular but also noncircular microtubes such as square, rectangular and noncircular multi core tubes having square inner and rectangular outer cross sections. As a result, the tendency has been to increase the limiting reduction in area with increasing strain rate sensitivity index m value. We successfully fabricate Zn-22Al alloy, AZ31 magnesium, β titanium circular microtubes with outer diameter of 191μm, 890μm and 180μm, respectively. Furthermore, a noncircular micro tube, which has inner square tubes with a 335μm side, and an outer rectangular tube of 533×923μm were fabricated successfully. During the dieless drawing process, the geometrical similarity law in cross section which the tube is drawn while maintaining its initial shape can be satisfied. The smooth surface can be obtained in case of superplastic dieless drawing process without contact situation with dies and tools. Consequently, it is found that the superplastic dieless drawing is effective for the fabrication of circular and noncircular multicore microtubes.

Micromechanical Responses of Sn-3.5Ag-xCo Lead-Free Solders by Nanoindentation

2008 ◽  
Vol 580-582 ◽  
pp. 209-212 ◽  
Author(s):  
Feng Gao ◽  
Hiroshi Nishikawa ◽  
Tadashi Takemoto
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Constant Load ◽  
Lead Free ◽  
Sensitivity Index ◽  
Mechanical Evolution ◽  
Strain Rate Sensitivity Index ◽  
Index Value ◽  
Lead Free Solders

The lead-free casting solders Sn-3.5Ag-xCo (x = 0, 0.1, 0.5 and 1.0 mass%, respectively) were subjected to isothermal aging at 150°C for 0, 1008 and 2016 h, respectively. The nanoindentation methodology was employed herein to assess the mechanical properties. In particular, the strain rate sensitivity index value was derived from the creep deformation at the dwell time of the target constant load using Mayo-Nix theory. Basically, there is no remarkable tendency of the variation of Young’s modulus after aging, while to some extent, the hardness of the alloys drops. The strain rate sensitivity index value continues to decrease with the prolonged aging time. The solder grain growth and the coarsening of the intermetallics namely, Ag3Sn and CoSn2, are responsible for the mechanical evolution of the alloys. The 1.0% (mass%) Co additive improved the hardness of the solder alloy, and caused the decrease of the strain rate sensitivity value.

Theoretical Deduction of Constitutive Equations with Variational Parameters during Superplastic Tension

2014 ◽  
Vol 941-944 ◽  
pp. 1509-1512
Author(s):  
Zhi Ping Guan ◽  
Xiao Fang Guan ◽  
Yu Quan Song
Keyword(s):  
Strain Rate ◽  
Test Data ◽  
Constitutive Equations ◽  
Constant Strain Rate ◽  
Rate Sensitivity ◽  
State Equation ◽  
Sensitivity Index ◽  
Tensile Tester ◽  
Strain Rate Sensitivity Index ◽  
Superplastic Tension

In this article, firstly, the strain hardening index and the strain rate sensitivity index were deducted from the general state equation and the mechanical meaning of the two indexes were correspondingly depicted, and then constitutive equations, where both/either of the two indexes appear as constants, were theoretically deducted from the same state equation. Secondly, constitutive equations where both/either of the two indexes present as variables were put forward by numerical simulation. Next, constitutive equations were built, where mechanical variables are replaced by test data obtained on an electronic universal tensile tester with the capacity to carry out a true constant strain rate path. Finally, based on the test data of Zn-5%Al during superplastic tension, it is proved that the theoretical results in this article are valid.

Determination of Superplastic Material Properties for Parent Material and Friction Stir Welded Joint of Al-Alloy AA6061-T6

2015 ◽  
Author(s):  
Senthil Kumar Velukkudi Santhanam ◽  
Ganesh Pasupathy ◽  
Padmanabhan Kuppuswamy Anantha
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Material Properties ◽  
Rate Sensitivity ◽  
Superplastic Forming ◽  
Parent Material ◽  
Sensitivity Index ◽  
Superplastic Material ◽  
Friction Stir ◽  
Strain Rate Sensitivity Index

Superplastic forming (SPF) takes the advantage of the metallurgical phenomenon of superplasticity (SP) to form complex and highly intricate bulk and sheet metal parts. SP refers to the extraordinary formability of certain metals and alloys, ceramics, composites (both metallic- and ceramic-based), dispersion strengthened materials, nanostructured materials and bulk metallic glasses, which allows them to suffer elongations of several hundred percent under the action of tensile forces. The superplastic forming characteristics of materials like aluminium, titanium and magnesium alloys have been clearly identified in order to produce complicated near-net shapes. These materials are used in the aeronautical manufacturing industry and automotive manufacturing industries due to the significant weight (by ∼ 30%) and cost (by ∼ 50%) saving that is possible. Some research work has proved superplastic forming of friction stir welded (FSW) joints also. The FSW joint efficiencies have been characterized by mechanical and metallurgical examination. Studies are also available on the behavior of FSW joints of similar and dissimilar metals. Information on the performance of friction stir welded joints during superplastic forming is rather limited, but it is important to achieve excellent properties in the friction stir welded joints also during superplastic forming. FSP (friction stir processing) – SPF (superplastic forming) is presently being promoted as a very viable near-net shape technology for making very large and complicated sheet metal products. To achieve this superplastic material parameters are much required in industry to develop new shapes. One has to understand the flow rule relationship and mechanics involved during sheet metal forming at high temperature to select the material and forming tool with selected process parameters. This paper deals with the determination of superplastic material properties of non-superplastic aluminum alloy AA6061-T6. The superplastic material properties like strain rate sensitivity index, flow stress and strain rate were determined for both the selected material and friction stir welded sheets at various tool rotation speeds. The superplastic free blow forming experiments were performed for various constant temperatures and pressure for the parent material. Similarly the superplastic free blow forming experiments were performed for the friction stir welded joint for various tool rotation speed at constant temperature. The methods were used to determine the material properties are straight line fit method and polynomial regression method. The superplastic forming height is significantly high in case of the FSW specimens at 2000 rpm, the initial forming rate is faster and the strain rate sensitivity index obtained is also higher when compared to the parent material properties. The strain rate sensitivity index obtained for friction stir welded specimen during superplastic forming was foundto have improved when compared to the parent material.

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