Superplastic Zn-Al Alloy Research Articles

Critical issues in conducting constant strain rate nanoindentation tests at higher strain rates

Constant strain rate nanoindentation is a popular technique for probing the local mechanical properties of materials but is usually restricted to strain rates ≤0.1 s−1. Faster indentation potentially results in an overestimation of the hardness because of the plasticity error associated with the continuous stiffness measurement (CSM) method. This can have significant consequences in some applications, such as the measurement of strain rate sensitivity. The experimental strain rate range can be extended by increasing the harmonic frequency of the CSM oscillation. However, with commercial instruments, this is achievable only by identifying higher CSM frequencies at which the testing system is dynamically well behaved. Using these principles, a commercial system operated at the unusually high harmonic frequency of 1570 Hz was successfully used to characterize of the strain rate sensitivity of a Zn22Al superplastic alloy at strain rates up to 1 s−1, i.e., an order of magnitude higher than with standard methods.

Micro Deep Drawability of the Superplastic Zn–22Al Alloy at a High Strain Rate and Room Temperature

Abstract This study aimed to investigate the micro deep drawability of the Zn–22Al alloy at room temperature in which it shows superplastic properties. To this goal, first the two-step equal channel angular extrusion (ECAE) process was carried out to obtain an ultra-fine-grained structure (UFG). Upon achieving the grain size of 200 nm, the formability of the alloy at room temperature and at a high strain rate was investigated both experimentally and numerically. Micro deep drawing experiments were performed at different deep drawing ratios (1.66, 1.84, 2.0, and 2.25) and for different sheet thicknesses (0.2, 0.4, and 0.6 mm). The finite element model of the micro deep drawing was also established to assess and compare the thickness variation in deep drawn parts. Results showed that the superplastic Zn–22Al alloy has a great potential in microforming applications. It was also noted that the limiting drawing ratio can be obtained as high as 2.25 in the room temperature condition.

Experimental and Numerical Investigation of Thickness Distribution in Forming of Superplastic Zn-22Al Alloy

Bu çalışmada, süperplastik Zn-22Al alaşımının oda sıcaklığındaki şekillendirilebilirliği deneysel ve sayısal olarak incelenmiştir. İlk olarak, Zn-22Al alaşımı döküm yoluyla üretilmiş ve eş kanallı açısal ekstrüzyon (EKAE) yöntemi uygulanarak tane boyutu 200 nm düşürülmüştür. Erichsen testleri 1x10-1 , 1x10-2 ve 1x10-3 s-1 deformasyon hızlarında gerçekleştirilmiştir. Deneysel çalışma sonrası, Ls-Dyna sonlu elemanlar yazılımı kullanılarak Erichsen testinin sonlu elemanlar analizleri yapılmış, deneysel ve sayısal olarak elde edilen kalınlık değişimleri karşılaştırılmıştır. Zn-22Al alaşımının oda sıcaklığında süperplastik şekillendirilebildiği gösterilmiş, ve bu malzeme için elde edilen deneysel ve sayısal sonuçlar arasındaki uyum göz önüne alındığında süperplastik şekillendirmenin sonlu elemanlar yöntemi ile yeterince hassas olarak modellenebildiği gösterilmiştir.

Trials of Mechanically Interlocking Zn-22Al Superplastic alloy with Optical Fiber by Using Friction Stir Forming

Trials of Mechanically Interlocking Zn-22Al Superplastic alloy with Optical Fiber by Using Friction Stir Forming

Grain Refinement of Zn–22Al Superplastic Alloy Using Friction Stir Processing

Grain Refinement of Zn–22Al Superplastic Alloy Using Friction Stir Processing

Friction stir forming for mechanical interlocking of insulated copper wire and Zn-22Al superplastic alloy

In this study, a novel method of friction stir forming (FSF) was conducted for mechanical interlocking of Zn-22Al superplastic alloy and thin copper wire insulated by polyimide. The potential development of a composite material capable of transmitting electrical energy or electric signals was studied experimentally, and it was concluded that FSF can successfully interlock insulated copper wire with Zn-22Al superplastic alloy. The authors suggest the possibility that FSF could join sheets of Zn-22Al alloy by pressure welding and superplastic forming and diffusion bonding (SPF/DB). Trials of FSF were carried out on a modified vertical milling machine. The results are discussed in terms of microstructure observations, hardness distributions, and temperature measurements.

Effects of grain size on room temperature deformation behavior of Zn–22Al alloy under uniaxial and biaxial loading conditions

Effects of grain size on room temperature (RT) deformation behavior of superplastic Zn–22Al alloy under uniaxial and biaxial loading conditions were investigated. Two–step equal channel angular pressing (ECAP) and subsequent annealing processes were applied to the alloy in order to obtain microstructures with various grain sizes ranging from submicron to micron sizes. Grain size of 200nm was achieved after ECAP of the alloy, and it was increased up to ~2.60µm by annealing at 250°C for different time periods. Changes in deformation behaviors of the alloy with various grain sizes were found to be in good agreement under the uniaxial tensile and biaxial Erichsen test conditions. Increasing grain size decreased both the maximum elongation under uniaxial deformation and limiting dome height (LDH) under biaxial deformation. The high elongation to failure and LDH values for the samples with submicron grain size were attributed to their high strain rate sensitivity.

Production of a Superplastic Vibration-Damping Steel Sheet Composite Using Friction Stir Forming

This study proposes a novel method of manufacturing composite vibration-damping steel sheet with Zn-22Al superplastic alloy using friction stir forming (FSF). Trials of mechanical interlocking of steel sheet with Zn-22Al superplastic alloy using FSF were carried out on a modified milling machine. The results are discussed in terms of residual microstructures and mechanical properties. We concluded that cladding steel sheet with Zn-22Al superplastic alloy using FSF results in superplastic forming and diffusion bonding.

Energy Absorption of Superplastic Zn-22Al Alloy Foam Manufactured through Melt Foaming Process

Closed-cell superplastic Zn-22Al alloy foams were manufactured through the melt foaming process using sodium hydrogen carbonate powder as a foaming agent. Foaming tests were carried out under different foaming temperatures, times and additive amounts of foaming agent. The porosity of Zn-22Al alloy foams were between 30 and 70%. The cell wall consisted of fine equiaxial crystal grains after solution treatment. The compressive properties of the Zn-22Al alloy foams were investigated at room temperature and high temperature. Zn-22Al alloy foams exhibited high strain rate sensitivity, which was caused by superplastic deformation of the cell wall material.

Strain Rate Sensitivity and High Temperature Deformation Mechanisms of Cast Zn-22Al Alloy Foams

Zn-22Al eutectic alloy is a typical superplastic material which exhibits over 500% elongation at high temperature. Superplastic Zn-22Al alloy foams were successfully manufactured through a conventional casting process. Foaming temperature was about 750K which was lower than that of conventional aluminum foams. The porosity of Zn-22Al alloy foams is between 50 and 80%. The cell wall consisted of fine equiaxial crystal grains after solution treatment. High temperature deformation behavior of Zn- 22Al alloy foams was evaluated through tensile and compressive tests at high temperature. Zn-22Al alloy foams exhibited high strain rate sensitivity of 0.55, which was caused by superplastic deformation of the cell wall material. High temperature deformation mechanism can be explained using the new parameter of local strain rate. The Zn-22Al foams showed relatively high ductility at high temperature compered to aluminum foams. This is because of the superplastic deformation induced by the fine microstructure in the cell wall. In addition, most superplastic materials have excellent damping property due to their grain boundary sliding. Present Zn-22Al foams are applicable as either shock absorbing or damping material in the future.

Fabrication of noncircular multicore microtubes by superplastic dieless drawing process

A superplastic dieless drawing process that requires no dies or tools is applied to the drawing of a Zn–22Al superplastic alloy for noncircular microtubes such as square, rectangular and noncircular multi core tubes having square inner and rectangular outer cross-sections. In this study, the effects of heating condition, such as heating length and the use or nonuse of cooling device, on deformation behavior are investigated. As a result, a square microtube with 0.58mm side and a rectangular microtube of 0.75mm×1.3mm were fabricated after 3-pass superplastic dieless drawing. In addition, the fundamental deformation behavior of noncircular tubes combined with square and rectangular tubes during the dieless drawing process has been clarified experimentally. The cross-sectional shape of the noncircular tubes after the superplastic dieless drawing process tends to be maintained on the basis of the similarity law in case of a wide heating length compared with a narrow heating length. Furthermore, a noncircular microtube, which has inner square tubes with a 335μm side, and an outer rectangular tube of 533μm×923μm were fabricated successfully after a 4-pass superplastic dieless drawing process. Consequently, it was found that the superplastic dieless drawing is effective for the fabrication of noncircular multicore microtubes.

Effect of Porosity on Tensile and Compressive Deformations of Superplastic Zn-22Al Alloy Foam

Closed-cell Zn-22Al superplastic alloy foams were manufactured through the melt foaming process. The Zn-22Al foams were produced with varying porosity of 51-71%. The tensile and compressive properties of the Zn-22Al foams were investigated at 523 K. The compressive specimen has m-value of 0.55 in the low strain rate region. This is because of the superplastic deformation induced by the fine microstructure of the cell wall. Though the superplastic elongation was not obtained in high temperature tensile test, the elongation was higher than that of conventional aluminum foams.

Corrosion behaviour of superplastic Zn–Al alloys in simulated acid rain

The influence of aluminium content on the corrosion behaviour of superplastic Zinc–Aluminium alloys immersed in simulated acid rain was investigated. ZA4, ZA8, ZA12, and ZA16 alloys were used for the test. The Al-rich phase was prone to preferential attack when the superplastic Zn–Al alloy was immersed for 5d. However, with increasing ratios of the Al phase, the corrosion rates of the four samples decreased in the order ZA4>ZA8>ZA12>ZA16. The corrosion rate of the alloy decreased with increasing Al content, which may be related to the distribution of the Al-rich phase. Corrosion kinetic parameters were also calculated.

G040036 Zn-22A1超塑性合金の摩擦撹拌重ね接合

Friction stir welding (FSW) is a relatively new solid state joining process primarily for aluminum alloys. FSW process can also be applied to the welding of a variety of other materials, including magnesium alloys, titanium alloys, stainless steels and metal matrix composites. However, very little information is available regarding FSW characteristics of superplastic alloys. In this study, trials with friction stir lap welding of superplastic Zn-22Al alloy were carried out on a modified milling machine. The results of FSW performed on superplastic Zn-22Al alloy were discussed in terms of the possibility of the development of bulk superplastic Zn-22Al alloy.

The Mechanical Properties of the Superplastic Zn-22Al Alloy at Different Processings

To develop a superplastic damper, the mechanical properties of the superplastic Zn-22Al alloy differently processed are studied by the test, at room temperature. It is indicated that the alloy at the air cooling after rolling processing has better mechanical properties at room temperature, such as higher ductility and lower work-hardening, which is very useful to a seismic damper.

Research on Superplastic Zn-22Al Alloy with a Large Size to a New Seismic Damper

To develop a superplastic damping device, the mechanical properties and superplastic capability of Zn-22Al alloy with a large size in the rolled samples were investigated. It is indicated that the alloy with a large size has some advantage properties, such as high ductility, low yield stress and low work hardening at room temperature, which is very useful to a seismic damper.

Energy Absorption Capability of Zn-22Al Superplastic Alloy Foam Manufactured through Melt Foaming Process

Energy Absorption Capability of Zn-22Al Superplastic Alloy Foam Manufactured through Melt Foaming Process

Superplasticity for Lightweight Metal Foams

Potential applications of superplasticity for lightweight metal foams are reviewed in this paper. Metal foams have been used for lightweight structures, biomedical implants, filters, heat exchangers, sound absorbers and mechanical damping devices. Superplasticity has advantages on metal foaming process and mechanical properties of metal foams. Four examples of metal foams combined with superplastic forming are presented; (i) Enhanced foaming under internal stress superplastic condition, (ii) Superplastic diffusion-bonding of metal foams, (iii) Superplastic forming and foaming and (iv) Superplastic Zn-22Al alloy foam for energy absorbing material.

Energy Absorption Capability of Zn-22Al Superplastic Alloy Foam Manufactured through Melt Foaming Process

Superplastic Zn-22Al alloy foams were manufactured through the melt foaming process using titanium hydride powder as a foaming agent. The compressive properties of the Zn-22Al foams were investigated under quasi-static and dynamic loading conditions. Experimental results show that the flow stress and the energy absorption of the Zn-22Al foam significantly increased with increasing the strain rate. At high strain rate region, the energy absorption of the Zn-22Al foams is also larger than that of conventional aluminum foams. These behaviors are due to superplastic deformation of cell walls.

Superplasticity for Lightweight Metal Foams

Potential applications of superplasticity for lightweight metal foams are reviewed in this paper. Metal foams have been used for lightweight structures, biomedical implants, filters, heat exchangers, sound absorbers and mechanical damping devices. Superplasticity has advantages on metal foaming process and mechanical properties of metal foams. Four examples of metal foams combined with superplastic forming are presented; (i) Enhanced foaming under internal stress superplastic condition, (ii) Superplastic diffusion-bonding of metal foams, (iii) Superplastic forming and foaming and (iv) Superplastic Zn-22Al alloy foam for energy absorbing material.