Thin Magnesium Alloy Sheets Research Articles

Assessment in predictability of visco-plastic self-consistent model with a minimum parameter approach: Numerical investigation of plastic deformation behavior of AZ31 magnesium alloy for various loading conditions

By predicting the complex deformation mechanisms, visco-plastic self-consistent (VPSC) model has been found to be a useful tool for investigating plastic deformation behavior of magnesium alloy. The standard version of VPSC model involves a large number of adjustable parameters. Using independent arguments obtained from single tests, VPSC model with a minimum parameter approach immensely reduces the number of adjustable parameters, hence shows huge potential in simulating plastic deformation behavior of thin magnesium alloy sheet. The predictability of this new approach is thoroughly assessed in the present study. Although only the mechanical response of in-plane tension (IPT) in AZ31 magnesium alloy is applied to calibrated the corresponding material parameters, simulated results in terms of texture evolution using VPSC model with a minimum parameter approach show a relatively small difference by comparison with the predicted ones applying the standard version of VPSC model during IPT, in-plane compression (IPC), through-thickness compression (TTC), and plane strain compression (PSC), respectively. Furthermore, the corresponding activated deformation mechanisms during various deformation processes are further analyzed. With the exception of pyramidal <c+a> slip, the predicted activities of remaining deformation mechanisms are generally consistent with each other. This phenomenon is identified to be the root of minor difference in texture evolution. Moreover, the predicted activities in pyramidal <c+a> slip using VPSC model with a minimum parameter approach are relatively higher than the corresponding ones in the case with the standard version of VPSC model. However, these reported results are not beyond the maximum of published literature, and hence are acceptable when simulating various plastic deformation behavior of AZ31 magnesium alloy.

A Study for the Characteristics of Laser Welding on Over-lap Joint of Thin Magnesium Alloy Sheet

A Study for the Characteristics of Laser Welding on Over-lap Joint of Thin Magnesium Alloy Sheet

Improving the room temperature stretch formability of a Mg alloy thin sheet by pre-twinning

{10−12} tensile twins were introduced by in-plane compression in a thin magnesium alloy sheet in order to tailor the texture. The room temperature stretch formability of the pre-twinned Mg alloy sheet was remarkably improved (50%). The activation of the tensile twinning in the pre-twinned region, which can effectively accommodate the through-thickness strain during stretch forming, is assumed to be the main reason of stretch formability improvement. Numerical simulation results demonstrate that multidirectional tensile twins induced by multi-steps compression are more beneficial to improve the formability of Mg alloy sheet, compared with uni-directional twins.

Microstructure and Mechanical Properties of High Aluminum Content Magnesium Alloys Fabricated by Twin-Roll Casting Process

This paper describes the twin roll casting technology of magnesium alloys that contains relatively high weight ratio of aluminum, such as AM60, AZ91 and AZ121. The cast magnesium alloy sheets were hot-rolled in an elevated temperature to investigate the appropriate hot-rolling conditions for producing high-quality strip using a purpose-built strip-casting mill. The influences of such process parameters as materials of roll, casting temperature, and roll speed are ascertained. A simple method of predicting the convection heat transfer coefficient between casting rolls and molten metal is introduced. The microstructure of the manufactured wrought alloy sheets was observed to investigate the effects of the hot-rolling and heat-treatment conditions on crystal growth in the cast products. It is found that manufacturing thin magnesium alloy sheet was possible at a roll speed of 110m/min by a vertical type roll caster. The grain size of the manufactured wrought magnesium alloys sheet was less than 30 micrometers due to rapid solidification in the proposed process.

Tangential bending and stretching of thin magnesium alloy sheets in warm conditions

The present work aims at studying the tangential bending process (wiping) and the combined effect of a bending and stretching stress on thin (0.7 mm) magnesium alloy (AZ31) sheets when working in warm conditions. The test equipment was designed in order to heat the sheet only in the bending region and to stretch the sheet after the wiping process; it was used for investigating the parameters affecting the stretch-bending state of stress in the sheet, quite common in the stamping process. A preliminary screening analysis over a large set of process parameter was performed using a full factorial design. As a result, only the effect of the temperature, the speed and the bend radius were further investigated according to a central composite design and using the springback factor and the maximum stretching load as response variables. The present work can give useful guidelines in the warm forming of AZ31 Mg alloy sheets in terms of key process parameters, fillet radii of the equipment, material stretch-bending strength (according to temperature, bending radius and speed) and precision of the final part (springback amount).

Superplasticity in thin magnesium alloy sheets and deformation mechanism maps for magnesium alloys at elevated temperatures

Rolling processes for fabricating thin AZ61 and AZ31 alloy sheets adequate for superplastic forming have been developed. Superplastic behavior of the sheets was evaluated in the temperature range 573–693 K and compared that of the initial materials having relatively coarse grains. Existing deformation mechanism maps for face-centered cubic and body-centered cubic metals were reviewed and found to be deficient in predicting the deformation behavior of magnesium alloys with hexagonal close-packed crystal structure. Using the experimental data for a number of Mg alloys, which are associated with various deformation mechanisms competing at elevated temperatures, deformation mechanism maps for Mg alloys could be constructed. Excellent prediction capability of the maps was verified at temperatures of 573–673 K.

Prevention of Corrosion in Naval Aircraft. Part I of Two Parts

Corrosion prevention of aircraft starts with proper design, proper selection of materials and control of fabrication processes. Free drainage, avoidance of dissimilar metal contacts, electrochemical insulation, proper heat treatment and cleanliness are stressed. Water contact, essential to common corrosion, is prevented or de-activated by chemical surface treatments, plating, organic coatings, preservative compounds, dehydration, hermetic sealing or other waterproofing techniques. Sacrificial protection, where advantageous, is provided by cladding, plated surfaces and readily replaceable parts such as washers. Special consideration is given to stress corrosion cracking, thin magnesium alloy sheets, engine cylinders and other internal engine parts, compressor housings, propeller shafts and other operating mechanisms where routine treatment is not practicable. Use of cadmium-tin plating, porous chromium plating, nickel plating, phenolic resin coating and phosphate treatments have given good results in these...