Sheets
Plates / Billets / Rods

Sheets:

AMTS monitors and spots all suppliers of industrial magnesium sheets, which are rather scarce.
We also have in stock significant amount of sheets in different thicknesses (see wrought alloys properties).

Before we start using new alloys or new source for a process we examine thoroughly the sheet properties, such as:
σ_y/UTS ratio, homogenous elongation, anisotropy values, strain herdening exponent, strain rate sensitivity and multi-directional behavior test - analysis
of forming limit diagram, cup test and superplastic behavior.

Due to the Hexagonal Close-Packed (HCP) structure of the magnesium crystal, it has very poor plasticity at room temperature but quite good formability
at teperature range of 200°C to 350°C. The thermal dislocations system activates when temperature reaches 220°C.
We also investigate the superplastic formability of magnesium sheets while the main topics are the effects of microstructure (particularly grain size).

Alloys: Suitable alloys for drawing of magnesium sheets, which presently appear in the literature, are:
AZ31B-O, AZ61A, HK31A-O, HM21A-T8, ZA10-O (definitions according to ASTM B 275).

Typical values:

Yet, there are no formal values of anisotrpy coefficient (r) and strain herdening coefficient (n) for magnesium alloys. Those are super-relevant parameters for deep drawing and stretch forming processes.
Vertical anisotropy [r=j/j (thickness/width)] is measured in simple tensile tests by finding the logarithmic strain in each direction.
Average anisotropy of r > 1 is a key factor as long as causing good material flow out of the sheet plane and provides relatively small thickness reduction.
Strain hardening exponent (n) equals to the material flow curve gradient in a logarithmic presentation. This exponent measures the strength increase.
High n coefficient reduces the local strain concentration in case of tensile stresses and therefore leads to high elongation and maximum formability in stretch forming process.
It is advisable to mention that test direction (rolling or other directions) affects anisotropy results. On the other hand directionality has less effect on strain hardening coefficient (n).

Forming limit diagram analysis:

 This examination process is done by specimen test of typical sheets from different alloys.
The examination goal is to create a failure limit curve of the bi-directional plane strains.

 Major deformation in deep drawing process occurs by plain stress. The strain percentage is limited as dependency in the activated stress along each axis as well as the anisotrpy coefficient (which very much depends on sheet rolling procedure).

Cup test:

The goal in cup testing is to examine the feedstock behavior in a lab-scale deep drawing process for given criterions, such as blankholder pressure, deformation rate, temperature and lubrication.
The typical criterion for evaluating suitabilness of magnesium sheet to a deep drawing process is the drawing ratio (D/d) in a pre-failure state. Additionally, cup test can give idea about plane anisotropy (rolling direction - transverse direction plane) of the sheet.
On the other hand, during the recent development processes at AMTS, we use cup test results to fit new lubricants.

Superplasic behavior:

Superplasticity is the ability of some materials to develop very large tensile elongations (up to hundreds and thousands percents) without necking. There are several requirements for a material to be able to exhibit superplasticity:

• Fine and equiaxed microstructure (grain size generally < 10 µm)
• Grains stable under high temperature: Temperature higher than 0.4 Tm (absolute melting point)
• Strain rate sensitivity exponent) M)

When we examine the suitability of magnesium sheet to SPF process we run several procedures:

• We test tensile samples in a certain temperature range and in different strain rates.
• We examine microstructure to identify pre-process grain size.
• We run small scale multi-directional stretching process.

So far we examined in AMTS the following alloys: AZ31B, ZK10, MA20.

Using the experimental data for a number of magnesium alloys, which are associated with various deformation mechanisms competing at elevated temperatures, deformation mechanism maps for magnesium alloys were constructed. Excellent prediction capability of the maps was verified at temperatures of 573–673°K.

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Plates / Billets / Rods:

AMTS monitors and spots all sources of industrial magnesium rolled plates and extrusions, which are rather scarce.
We also hold in a quite big stock, rolled plates and extruded bars in different sizes.

Properties and material behavior:
For optimal forging, the control of feedstock parameters beyond alloy composition should be the key. Principle of these is the control of microstructure properties such as grain size and the distribution of second phase particles. Within an alloy type such as AZ80 or ZK60, wide vvariation of these aspects can be achieved, resulting in wide variation in the suitability for Forging.

• Very high strength magnesium base billets out of combination of TECHNION patented alloying and rapid solidification process.

• Magnesium billets with High deformation ratio at relatively low temperatures: by modification of conventional alloys (such as ZK60) into thixotrophic structure.

• Under research: for high temperatures (up to 150°C) applications by MMC.

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