Magnesium researc1.pdf

7/27/2019 Magnesium researc1.pdf

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Magnesium researchThe Magnesium Research Group was established for an IIOF project. Collaborations with the Light

Metal Research Centre and overseas universities assist the group to focus on magnesium alloy research

and creating NZ business potential.

Magnesium database

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Magnesium database

Magnesium is the third most commonly used structural metal, following steel and aluminium. Magnesium, in its

purest form, can be compared with aluminium, and is strong and light, so it is used in several high volume part

manufacturing applications, including automotive and truck components.

The second application field of magnesium is electronic devices. Due to low weight, good mechanical and electrical

properties, magnesium is widely used for manufacturing of mobile phones, laptop computers, cameras, and other

electronic components.

Historically, magnesium was one of the main aerospace construction metals and was used for German military

aircraft as early as World War I and extensively for German aircraft in World War II. The Germans coined the name

'Elektron' for magnesium alloy which is still used today. Due to perceived hazards with magnesium parts in the

event of fire, the application of magnesium in the commercial aerospace industry was generally restricted to engine

related components. Currently the use of magnesium alloys in aerospace is increasing, mostly driven by the

increasing importance of fuel economy and the need to reduce weight. The development and testing of new

magnesium alloys continues.

Many attributes make the use of magnesium attractive, the most important of which has always been the light

weight, with a density only two-thirds that of aluminium and one-quarter that of steel. However, a number of other

positive attributes that may be less appreciated further enhance the benefit of magnesium use. These may be

listed as follows.

1. Strength: static and dynamic properties compare favourably with competitive materials. Specific strength isbetter than most other engineering materials or plastics. Specific stiffness is greater than all other common

engineering materials. Many alloys have better temperature stability than aluminium alloys.

2. Damping: some alloys have extremely high damping capacity. Some gravity cast alloys are used for vibrationfree platforms in metrology and satellite applications. Even commercial die cast magnesium alloys have better

damping than competitor materials such as steel or aluminium. Coupled with low weight and inertia, this

reduces vibration and resonance in moving parts, e.g. reduced noise and vibration in automotives. One

example of this is the now almost universal use of die cast magnesium alloy cores for vehicle steering wheels.
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3. Castability: most alloys have excellent castability and uniformity of properties in various section thicknessesand can be cast by all current casting processes.

4. Formability: although magnesium is relatively difficult to form at ambient temperatures, at elevatedtemperatures it can be easily rolled to plate and thin sheet or extruded, forged or pressed to intricate profiles

5. Machinability: alloys can be machined faster than any other engineering metal. Magnesium can be machineddry or with compatible standard coolants. Chips, etc., can be recycled in volume production.

6. Weldability: most alloys are weldable by conventional argon arc [metal inert gas (MIG)/ tungsten inert gas(TIG)] techniques. They are also amenable to laser welding, friction stir welding and other state of the art

techniques.

7. Corrosion: untreated magnesium is more corrosion resistant than steel in normal environments. Modern highpurity alloys have corrosion resistance comparable with conventional aluminium alloys. For more severe

environments, effective protection measures are necessary.

8. Recycling: scrap and components can be recycled to the same high purity and quality standards as primaryalloy. Long term use therefore has minimal environmental impact and significant energy savings, which arekey factors for use in transport and commercial applications

9. Availability: magnesium is the sixth most abundant element and readily exploitable. Resources are availableworldwide. Most widely used sources are magnesite (MgCO3), dolomite (MgCO3.CaCO3 ), carnallite

(KCl.MgCl2.6H2O) and various MgCl2 containing brines, including sea water, which contains ,1.1 kg m23 Mg

even before concentration. Most of these sources can be converted to magnesium leaving only non-toxic and

nonpolluting byproducts. Even minerals such as serpentine from asbestos tailings can be efficiently exploited.

TopResearch

Mg alloy developmentNew alloys of Mg-Sn, Mg-RE systems with improved creep resistance, and computer thermodynamic modelling on

new Mg alloys

Mg processing

Superplastic deformation, heat treatment and thermo-mechanical treatments to improve properties of Mg alloys.

Studies on the partial melting zone in arc welding of Mg-Al alloys.

TopCoating II

Electrochemical deposition

The electrochemical deposition on Mg and its alloys is mainly focused on the research as follows:

1.1 Electroless plating

There have been about 70 journal papers about electroless plating on Mg and its alloys since 90s. Electroless

plating is mainly focused on the Ni-P coating. The researches focus on the follows aspects:

Investigate the effects of parameters, such as temperature, time, bath stabilizers, substrate microstructureand surface state, on the Ni-P plating

Develop some novel methods so as to replace the toxic pre-treatment, such as molybdate immersion, micro-arc oxidation and zinc phosphate conversion coating
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Develop some novel methods based on two principles, such as mechanical attrition electroless plating,composite coating and zinc transition layer

The corrosion resistance of Ni-P electroless plating The wear and mechanical property of electroless coats1.2 Electro-plating

There have been about 20 journal papers about electro-plating of various materials on Mg and its alloys since 90s,including:

Electro-plating Zn and its composite coatings Electro-plating Cu and its composite coatings Electro-plating Sn and its composite coatingso Researching on the corrosion resistance of electro- plating Ni-P coatingso Researching on the wear and mechanical properties of coated specimeno Acidic Ni-P electro-plating based on some protective coatings and its corrosion resistance

2. Conversion Coatings

Conversion coating on Mg alloys has been applied for many years. It has widely been accepted as a pre-treatment

of further surface modification processes. There have been 80 journal papers since 90s with the research focusing

on following areas: Investigate effects of pH and temperature on the deposition properties of stannate chemical conversion

coatings formed on AZ91D

Develop some novel techniques to prepare environment-friendly conversion coating Employ phosphate-permanganate solution to prepare chrome-free conversion coating Investigate the structure and formation mechanism of phosphate conversion coating on die-cast AZ91D

magnesium alloy

Investigate the influence of treating temperatures on properties and performances of cerium conversioncoatings on magnesium alloys

Investigate effect of surface pretreatment by acid pickling on the density of stannate conversion coatingsformed on AZ91 D magnesium alloy

Investigate corrosion resistance of the fluoride conversion coating

Prepare the RE conversion coating Develop cerium-based conversion coating on AZ31 magnesium alloy Study vanadium-based chemical conversion coating on the corrosion resistance of magnesium alloy Study alkaline-based surface modification prior to ceramic-based cerate conversion coatings for magnesium

AZ91D

Prepare the conversion coating by a permanganate-REMS bath Investigate the growth mechanism of multi-elements complex coating Prepare the cerate conversion coating Investigate the deteriorate process of chrome-free conversion coating Prepare TiO2 coating by conversion treatment Evaluate electrochemical and surface characteristics of conversion coatings on ZM21 magnesium alloy Combine some surface technology, such as preparing nickel-phosphorus plating on AZ31 magnesium alloy

pretreated with a chemical conversion coating, and forming oxide film by anodizing and chemical conversion

coating

Investigate the application of conversion coating, such as effect of conversion coatings on bond strength ofmagnesium alloy adhesive joints


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3. Micro-arc oxidation

Micro-arc oxidation has become a systematic method to improve the corrosion resistance of Mg and its alloys.

There have been about 50 journal papers on the micro-arc oxidation (PEO) of Mg and its alloys since 90s. The

typical researches are as follows:

Prepare composite coatings, such as MgF2/ZrO2, Investigate the microstructure micro-arc oxidation layer Investigate parameters, such as oxidation time, electric parameters and processing parameters Prepare ceramic coatings in two different electrolytes Investigate the corrosion resistance of micro-arc oxidation layer Prepare some metal coatings, such as Mg-Nd coating Develop high energy micro-arc oxidation technique Further sealing or treatment of micro-arc oxidation coating Investigate tribological behavior of micro-arc oxidation coating Investigate the growth mechanism4. Ceramic PVD/CVD thin films

4.1 PVD coating on Mg and its alloys

There have been about 30 journal papers about PVD coatings on Mg and its alloys. Investigate effect of PVD coating on wear behaviour of Mg alloys Investigate characterization of ceramic PVD thin films and coatings on AZ31 magnesium alloys Galvanic corrosion properties of differently PVD-treated magnesium die cast alloy AZ91 General corrosion and galvanic corrosion properties of differently PVD treated magnesium die cast alloy AZ91 Investigate the oxidation behaviour of PVD coatings on Mg Zr alloys Investigate the mechanical properties4.2 CVD coating on Mg and its alloys

The research about CVD process on Mg and its alloys is limited.

Al coating on Mg alloys with pack cementation5. Magnetron sputtering

Magnetron sputtering technique has been limitedly applied on Mg and its alloys. There have been just 10 journal

papers about this application since 90s.

Al protective coating Surface treatment of Mg alloys Investigate the effect of bias on CrAlTiN coatings on magnesium alloy Prepare AlN coating

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Magnesium researc1.pdf