A Physical Approach to Grain Refinement of Wrought Mg Alloys via Solidification Control
Lead Research Organisation:
University of Portsmouth
Department Name: Faculty of Technology
Abstract
Human society is highly dependent on the Earth's climate, as climate patterns largely determine whether we will have enough food and fresh water. The gradual increase in the global temperature, due primarily to the increased amount of an undesirable gas, CO2, in the atmosphere, can cause significant climate changes. Road transport activities account for about 24% of the total man-made CO2 released to the atmosphere, and passenger cars are responsible for about 60% of these emissions. It is therefore an important issue to reduce the CO2 emissions from passenger cars in order to prevent the Earth's climate from deteriorating. One of the most efficient and easiest ways to do this, is to reduce the weight of a car so that the car will burn less petrol or diesel. Magnesium is a very light metal, in fact, some magnesium materials can be made lighter than water. On the other hand, they are still strong enough for making most of the parts used in a car. Therefore, they are very attractive to car manufacturers.Just like a sand castle that is made of many grains of sand, magnesium materials are composed of many small grains as well. The grain size in a magnesium material plays a very important role in determining whether the material is ductile or not. In general, the smaller the grain size, the more ductile the magnesium material will be. It is thus highly beneficial for magnesium materials to have a very small grain size, so that we can readily manufacture them into different shapes, such as sheet, tubes, bars, rods, etc. These forms of magnesium products are all very useful for making car parts and parts used in toys, bicycles, computers, mobile phones, televisions, etc. Unfortunately, large, thick magnesium materials normally have a coarse grain size, as a result, they are not ductile enough. Therefore, one has to use a very slow manufacturing process to make magnesium sheet, tubes, bars, rods, etc. This makes them very expensive and not many customers including most car manufacturers, are willing to use them in a large quantity. It is therefore crucial to reduce their grain size. Similar to the process of water becoming ice, solid magnesium materials start off as liquid magnesium. The change from liquid to solid is called solidification, which determines the grain size of a magnesium material. By effectively controlling the solidification process one can obtain a very fine grain size. In the past 65 years, there have been many efforts towards controlling the solidification process of magnesium materials. Although there have been some positive developments, the resultant grain size is still not small enough. In this programme, we propose a unique approach, designated 'twin-screw melt shearing'; it can effectively control the solidification of a magnesium material. The key point of this approach is to ensure that as many small grains as possible survive in the liquid during solidification. This is done by rapidly lowering the bulk liquid temperature to below a critical value; in doing so, the process will give a very fine and uniform grain size. Preliminary experiments have given very encouraging and exciting results, suggesting that the concept is feasible. Therefore it is hoped that further study into this new solidification control process will develop a hugely beneficial processing system, which will be able to deliver a fine grain size in large, thick magnesium products. It is further anticipated that the new technology will also be applicable to the solidification of other materials, such as aluminium and titanium.The anticipated results from this study will be both environmentally and economically beneficial to the global community.
People |
ORCID iD |
Nick Bennett (Principal Investigator) | |
Qian Ma (Co-Investigator) |
Description | The study proved that ultrasonic processing of Mg alloy is capable of refining grain structure in an industrial setting, but that some equipment performance limitations exist in thermal and fatigue areas. |
Exploitation Route | Further supply chain providers could develop more robust equipment. |
Sectors | Aerospace, Defence and Marine,Education,Manufacturing, including Industrial Biotechology,Transport |
Description | Test equipment set-ups have been recorded at the foundry location for future use. |
First Year Of Impact | 2010 |
Sector | Manufacturing, including Industrial Biotechology |
Impact Types | Economic |
Title | Ultrasonic Probe Equipment |
Description | Design and production of titanium probe equipment for correct frequency response, power transmission, heat flux life capability and fatigue failure resistance and threaded joint interfaces. |
Type Of Material | Improvements to research infrastructure |
Provided To Others? | No |
Impact | Several physical breakages remain unresolved. |
Description | Main and Supply Chain collaborators |
Organisation | Magnesium Elektron |
Department | Research & Technical Development |
Country | United Kingdom |
Sector | Private |
PI Contribution | The academic team and two collaborators named above brought together the application of ultrasonic equipment to the agitation of AZ91 Mg alloy in controlled industrial sample trials in a safe process control foundry location. |
Collaborator Contribution | Partners made available personnel with craft expertise, alloy samples, foundry equipment and cover gas (Mg Elektron) and an STG200 ultrasonic generator and various geometries of titanium probes. |
Impact | Further understanding of ultrasonic processing of liquid Mg alloy (materials science). Primary research into generator and probe assemblies capable of ultrasonic processing Mg alloys (advanced manufacturing processes). Limitations of ultrasonic equipment processing with respect to heat flux effects and fatigue failure. Health & Safety legislation and EU legislation on free surface SH6 gas. |
Start Year | 2008 |
Description | Main and Supply Chain collaborators |
Organisation | Sonotronic Ultrasonic Technology Ltd |
Country | United Kingdom |
Sector | Private |
PI Contribution | The academic team and two collaborators named above brought together the application of ultrasonic equipment to the agitation of AZ91 Mg alloy in controlled industrial sample trials in a safe process control foundry location. |
Collaborator Contribution | Partners made available personnel with craft expertise, alloy samples, foundry equipment and cover gas (Mg Elektron) and an STG200 ultrasonic generator and various geometries of titanium probes. |
Impact | Further understanding of ultrasonic processing of liquid Mg alloy (materials science). Primary research into generator and probe assemblies capable of ultrasonic processing Mg alloys (advanced manufacturing processes). Limitations of ultrasonic equipment processing with respect to heat flux effects and fatigue failure. Health & Safety legislation and EU legislation on free surface SH6 gas. |
Start Year | 2008 |
Description | Lectures to undergraduates |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Undergraduate students |
Results and Impact | Added to curriculum enhancement and the application of research into teaching. Lab hardware and materials samples promoted debate and questions. |
Year(s) Of Engagement Activity | 2008,2009,2010,2011 |