A combination of stringent legislation on carbon emissions and fierce competition are causing rapid changes across the automotive supply chain. As CO2 emissions fall by 8.5g per 100km for each 100kg lost, cutting vehicle weight remains high on the agenda. Manufacturers are striving to get more out of every drop of fuel and, for EVs (electric vehicles), from a single charge.
The answer for manufacturers is to reduce weight by using lighter components across the entire vehicle, no matter which powertrain technology you are working with, and by replacing steel with lighter materials makes the most difference. However, the road towards light-weighting brings crucial materials analysis and quality control challenges.
There are four key technologies for materials analysis: laser induced breakdown spectroscopy (LIBS), optical emission spectroscopy (OES), thermal analysis (TA) and X-ray fluorescence (XRF). OES, XRF and LIBS are all quite versatile, particularly when it comes to identifying metals and quality checking. TA on the other hand studies the properties of materials as they change temperature.
Here we consider how these technologies are enabling the industry to ensure materials meet quality requirements.
The driving force behind change
The big driver behind automotive evolution is the environment. Current legislation aimed at reducing emissions is propelling innovation in the materials used for car components and, as global standards get more stringent, the pace of change is quickening.
European emissions standards have become more challenging in a move to combat increased pollution. Under the current regulation, Euro 6, we’re about to enter the next phase of standards, where average CO2 emissions of new cars must be a maximum of 95g/km by 2021. Moreover, the EU set CO2 emissions reduction targets of 15% by 2025 and 37.5% by 2030. This has resulted in most manufacturers developing electric powertrain technology and striving to reduce weight.
The World Harmonised Light Vehicle Testing Procedure (WLTP) came into effect in 2018 to make sure that new cars are meeting the Euro 6 standard; and is designed to reflect real driving conditions when assessing CO2 emissions.
In China, standards have also been getting stricter. China 6a, compliant with European emission standards, is set to come into force in 2020, with a further standard due in 2023. The standards will be verified under the WLTP and the target is to reduce CO2 emissions by over 90%. Similarly, with 75% of carbon monoxide pollution in the USA attributed to motor vehicles, the Environmental Protection Agency announced in January 2020 that it’s working on new rules to decrease vehicle emissions and cars are set to get lighter, following the global example.
The automotive industry and its supply chain, therefore, need to work collaboratively to deliver materials innovations to the industry to make cars lighter.
Use of lighter-weight metals on the rise
The automotive industry has very exacting requirements for components. Safety is obviously a priority and many components must be ductile to absorb energy on impact, while other parts must have strength to maintain structural rigidity.
The development of new alloys is a very exact science and analysing the melt chemistry down to the ppm level is crucial to avoid residual elements, which can impact on the properties of the alloy. Aluminium and magnesium alloys have won favour in the industry because they are light, relatively low cost and give many of the properties needed. They can be formed into complex shapes including engine components, gearbox housings and structural parts. In fact, the global market for these parts is predicted to grow at a CAGR of almost 7% to a market size of $48 billion by 2021.
Assessing aluminium
The automotive industry will make up a quarter of all aluminium consumption (30 million tonnes) by 2025 and the average car will contain almost 100kg of aluminium replacing, heavier parts.
Alongside this, a new generation of Al-Li alloys is emerging; which could become integral to various components, combining low density, strength, stiffness and damage tolerance.
To improve strength, lithium is often added, whereas phosphorus and sulphur improves machineability, but these can have a detrimental effect on corrosion resistance, so must be added in small amounts.
As aluminium is enhanced, technologies are developing to provide effective materials analysis and enable manufacturers to improve quality control. Analysers should feature a high-performance spectrometer that enables the measurement of lithium in aluminium alloys and should be capable of measuring boron-aluminium alloys, which cannot be measured with any handheld XRF analyser. The preferred choice is a handheld LIBS analysers, whilst OES offers high level analysis, idenfitying Li in Al, down to 0.0005%, as well as boron, phosphorus and sulphur.
Magnesium
Lighter than aluminium, magnesium has the highest strength to weight ratio of all structural metals. Abundant and easily recyclable, it has replaced steel and aluminium in some components and is used extensively in alloys.
Although magnesium is brittle and doesn’t have the creep resistance of aluminium, innovations could resolve that problem. Researchers can alter the microstructure of magnesium so it can be compressed at room temperature without cracking, and can also improve its energy absorption and ductility.
For analysis of alloys to the ppm level, OES technology gives the most precise results. The new generation of OES analysers combine state-of-the-art semiconductor detectors and a new optical concept for fast, reliable and cost-effective analysis of all main alloying elements; and identification of exceptionally low levels of tramp, trace and treatment elements.
Return of steel
Many steelmakers are developing a super-lightweight steel that is stronger, cheaper and almost as lightweight as aluminium in a bid to regain market share. It’s going to be hard to resist the allure of greater strength and lower cost, and with new products expected on the market in 2021.
In five years, it’s likely that vehicles will use a larger range of materials than ever before. Therefore, the need to use the right material for the right component and verification of material grade composition will be paramount.
Many foundries already use an analyser at the time of dispatch. Inspection when raw materials arrive and then again on the factory floor is equally valuable. It is becoming increasingly important to ensure teams have tools such as handheld XRF and LIBS or high performance OES on hand for materials analysis and quality checking to verify material grades before raw materials enter the production stream.
Composites as an alternative
30% lighter than aluminium and 25% the weight of steel, using composites is another route to reduce weight and improve fuel economy in cars. Their durability and ability to be moulded into variety of complex shapes without the need for high-pressure tools brings improved production efficiency and reduced costs.
Virtually all Thermal Analysis (TA) techniques can be used for quality control, and research and development within the automotive industry. Typically, DCS analysers are used for glass transition, crystallisation behaviour, reaction enthalpies and kinetics, and the influence of fillers; TMA analysers study the expansion or shrinkage of materials; and DMA analysers are best used for characterising the frequency, force and amplitude-dependent mechanical behaviour of materials.
The road ahead
The pace of industry innovation brings crucial quality control challenges across the automotive supply chain and, in response, the field of materials analysis has been rapidly changing. The continued development and application of technologies like OES, XRF, LIBS and TA is making analysis easier, with huge potential to unlock commercial value. Choosing the right technologies for every stage of the automotive development process is critical to ensure analysis keeps up with changing regulatory demands. Continued innovation and development is vital to help the automotive industry meet current and future challenges.
About the author
Mikko Järvikivi is the Head of Global Product Management at Hitachi High-Tech Analytical Science. With 15 years experience in material analysis and handheld instruments, Mikko holds a M.Sc (Tech.) in Chemical Engineering from Aalto University in Finland.
