Microstructure analysis
Indiscernible to the naked eye, microstructure analyses show the microscopic structures responsible for the durability and reliability of crucial materials. Whether electric motor or aircraft component – the crucial factors for quality and reliability lie in the structure of the materials.
Table of contents
What is microstructure analysis?
Microstructure analysis is an important part of materials science and an analytical method in metallography. It forms part of destructive material inspection for the quantitative and qualitative analysis of material characteristics.
Microstructure analysis permits the analysis of the structure and composition of materials at the microscopic level. This information is important for understanding material characteristics and developing new materials.
What is the difference between quantitative and qualitative microstructure analysis?
During quantitative microstructure analysis, the focus is on the description of the characteristics of individual microstructure constituents. These include the measurable characteristics such as shape, size, orientation and distribution of microstructure constituents. Qualitative analysis focuses on more detailed information about the overall structure of the microstructure. Light microscopy is often used here to draw conclusions about the total volume of a microstructure from the metallic section.
Microstructure analysis is suitable for different materials
Microstructure analysis is undertaken on numerous materials, in particular those with a microscopic structure that affects their mechanical, thermal or electrical characteristics. Typical materials are metals and metal alloys, ceramics, glass, polymers and composite materials.
Microstructure – what is it?
Microstructure refers to the inner structure and composition of materials. The microstructure of a material therefore provides information about the microscopic arrangement of its constituents. The individual microstructure constituents are separated from each other by grain and phase boundaries. This arrangement affects the mechanical, thermal and electrical characteristics of a material. Independent of the material, microstructures describe the layout and the arrangement of the constituents at the visible and microscopic level.
Microstructure types – metal, ceramic, polymer
In materials science there are numerous types of microstructure that vary depending on the type of material. In metals and alloys we find grain structures. These are individual crystalline areas whose size and arrangement depend on the metal composition used. The manufacturing process for the material also affects the characteristics of the microstructure: depending on whether the component is forged, cast or additively manufactured, the characteristics of the microstructure change. The grains grow during the solidification of the materials from the melt and interact with each other and with foreign constituents such as phases and contamination.
The significance of the characteristics of the microstructure
The characteristics of the microstructure are directly related to the mechanical and technical characteristics of materials. This means, for instance, that they have a significant influence on strength and ductility, that is the malleability of the material: small grain sizes result in a higher strength, while large grain sizes result in a greater ductility. However, these characteristics can be changed. External effects such as corrosion, heat treatment processes and mechanical effects such as forging, bending or rolling also have an effect on the microstructure.
Different microstructures: ceramics, glass and polymers
In ceramics, the crystalline structure and the presence of glass phases are of importance, while in glass materials the amorphous structures and their homogeneity are analysed in particular.
Polymers, on the other hand, have a different microstructure that depends on the arrangement of the chains and the linking of the molecules. In composite materials, a combination of two or more materials, the interaction of the different microstructures and their boundary areas is crucial. Each of these microstructures offers unique insights and contributes to the understanding of the response of the material to external effects such as loads, temperature changes and chemical reactions.
What microstructures tell us
The microstructure provides information about the specific arrangement and form of the microscopic constituents within an individual material. It includes the detailed assessment of the internal distribution, such as the arrangement of the grains, phase distribution or porosity. In this way it can provide information about the individual characteristics of specific samples. In a metallic sample, for example, the microstructure consists of individual crystalline structures, the so-called grains. These differ in their shape, size, orientation and other characteristics depending on the material and its processing. Between the grains, there may be contamination and non-metallic inclusions that can also affect the material characteristics.
Quality Analysis:
your holistic microstructure analysis by the experts
We check and assess the microstructure of your sample in relation to grain size and grain boundaries, the presence of porosity, intermetallic phases as well as non-metallic inclusions and phases. A key element of this work is correct sampling and preparation; we have the necessary equipment and expertise for this task. If necessary, we also combine microstructure analysis with further analytical methods such as spark emission spectroscopy, hardness testing or other methods to obtain a comprehensive, informative result.
Fast, reliable
measurement results
- Preparation using all common methods
- Samples obtained without the application of heat
- Determination of grain sizes and grain boundaries
- Porosity measurement
- Determination of intermetallic phases
- Identification of non-metallic inclusions and phases
- Verification of segregation
- Analysis of state of tempering and microstructure
Microstructure analysis in metallography
Microstructure analysis starts with the careful preparation of the sample. Preparation includes sampling and cutting to a manageable size, as well as grinding and polishing the workpiece to produce a smooth surface. This surface preparation is crucial in metallography to ensure that the microscopic structure of the material is clearly visible without distortion.
The most important step in microstructure analysis
The grinding and polishing process is the most important step because the macroscopic roughness of the ground surface is reduced by polishing until the sample has a reflective surface, in this way the microscopic microstructure constituents become visible in a reflected light microscope. Metallographic specimen preparation is undertaken in several steps: after the surface has been ground flat, polishing cloths or discs with very fine abrasives, mostly diamond, aluminium oxide or colloidal silicon dioxide are used.
Microstructure under the microscope: making contrasts visible
For macrostructures, as a rule a coarser ground structure is sufficient. Metallographic specimen preparation is often followed by an etching process during which chemicals are applied to the surface to accentuate the different constituents of the microstructure. These etching agents react differently with the various phases or grains in the material, as a result contrasts are produced that are visible under a microscope.
The analysis: microstructure analysis using light or electron microscope
The actual analysis is then undertaken using microscopes, a light or electron microscope like a scanning electron microscope may be used – depending on the magnification and depth of detail required. During the microscopic analysis, characteristics such as grain size, shape, distribution and possible defects such as cracks or inclusions are assessed. Here lattice defects, structures and constituents at the submicroscopic level down to the atomic level become visible. This information is crucial for understanding the mechanical characteristics of the material as well as for identifying processing or material defects.
Technical equipment at quality analysis
In our accredited test laboratory, we can draw on a large range of light and electron microscopes for microstructure analysis so we can identify even the smallest damaged areas or inclusions. For extraction and preparation, various cutting systems are available to us with which we can prepare precision sections without a heat-affected zone. Along with fully automatic grinding and cleaning processes, we have the necessary expertise and equipment to polish and etch your sample manually.
Determination of grain size using planimetry, linear intercept method and point count method
After the generation of microscopic images, the following methods are used for the analysis and quantitative evaluation of the data. We would be pleased to provide specific advice about the different analytical methods and their appropriate use.
1
Linear intercept method
In the linear intercept method, lines are drawn based on the high-resolution microscopic images. The number of intersections between these lines with different microstructure constituents is then counted and analysed. Here, microscopy permits clear depiction of the grain structures and phase boundaries, which is essential for an exact analysis.
2
Surface areas
The microscopic image of the sample is analysed to determine the surface areas of the various microstructure constituents. The measurement of the horizontal extent is termed planimetry. With the aid of microscopes, which are often equipped with image analysis software, specific areas or phases in the material can be identified and their surface areas calculated precisely.
3
Point count method
In the point count method, a grid of points is placed over the microscopic image of the sample and the contact points between the grid points and specific microstructure constituents counted. Microscopes, in particular those with digital image processing, are crucial for this type of detailed analysis.
Goal of microstructure analysis
Microstructure analysis is a crucial analytical method if the issue is to understand and improve materials. The primary goal is to obtain detailed insights into the microscopic structure of a material. This task includes the analysis of grain sizes, phase distribution, porosity and other microstructural characteristics. The analysis makes it possible to understand how these microstructures affect the mechanical, thermal and electrical characteristics of a material.
Making visible material defects, segregation and contamination
A further goal is the identification of material defects such as cracks, inclusions or segregation that could affect the performance and the reliability of the material. Microstructure analysis also contributes to quality control and process optimisation in manufacturing by helping to understand the effects on the material of processes such as forging, welding or heat treatment. It also plays a crucial role in research and development for new materials by providing fundamental insights into the relationships between the microstructure and physical characteristics, information that is imperative for the development of advanced materials with specific characteristics.
Summary: microstructure analysis
Microstructure analysis is an analytical method that permits microscopic insights into the characteristics of materials and therefore contributes to innovation and reliability in many technical and industrial sectors.
