Inverted metallographic microscope is the core equipment for material microscopic analysis, designed specifically for observing the surface morphology of opaque samples with its objective lens located below the stage. The following is a detailed description of the usage standards from four aspects: preliminary preparation, operation process, key details, and maintenance:
1、 Preparation before startup
1. Environmental requirements
-Place on a stable surface, away from vibration sources (such as centrifuges) and strong electromagnetic interference equipment;
-The ambient temperature should be controlled at 20 ± 5 ℃ and the humidity should be ≤ 60% to avoid mold growth in optical components or short circuits in circuits.
2. Sample preparation
-Cutting and inlaying: Use a precision cutting machine to obtain thin sheets ≤ 10mm, and use thermosetting resin inlaying to protect the edges and make it easy to hold;
-Grinding and polishing: remove scratches with SiC sandpaper (from coarse to fine) in turn, and finally polish to mirror surface with diamond spray;
-Corrosion treatment: Select chemical reagents (such as nitric acid ethanol solution to corrode steel) according to the material type, and control the time to highlight the microstructure.
3. Instrument inspection
-Confirm that the locking screw of the objective disc has been loosened and there are no stains on the eyepiece/objective lens;
-Check if the brightness adjustment knob and filter of the light source are reset to zero position.
2、 Operation process
1. Sample installation
-Fix the prepared sample onto the stage fixture, ensuring that the observation surface is facing downwards and aligned with the objective lens;
-Lower the coarse focus knob to a low position to avoid the objective lens colliding with the sample.
2. Initial focusing
-Switch to low magnification objective lens (such as 5x), turn on halogen lamp or LED light source;
-Slowly lift the stage by coarse focusing until a blurry image appears in the field of view;
-Use fine adjustment focus to make the tissue contour clear and visible.
3. Magnification switching and observation
-Follow the principle of "from low to high" when replacing the objective lens (such as 10 × → 20 × → 50 ×), and re adjust it after each lens change;
-At high magnification, turpentine can be dripped as an immersion medium to improve resolution and reduce glare.
4. Image acquisition
-Turn off real-time preview function when connecting a digital camera to reduce noise;
-Adjust exposure time and white balance to avoid overexposure or color cast;
-Take multi area photos for subsequent puzzle analysis.
3、 Key Details
1. Selection of Bright and Dark Field Modes
-Bright field: suitable for routine tissue observation, relying on surface reflection light imaging;
-Dark field: By protruding non-metallic inclusions or small pits through a circular light path, a circular light blocking plate needs to be installed.
2. Polarized light application
-Inserting a polarizer and analyzer can eliminate stress birefringence artifacts and accurately analyze grain orientation.
3. Depth of Field Control
-At high magnification, the depth of field is extremely shallow, with a clear range of only a few micrometers, and the three-dimensional morphology can be reconstructed through Z-axis layer scanning.
4、 Precautions and Maintenance
1. Safety protection
-It is prohibited to plug in or remove the objective lens or replace the light bulb with electricity to prevent electric shock;
-When not in use for a long time, the power should be cut off and covered with a dust cover.
2. Cleaning and maintenance
-Clean the debris on the stage with a rubber blow ball daily, and lightly wipe the objective lens with lens paper dipped in anhydrous ethanol;
-Check the lubrication condition of the guide rail every month and regularly calibrate the accuracy of the stage movement.
3. Common fault handling
-Image blur: Check the flatness of the sample and the cleanliness of the objective lens;
-Flashing light source: Replace aging light bulbs or check for poor power supply connections.