Metallic Powders Analysis

Metallic powders have been consistently used in powder metallurgy (PM), 3D-printing, solder for printed circuit boards, and other industries. The composition and particle size of these powders is critical for their processability and end use application. Uniform particle size facilitates homogenous melting, good interlayer bonding, improved mechanical properties and enhanced surface finish. Ebatco’s NAT Lab has a Beckman Coulter LS 13 320 Laser Diffraction Particle Size Analyzer and a Beckman Coulter Multisizer 4 which can measure particle concentration and size distribution respectively. Our SEM/EDS capabilities also allows us to analyze the microstructure and morphology of metallic powders. Lastly, we can use our STA 449 F3 Jupiter Thermal Analyzer to determine phase transformations that can occur within these metallic powders up to 1650 ºC.

Typical Experimental Results

SEM images of a fine gold powder.

Applications

For more information please read our application notes:

Microporosity Measurement of Zn-Al Casting by Quantitative Image Analysis, PDF

Instruments: Beckman Coulter LS 13 320 Laser Diffraction Particle Size Analyzer with ULM and Sonication Control Unit connected

Key Specifications:

Microporosity Measurement of Zn-Al Casting by Quantitative Image Analysis

 

With the development of computer technology, quantitative software image analysis has become feasible. Computer software can count grain and particle size, identify nonmetallic inclusions, and calculate porosity more efficiently than traditional manual methods. In this app note, the micro porosity of a Zn-Al casting is measured to demonstrate how the quantitative image analysis works.

 

Figure 1. Typical microstructure of the Zn-Al alloy

Figure 1 shows the typical microstructure of a Zn-Al alloy. The alloy is composed of a lamellar eutectic α phase (dendrite network) and a zinc-rich η phase. In cast zinc, Al can refine the grain size and form a fine equiaxed grain structure. This can improve the strength, ductility, and toughness of zinc castings. Tiny holes form between the arms of the dendritic network due to gas evolution during the solidification process. In this sample, the relatively large pores are shrinkage cavities, which are more or less fissured and cave like in shape. It is impossible to completely remove shrinkage cavities in Zn-Al castings.

In this work, pores larger than 5 µm were selected for porosity measurement. Based upon practical applications or customer requirements, different pore sizes can be selected to calculate the porosity of the casting. To determine the effects of image magnification on porosity measurement, 200X and 500X micrographs are compared. For each magnification, five random areas were selected to measure the porosity of the casting. Figure 2 shows a typical distribution of pores within the Zn-Al casting.

Figure 2. Typical porosity measurement results using 200X (left) and 500X (right) magnification. (Pore sizes less than 5 µm were excluded from statistical calculations.)

Table 1 lists the porosity measurements with 200X and 500X magnifications. Based upon the results of the image analysis software, the average pore areas measured at 200X and 500X magnifications were very similar, around 19.74 µm². The porosities (or percentage of the total image area occupied by pores) were consistent when measured at 200X and 500X magnification.

Table 1. Porosity measurement results with different magnifications

	200X Magnification		500X Magnification
area	Average size (µm2)	Percent area (%)	Average size (µm2)	Percent area (%)
area 1	19.80	0.98	17.91	1.38
area 2	18.76	1.13	21.42	1.36
area 3	23.95	1.37	24.72	0.97
area 4	18.78	0.92	20.65	1.15
area 5	17.51	0.75	13.93	0.86
average	19.76	1.03	19.72	1.15