Prakt. Met. Sonderband 46 (2014) 139 
single spark Intensity 
composition pe 
les and the tin 
/ information nn 
jh-frequency Fig. 2: spark diagrams (intensity vs. single spark number) of Ca and Al 
e and excite Coincidental peaks (red arrow) suggest presence Ca and Al in the same inclusion. 
o the single 
orithms. 
ample at the 3. PHENOMENOLOGY OF THE SPARK ABLATION 
ement in the 
luble form in The effect of a single spark is often described as a sole crater of ablated material. We 
ase when a observed that on contrary on a freshly milled sample surface each individual spark can 
spread from one to three millimetres and create several hundreds of individual ablation 
traces. The spark also preferentially attacks the protruding inclusions, rather than the 
metal matrix (Fig. 3 left and middle). It is very interesting to observe that several inclusion 
craters are produced by a single spark, meaning that the intensity collected with a single 
spark is the sum of the intensity signals generated by all the inclusions evaporated. 
sin 
10 
- « number Al 
atoms in 
matrix 
spark Fig. 3: left and middle: ablation pattern produced by one single spark on freshly 
wmber milled surface of low alloy steel sample IARM 155A. Many craters produced by 
ablating inclusions are visible (arrows). Their diameters ia, ib and ic are 35, 12 and 
6 um, respectively. bm points on an area where matrix material was ablated. Right: 
surface after 40 single sparks. Only one large crater and few smaller are visible. 
ling AlxO3 ; : I. 
ks having When several high-frequency sparks have been applied, a layer of re-melted material is 
formed, and fewer craters are visible (Fig. 3 right). A steady-state is reached with more 
suitable balance of inclusion and matrix material ablation, and the single intensities better 
correspond to the simple model, which assigns a peak to a single inclusion. In practice, 
of Al atoms two to five hundred sparks are used to reach this state. As the sparking process 
t of Al atoms progresses. inclusions will be ablated from deeper layers. 
mber of peaks 
factors he the 4. QUALITATIVE INCLUSION ANALYSIS 
irk and arising Basic Spark-DAT algorithms allow counting peaks on a given element channel (e.g. Al). In 
0 elements in a simple approximation, this number is proportional to the number of inclusions containing 
this element. Similarly other algorithms allow counting the number of peaks on an element