The Solidified Structure and Macrosegregation of Wedge-Shaped Titanium Castings Produced by Vertical Centrifugal Casting Process

2011 ◽  
Vol 317-319 ◽  
pp. 456-459 ◽  
Author(s):  
Shi Ping Wu ◽  
Qin Xu ◽  
Xiang Xue
Keyword(s):  
Rotational Speed ◽  
Secondary Electron ◽  
Centrifugal Casting ◽  
Casting Process ◽  
Alloy Element ◽  
Grain Sizes ◽  
Electron Line ◽  
Wedge Shape ◽  
Line Scanning ◽  
Scanning Electron

The present paper studied the as-cast structure and macrosegregation of the wedge-shaped castings produced vertical centrifugal casting process at different mould rotating speeds. The element distributions were determined by the secondary electron line scanning in the S-570SEM type scanning electron microscope (SEM) and the grain sizes of the castings were observed by the optical stereoscope. The research results show that the grain sizes increase with increasing of casting wall-thickness, but decrease with increasing of the mold rotational speed. The cooling rate is high and rotational speed is not high enough, therefore, there is slightly macrosegregation trend for the alloy element of Al and V in the wedge-shape castings.

Investigation of the Precipitation in Mg-Zr Alloys

2010 ◽  
Vol 142 ◽  
pp. 99-102 ◽  
Author(s):  
Guo Biao Lin ◽  
Zi Dong Wang ◽  
Zhong Zheng ◽  
Lai Feng Liu
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Electron Microscope ◽  
Centrifugal Casting ◽  
Casting Process ◽  
Induction Melting ◽  
Metal Mold ◽  
Transmission Electron ◽  
Scanning Electron ◽  
Zr Alloys

The Mg-Zr alloys with the Zr contents of 0.2%, 0.4%, 0.6% and 0.8% were prepared using induction melting, metal mold centrifugal casting process. The microstructures of the alloys were analyzed by scanning electron microscope, energy spectrum analysis, transmission electron microscope and their mechanical properties were also measured with tensile test. The results show that there are many micro- and nano-sized Zr-rich or Zr particles dispersed in Mg-Zr alloys. The nano-sized Zr-rich particle consists of a rectangle shaped Zr core and its surrounding Mg (Zr) solid solution shell with round exterior; a single Zr particle appears a coherent lattice relationship with matrix.

Scanning Electron Microscopy-cuticular Lesions on the Roundworm Ascaris Suum

1970 ◽  
Vol 28 ◽  
pp. 114-115
Author(s):  
P. A. Madden ◽  
W. R. Anderson
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Freeze Drying ◽  
Room Temperature ◽  
Secondary Electron ◽  
Distilled Water ◽  
Freeze Dried ◽  
Silver Paint ◽  
To Come ◽  
Scanning Electron

The intestinal roundworm of swine is pinkish in color and about the diameter of a lead pencil. Adult worms, taken from parasitized swine, frequently were observed with macroscopic lesions on their cuticule. Those possessing such lesions were rinsed in distilled water, and cylindrical segments of the affected areas were removed. Some of the segments were fixed in buffered formalin before freeze-drying; others were freeze-dried immediately. Initially, specimens were quenched in liquid freon followed by immersion in liquid nitrogen. They were then placed in ampuoles in a freezer at −45C and sublimated by vacuum until dry. After the specimens appeared dry, the freezer was allowed to come to room temperature slowly while the vacuum was maintained. The dried specimens were attached to metal pegs with conductive silver paint and placed in a vacuum evaporator on a rotating tilting stage. They were then coated by evaporating an alloy of 20% palladium and 80% gold to a thickness of approximately 300 A°. The specimens were examined by secondary electron emmission in a scanning electron microscope.

Edge Penetration Effects in the Low-Loss Electron Image in the SEM

1988 ◽  
Vol 46 ◽  
pp. 202-203
Author(s):  
Oliver C. Wells
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Beam Energy ◽  
Secondary Electron ◽  
Sharp Edge ◽  
Beam Diameter ◽  
Low Loss ◽  
Additional Information ◽  
Electron Image ◽  
Scanning Electron

The low-loss electron (LLE) image in the scanning electron microscope (SEM) is useful for the study of uncoated photoresist and some other poorly conducting specimens because it is less sensitive to specimen charging than is the secondary electron (SE) image. A second advantage can arise from a significant reduction in the width of the “penetration fringe” close to a sharp edge. Although both of these problems can also be solved by operating with a beam energy of about 1 keV, the LLE image has the advantage that it permits the use of a higher beam energy and therefore (for a given SEM) a smaller beam diameter. It is an additional attraction of the LLE image that it can be obtained simultaneously with the SE image, and this gives additional information in many cases. This paper shows the reduction in penetration effects given by the use of the LLE image.

Linewidth measurement using the low voltage SEM

1986 ◽  
Vol 44 ◽  
pp. 652-653
Author(s):  
M.G. Rosenfield
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Integrated Circuits ◽  
Secondary Electron ◽  
Low Voltage ◽  
Fabrication Process ◽  
Critical Dimensions ◽  
Linewidth Measurement ◽  
Threshold Technique ◽  
Scanning Electron

Minimum feature sizes in experimental integrated circuits are approaching 0.5 μm and below. During the fabrication process it is usually necessary to be able to non-destructively measure the critical dimensions in resist and after the various process steps. This can be accomplished using the low voltage SEM. Submicron linewidth measurement is typically done by manually measuring the SEM micrographs. Since it is desirable to make as many measurements as possible in the shortest period of time, it is important that this technique be automated.Linewidth measurement using the scanning electron microscope is not well understood. The basic intent is to measure the size of a structure from the secondary electron signal generated by that structure. Thus, it is important to understand how the actual dimension of the line being measured relates to the secondary electron signal. Since different features generate different signals, the same method of relating linewidth to signal cannot be used. For example, the peak to peak method may be used to accurately measure the linewidth of an isolated resist line; but, a threshold technique may be required for an isolated space in resist.

Charging microscopy and cathodoluminescence imaging of semi-insulating gallium arsenide

1986 ◽  
Vol 44 ◽  
pp. 816-817
Author(s):  
T.C. Sheu ◽  
S. Myhajlenko ◽  
D. Davito ◽  
J.L. Edwards ◽  
R. Roedel ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Secondary Electron ◽  
Crystal Defects ◽  
Device Performance ◽  
Gaas Wafer ◽  
Surface Charging ◽  
Gaas Substrates ◽  
Voltage Contrast ◽  
Cathodoluminescence Imaging ◽  
Scanning Electron

Liquid encapsulated Czochralski (LEC) semi-insulating (SI) GaAs has applications in integrated optics and integrated circuits. Yield and device performance is dependent on the homogeniety of the wafers. Therefore, it is important to characterise the uniformity of the GaAs substrates. In this respect, cathodoluminescence (CL) has been used to detect the presence of crystal defects and growth striations. However, when SI GaAs is examined in a scanning electron microscope (SEM), there will be a tendency for the surface to charge up. The surface charging affects the backscattered and secondary electron (SE) yield. Local variations in the surface charge will give rise to contrast (effectively voltage contrast) in the SE image. This may be associated with non-uniformities in the spatial distribution of resistivity. Wakefield et al have made use of “charging microscopy” to reveal resistivity variations across a SI GaAs wafer. In this work we report on CL imaging, the conditions used to obtain “charged” SE images and some aspects of the contrast behaviour.

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