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Archives for November 2015
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VAC AERO is a leading vacuum furnace manufacturer, vacuum heat treating and coatings service provider to Aerospace and high-tech industries worldwide. Vacuum Furnace Manufacturing Advanced External Quench Vacuum Furnaces for Superior Processing! VAC AERO is committed to building furnaces with the lowest cost of ownership achieved through superior design, top quality materials and high performance […]
What is a Normal, Uni-Modal Grain Size Distribution?
ASTM Test Method E 112 says it covers test methods to determine the average grain size of specimens with a uni-modal distribution of grain areas, diameters or intercept lengths. It says that these distributions are approximately log-normal. But, it does not describe how one can determine if their specimen’s grain size distribution is a uni-modal normal (Gaussian) distribution. ASTM E 1181, Standard Test Methods for Characterizing Duplex Grain Sizes, says it covers test methods to characterize grain size in products with any other distribution (other than a “single log-normal distribution of grain sizes”). But, the only example given in Appendix X2 shows the percentage of the number of intercept measurements in 38 length classes from 0 to 1 to 37 to 38 mm. Thirty eight classes is far too many to properly reveal the grain size distribution. This procedure reveals a log-normal distribution but it is not in terms of ASTM grain size numbers, which makes it less useful.
Vacuum Diffusion Bonding – by Design
Many of us who use vacuum furnaces are all too familiar with and have learned how to counteract the unintentional diffusion bonding that has been known to occur between component parts exposed to high temperatures and low vacuum levels.
By contrast, vacuum technology that has found an important niche is that of diffusion bonding by design2-6. Vacuum diffusion bonding relies on temperature, pressure, time, and (ultra low) vacuum levels to facilitate atomic exchange across the interface between the materials. The process will work on similar or dissimilar materials so long as they are in intimate contact with one another. Vacuum diffusion bonding can be performed with or without pressure being applied and with or without the assistance of a short-lived low melting point “filler metal” (i.e. “activation layers or interlayer”) to facilitate the joining process.
