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Industry Terminology

AGING – Changes in properties of certain metals and alloys occurring at ambient or moderately elevated temperatures after hot working or a heat treatment.

ANNEALING – A term that refers to softening metals by treating with sustained heat at the required temperature, followed by cooling at a controlled rate, while at the same time, producing desired results in other properties or microstructure. Annealing generally refers to slow cooling in aluminum alloys, with the focus usually being on removing stresses; inducing softness; altering ductility, toughness, electric, magnetic or other physical and mechanical properties; changing the crystalline structure, and finally producing a definite microstructure.

HARDENING – Heating and quenching of certain aluminum based alloys from above the critical temperature range to produce a superior hardness.

HARDNESS – The ability of a metal to resist penetration. The principle methods of determining hardness of aluminum are the Rockwell Rb & Rf Scale, along with the use of Electrical Conductivity testing.

HEAT TREATMENT – The heating and cooling of metals or alloys in the solid state for the purpose of obtaining certain desirable conditions or properties.

NORMALIZING – Heating ferrous alloys to approximately 100° F above the critical temperature range, followed by cooling in air, and is used to undo previous heat treating results so as to achieve a uniform grain structure.

QUENCHING – Heating materials to the proper temperature, and holding at that temperature until the desired change in crystalline structure is achieved, followed by quenching in a water, air etc. After quenching, the materials are reheated to a predetermined temperature below the

ROCKWELL HARDNESS – A test performed on a Rockwell hardness testing machine to determine hardness.

SUB-CRITICAL ANNEALING – Also known as Stress Relief Annealing, this procedure is used to relieve stresses. Parts are uniformly heated to 1100° F., and either air cooled or slow cooled from based on the type of part being treated, and subsequent operations to be performed.


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Textron Defense Systems
TDS sincerely congratulates Modern Metal Processing for the quality of your efforts and for your clearly demonstrated subject matter expertise. In addition TDS is very grateful for MMPI’s responsiveness and execution relative to the communicated schedule urgency. TDS has determined that MMPI has diligently satisfied all of the Purchase Order requirements, with excellence. TDS looks forward to employing MMPI and your aluminum brazing expertise in the future. Very truly yours,
Paul PerrySr. Manager, Production and Development SubcontractsTextron Defense SystemsWilmington, MA