TAILIEUCHUNG - Mechanical Engineer´s Handbook P3

CHAPTER 3 ALUMINUM AND ITS ALLOYS Seymour G. Epstein J. G. Kaufman Peter Pollak The Aluminum Association, Inc. Washington, . INTRODUCTION PROPERTIESOFALUMINUM ALUMINUMALLOYS 45 45 46 ALLOYDESIGNATIONSYSTEMS 46 MECHANICAL PROPERTIES OF ALUMINUM ALLOYS WORKINGSTRESSES CHARACTERISTICS Resistance to General Corrosion Workability Weldability and Brazeability TYPICAL APPLICATIONS MACHININGALUMINUM 48 49 51 51 51 51 52 53 Cutting Tools Single-Point Tool Operations Multipoint Tool Operations CORROSION BEHAVIOR General Corrosion Pitting Corrosion Galvanic Corrosion FINISHING ALUMINUM Mechanical Finishes Chemical Finishes Electrochemical Finishes Clear Anodizing . | CHAPTER 3__ ALUMINUM AND ITS ALLOYS Seymour G. Epstein J. G. Kaufman Peter Pollak The Aluminum Association Inc. Washington . INTRODUCTION 45 Cutting Tools Single-Point Tool Operations 53 53 PROPERTIES OF ALUMINUM 45 Multipoint Tool Operations 54 CORROSION BEHAVIOR 54 ALUMINUM ALLOYS 46 General Corrosion 55 Pitting Corrosion 55 ALLOY DESIGNATION SYSTEMS 46 Galvanic Corrosion 56 MECHANICAL PROPERTIES OF FINISHING ALUMINUM 56 ALUMINUM ALLOYS 48 Mechanical Finishes 56 Chemical Finishes 56 WORKING STRESSES 49 Electrochemical Finishes 56 Clear Anodizing 57 CHARACTERISTICS 51 Color Anodizing 57 Resistance to General Integral Color Anodizing 57 Corrosion 51 Electrolytically Deposited Workability Weldability and Brazeability 51 51 Coloring Hard Anodizing Electroplating 57 57 57 TYPICAL APPLICATIONS 52 Applied Coatings 57 MACHINING ALUMINUM 53 SUMMARY 57 INTRODUCTION Aluminum is the most abundant metal and the third most abundant chemical element in the earth s crust comprising over 8 of its weight. Only oxygen and silicon are more prevalent. Yet until about 150 years ago aluminum in its metallic form was unknown to man. The reason for this is that aluminum unlike iron or copper does not exist as a metal in nature. Because of its chemical activity and its affinity for oxygen aluminum is always found combined with other elements mainly as aluminum oxide. As such it is found in nearly all clays and many minerals. Rubies and sapphires are aluminum oxide colored by trace impurities and corundum also aluminum oxide is the second hardest naturally occurring substance on earth only a diamond is harder. It was not until 1886 that scientists learned how to economically extract aluminum from aluminum oxide via electrolytic reduction. Yet in the more than 100 years since that

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