4.2 A METALS AND METALLIC ALLOYS

• Techniek
• HBO
• Studiejaar 4

4.2 A METALS AND METALLIC ALLOYS

Learning Objectives

At the end of the lesson you will be able to understand the characteristics and uses of metals and metallic alloys. At the end of the lesson you will be able to explain the processes involved in modifying the physical properties of metals, including extraction, alloying, work hardening, and tempering. At the end of the lesson you will be able to describe the design criteria for superalloys and their applications. At the end of the lesson you will be able to distinguish between ferrous and non-ferrous alloys and their specific uses. At the end of the lesson you will be able to comprehend the importance of recovery and disposal of metals to reduce environmental impact.

What do you already know about metals and metallic alloys?

Characteristics of Metals

Metals are typically hard, shiny, and have good electrical and thermal conductivity. Most pure metals are not practical for use without modification due to their softness, brittleness, or chemical reactivity.

Extraction and Economic Aspects

The extraction of metals often occurs in one country with added value occurring in another. For example, iron ore is mined in Australia and shipped to China and Japan for steel production.

Grain Size and its Effects on Metal Properties

The grain size in metals affects their tensile strength, toughness, ductility, brittleness, and malleability and can be manipulated through heat treatment.

Modifying Physical Properties of Metals

Physical properties of metals can be modified through alloying, work hardening, and tempering to enhance their characteristics for specific applications.

Alloying and its Impact on Metal Properties

Alloying involves mixing metals with other metals or non-metals to increase strength and hardness but reduce malleability and ductility.

Design Criteria for Superalloys

Superalloys are designed for high-temperature applications and require high creep and oxidation resistance, making them suitable for specific industrial uses.

Recovery and Disposal of Metals

Metals and metallic alloys are recyclable, which reduces environmental impact and energy consumption. Understanding the importance of recovery and disposal is crucial for sustainable practices.

Applications of Ferrous and Non-Ferrous Alloys

Ferrous alloys contain iron and are magnetic, while non-ferrous alloys do not contain iron and have various applications ranging from construction to electronics.

Definitions

Alloy: A mixture containing at least one metal, which may include a combination of two or more metals, or a metal and a non-metal. 

Ferrous Alloy: An alloy that contains iron and is typically magnetic, used for various engineering and specialized metal products. Non-Ferrous Alloy: An alloy that does not contain iron, used for a wide range of applications including aircraft manufacture and electrical fittings. Grain Size: The size of individual grains in a crystalline structure of metal, which can be altered by heat treatment and affects the metal's properties. 

Definitions

 Work Hardening: The process of strengthening a metal through plastic deformation. 

Tempering: A heat treatment process that increases the toughness and ductility of a metal while decreasing its hardness and brittleness. 

Superalloy: An alloy that exhibits excellent mechanical strength, resistance to thermal creep deformation, good surface stability, and resistance to corrosion, suitable for high-temperature applications. 

Creep: The tendency of a metal to slowly deform permanently under long-term exposure to stress below its yield or ultimate strength, typically at high temperatures. 

Oxidation Resistance: The ability of a material to resist the direct and indirect attack of oxygen and degradation.

quizlet.com

Find images of objects made from a alloy

Write down 3 things you learned in this lesson.

Have students enter three things they learned in this lesson. With this they can indicate their own learning efficiency of this lesson.

Ask 1 question about something you haven't quite understood yet.

The students indicate here (in question form) with which part of the material they still have difficulty. For the teacher, this not only provides insight into the extent to which the students understand/master the material, but also a good starting point for the next lesson.