Materials A: Lecture 10- Alloys: Solid Solutions

What are alloys, and how they different from pure metals?

Alloys are mixtures of metals with other elements. They are like blends of a main metal with additional elements. For instance, steel, one of the most common alloys, is made up combining iron with carbon and other elements like chromium, nickel and molybdenum. Alloys end up with different properties compared to the original metal due to the additional element mixed in.

What significant historical events relate to the development of alloys?

Alloys have played pivotal roles in human history. During the Bronze Age, humans combined copper with tin to create bronze, a stronger and more durable metal used in tools and weapons. The Iron Age saw the development of iron alloys, while steel, discovered by the Hittites, revolutionized metalworking. Through the ages, various regions developed unique alloy-making methods. The Industrial Revolution further advanced alloy manufacturing, leading to alloys like stainless steel. In modern times, innovations in aerospace and electronics brought specialised alloys like superalloys.

What is a solid solution, and how does it affect materials?

Solid solutions form when small amounts of different elements disperse uniformly in a material. In metallic materials, the point defects created by these dispersed elements hinder dislocation movement, resulting in solid-solution strengthening, making materials stronger.

What influences the amount of an element that can be added for solid-solution strengthening?

The amount of alloying elements that can be added is limited by the solubility of the alloying element in the hose material. Factors that limit solubility include a significant atomic size difference, different crystal structures, and distinct valence and electronegativity of the alloying element compared to the host material

How does solid-solution strengthening affect the properties of metallic materials?

Solid-solution strengthening increases strength and hardness in metallic materials. However, it often reduces ductility and electrical conductivity. Nonetheless, an essential function of solid-solution strengthening is providing good high-temperature properties to the alloy.