Temperature and the environment play a big role in how strong and tough different materials are. Two important properties affected by these factors are toughness and hardness.

Effects of Temperature

1. Toughness:

   • Toughness is how well a material can absorb energy and change shape without breaking. In general, when the temperature goes up, metals tend to become tougher. For example, steel behaves differently depending on the temperature. It can be tough at warmer temperatures, usually above what's called the ductile-brittle transition temperature, which can range from -100°C to +100°C.

2. Hardness:

   • Hardness tells us how resistant a material is to being changed or worn down. This property can change with temperature because of how the material is put together on a small scale. For instance, when steel gets very hot, like at 600°C, it can become softer. At this temperature, its hardness might drop from 250 HV to about 200 HV.

Environmental Influences

1. Humidity and Corrosion:

   • Moisture in the air can cause rust and other forms of damage, which can make materials less tough. For example, stainless steel that's left in salty environments for a long time could lose about 30% of its toughness in just one year.

2. Temperature Cycling:

   • When materials experience changes in temperature over and over again, it can cause them to weaken. For example, aluminum alloys that go through these changing temperatures might develop tiny cracks, which can decrease their toughness by as much as 50%.

3. Phase Transformations:

   • Changes in the environment can cause materials to change their structure, affecting both hardness and toughness. For high-carbon steels, heating them to around 400°C can improve toughness while keeping their hardness around 60 HRC.

Summary

In conclusion, temperature and environment work together to influence how materials perform. It's important to understand these effects, especially in areas like building structures and making new materials, where knowing how things work under different conditions is essential.