Deformation by Twinning

Summary

Deformation by twinning is a fascinating process where stress, typically mechanical like pressure, is applied to a crystal structure, causing part of it to reorient and result in a symmetric form of the original crystal. Major factors influencing twinning include grain size, strain rates, energy, pressure, and temperature. Interestingly, twinning is more common at high strain rates and low temperatures, as seen when metals are formed at high rates, such as with explosive charges, often at subzero temperatures, where there's limited dislocation mobility that inhibits slip.

Highlights

• Deformation by twinning involves applying shear stress to crystal structures. 🌐
• Twinning results in a new, symmetric orientation of the crystal. 🔄
• Factors like grain size, strain rates, energy, pressure, and temperature affect twinning. 🌡️
• High strain rates and low temperatures promote twinning. ❄️
• Explosive charges and subzero temperatures are ideal conditions for twinning in metals. 💣

Key Takeaways

• Twinning can change a crystal's structure by applying shear stress. 🔄
• It's influenced by grain size, strain rates, energy, pressure, and temperature. 🌟
• High strain rates and low temperatures favor twinning. ❄️
• Metals tend to twin at high formation rates, like during explosions, especially in subzero temperatures. 💥
• Low mobility of dislocations at low temperatures inhibits slip, making twinning more likely. 🚫

Overview

Ever wondered how crystals can transform under stress? That's where deformation by twinning comes into play! This intriguing process changes the crystal's orientation into a new, symmetric form by applying a bit of shear stress—kind of like giving the crystal a twist to find a new balance. 🌟

The magic of twinning is influenced by various factors such as grain size, how fast you're straining it (strain rates), the energy involved, and of course, the pressure and temperature. Catch this: twinning loves high strain rates and chilly temperatures, which explains why you often find it happening when metals are quickly formed with explosive gusto, especially when it's really cold! ❄️💥

Why is twinning so fascinating? Because at those low, icy temperatures, the usual crystal dislocation movements that allow slipping are too sluggish to happen. This means twinning becomes the star player, reshaping the crystal structure because the easier pathways are blocked. It's like a traffic jam that leads to a detour, and twinning is the scenic route taken by the crystals. 🚫✈️

Chapters

• 00:00 - 01:00: Deformation by Twinning Deformation by twinning occurs when shear stress is applied to a crystal structure, often due to mechanical pressure. This process causes part of the crystal to undergo deformation, resulting in a new orientation and symmetry within the deformed crystal. Factors such as grain size can influence the twinning deformation.

Deformation by Twinning Transcription

• 00:00 - 00:30 deformation by twinning is a process involving sheer stress being applied onto a crystal structure the stress is usually mechanical such as pressure the formation by twinning is also a process whereby a part of a crystal under goes the formation due to Shear resulting in a new orientation of the original crystal this will result in symmetry in the deformed Crystal there are several factors influencing the by twinning grain size
• 00:30 - 01:00 strain rates taking F energy pressure and temperature in many instances twinning is favored by high strain rates and low temperatures most metals formed Twins when they formed at high rates for example when formed by explosive charges especially at subzero temperatures also at low temperatures there is a low mobility of lest dislocations which inhibit slip