What is an allotropic phase transformation?

What is an allotropic phase transformation?

Note that an allotropic transformation is a solid state phase transformation, and as such, occurs at a constant temperature during either heating or cooling. The temperatures (designated A) associated with heating contain the subscript c, which is French for chauffage, meaning heating.

Does titanium show allotropy?

Titanium undergoes an allotropic transformation at 882 °C. Below this temperature, it exhibits a hexagonal close-packed (HCP) crystal structure, known as the α phase, while at a higher temperature, it has a body-centered cubic (BCC) structure, the β phase.

Which of these are allotropic forms of titanium?

Pure titanium has two allotropic forms: β-Ti (high temperature) and α-Ti (low temperature). For equilibrium heating conditions, the low temperature α phase transforms to the high temperature β phase at 883 °C (1156K).

When some substance undergo transformation from one allotropic form to another the process is known as?

The enthalpy change that takes place when one mole of one form of an allotropic modification changes to another is called enthalpy of allotropic transformation.

When does the allotropic transformation take place in titanium?

Knowledge of these dependences is indispensable for defining correct parameters of heat treatment and hot working of titanium and its alloys (1,2). An allotropic transformation takes place between hcp Ti (α-Ti) and bcc Ti (β-Ti) around 1155K in pure Ti. Both bcc and hcp cluster models are employed for the electronic structure calculation [1].

How does an alpha beta titanium allotrope work?

The alpha-beta titanium allotrope takes some alpha and some beta forms and combines them in order to utilize the qualities of each. Alpha-beta titanium will change its properties based on the percentage of each alloy in the mixture, and the temperature at which it is formed will change the amount in the mixture.

What causes high growth rate during allotropic transformation?

The features mentioned cause mainly high growth rate of new phase nuclei during the allotropic transformation of titanium. These features have an influence on microstructure development of titanium and its alloys during heating up to temperature above allotropic transformation and following cooling.

What happens to the crystalline structure of titanium?

The unalloyed (pure) titanium crystalline structure undergoes an allotropic phase transformation from hcp (α – at lower temperature) to bcc (β – at higher temperature) by increasing the temperature up to 882°C.