Q1: It is possible to form martensite

ANS:D - only in iron based alloys.

It is possible to form martensite:

1. Sometimes by cold working: Cold working involves deforming a material at room temperature or slightly elevated temperatures. In some cases, cold working can induce the transformation of austenite into martensite due to the significant deformation and associated strain energy. This is known as strain-induced martensite.
2. Sometimes without nucleation: Martensite transformation does not require nucleation and growth, unlike other phase transformations like pearlite or bainite formation. Instead, martensite forms by a diffusionless transformation mechanism, where the rearrangement of atoms occurs rapidly without the need for nucleation sites.
3. Sometimes by gas quenching: Martensite can be formed by rapid cooling from austenite phase to below the martensite start temperature (Ms) through quenching. Gas quenching is one of the methods used for rapid cooling, where the material is cooled by exposing it to a stream of gas, such as nitrogen or helium, at a controlled rate. This method is often used in heat treatment processes to achieve desired material properties.
4. Not only in iron-based alloys: While martensite formation is commonly associated with iron-based alloys, it can also occur in other metals and alloys, including steels, aluminum alloys, titanium alloys, and nickel-based alloys, depending on their composition and processing conditions.