According to the increasing order of toughness, list the following materials. Pearlite, martensite, bainite, spheroidite.

Spheroidite < Pearlite < Bainite < Martensite

Explanation:

Given materials in the question:

Pearlite, martensite, bainite and spheroidite

Now,

the correct order of the increasing toughness out of the given materials is

Spheroidite < Pearlite < Bainite < Martensite

These all are the forms of steel formed by different heating and cooling processes.