We know that the strength of materials decreases with increasing temperature. Why unlike the other materials does the strength of Ni3Al compound increase with increasing temperature?
In another materials with increasing temperature maybe change the structure but strength reduced.
The studies indicate that the anomalous strengthening behavior in Ni3Al is primarily because of two reasons : i) exhaustion of mobile dislocation as a function of temperature, from successive relaxations and (ii) change of crystal structure from L12 to another L12 or DO22 causing a tetragonal distortion of the lattice.
Its an ordered structure, single dislocations can not pass, so they are coupled to pairs and form superdislocations. Than when the temperature rises, more slip systems are activated, which makes the superdislocation to partly go in to one system and partly stay in the old one, that makes their movement more energetically demanding - google kear-wilsdorf locking mechanism
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