Question

Most metallic materials with temperatures but metals with crystal structure display a sharp decline in impact energy when tested under decreasing crystal structure do not display this phenomenon due to presence of additional slip systems. O H.C.P. and F.C.C. B.C.Cand H.CP O OF.C.C. and B.C.C. OIV B.C.C. and F.C.C.

Answer 1

Ans - iv ) BCC and FCC

Explanation:

Impact energy is a measure of the work done to fracture a test specimen .  Metals with a face centred cubic (fcc) crystal structure do not undergo the transition and retain their ductility at low temperature. This is because fcc metals have a large number of slip systems in their crystal structure which allows dislocation slip to occur, even at very low temperature . The number of slip planes governs the movement of dislocations and this governs the ductility and the impact strength of any material. On the other hand , Metals with a body centred cubic (bcc) crystal structure often display ductile/brittle transition properties and Fracture in bcc metals occurs by brittle cleavage at low temperatures.