Question

19. By reducing the grain size, the strength of materials increases. This is because (a) The amount of grain boundary decreases and any dislocation motion requires only a short distance before encountering a grain boundary. (b) The amount of grain boundary increases and dislocation motion requires a long distance before encountering a grain bound (c) The amount of grain boundary increases and dislocation motion requires a short distance before encountering a grain boundary (d) None of the above.

Answer 1

a th aroin sige ie grain dia metery, -the total Lnndag area aill be inc.Y e ase. . "The gram re ducinj the arain sige e arin tuso undag Yesicts "the clislocatien motion 갱 orie ntetion, -the distocation moves fren one to another, it tilt have to chage its dir twhich will be difficult. As the grain sige hage its direction the arain size Crysbello gsaphic misoriertation incresses cind obviousls distance for distocotion mstion edues and dislocation coill ses more frequently fthe arain boumdr T tomic dinor der aiin a gain bounderg eg The a cuitl result with a discontinuity of slip plane m one grain into on, other, "There "fere oftime) is cmveeb The amountf 3r ain boundanyin ilocation motion equives a short distan an counterina hounda incresses and stance be fore