1 No Spac.... Heading 1 Heading 3 Title Subtitle Subtle Em... Emphasis Intense E
ID: 1718951 • Letter: 1
Question
1 No Spac.... Heading 1 Heading 3 Title Subtitle Subtle Em... Emphasis Intense E.. Styles old work uick questions (0.5 points each) 1) Strain hardening occurs because the number of (point defects / dislocations/ grain boundaries) goes up dramatically 2) When a material that originally has equiaxed, or randomly oriented, grains, is cold worked it is expected that the mechanical properties will become more (isotropic/ anisotropic) 3) Cold working typically (increases / decreases / doesn't affect) the level of residual stresses within a material. 4) During the recovery stage of annealing of a cold worked metal, the % elongation (increases / decreases is unchanged) growth) step of annealing. stress, you expect the assembly to fail in the (fusion zone (weld) / heat affected zone/ 5) The grain size is significanty reduced during the (recovery / recrystallization/ grain 6) When you weld a cold worked material, and then subjeet the welded assembly to high unaffected base metal). 7) The surface finish of a metal is expected to be better when the metal is shaped by (cold/ hot) working. 8) The dimensional accuracy of a metal part is expected to be more precise whea the metal is shaped by (cold /hot) working.Explanation / Answer
(1)
Strain hardening refers to the number of strengthening of a metal by plastic deformation. This strengthening is due to the dislocation movement within the crystal. Generally, non-brittle materials with high melting points and polymers are strengthened by strain hardening.
(2)
On cold working of a material with equiaxed or randomly oriented grains, small grains or dendrites that are formed will torn apart due to the strong convection currents that are set up due to freezing. They provide heterogeneous sites for the growth of relatively round, equiaxed, or random grains with different orientation. They stop the further growth of columnar grains thereby enhancing isotropic behaviour of material. Thus, the casting upon cooling exhibits isotropic behaviour..
(3)
Cold working typically increases the level of residual stresses within a material. This is due to the dislocation caused in the material due to cold working.
(4)
During the recovery phase of annealing, the internal stresses are due to cold work are reduced, with loss of strength and recovery of some ductility. Thus, during this phase the percentage elongation increases.
(5)
During recrystallization stage, nw unstrained nuclei are formed and they impinge on each other to form new recrystallzation grain structure.
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