TAILIEUCHUNG - High Temperature Strain of Metals and Alloys Part 3

Tham khảo tài liệu 'high temperature strain of metals and alloys part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 26 I 3 Structural Parameters in High-Temperature Deformed Metals Fig. As in Fig. at the end of the steady-state stage. subgrain sizes D upper curves and in their misorientations n are presented on the same graph. Here and in all following figures each type of symbol corresponds to one crystallite of the same specimen. The initial mean size of the subgrains D is equal to pm in the primary stage of deformation it decreases to pm and then is almost unchanged during the steady-state creep. Time hours Fig. Structural parameters versus time and creep curve for nickel. Tests at temperature T 673K Tm Ơ 130MPa X 10L3p . Evolution of Structural Parameters 27 Fig. Structural parameters versus time and creep curve for copper. Tests at temperature T 610K Ơ MPa X 1 . The misorientation angle n increases from 2 to 5-7mrad. The change in n is observed during the primary stage. The smaller changes occur in the crystallite with the larger initial value of n open circles . Estimation of the dislocation density in sub-boundaries in conformity with Eq. gives a quantity of the order of 1013 m2. Subgrains and sub-boundaries are formed easily in copper Fig. and Fig. . The same result is observed under Ơ X 10 . at all temperatures the crystallites are reduced to fine cells and sub-boundaries are formed during the primary stage of creep. The value D decreases and the angle of misorientation increases. The steady-state strain occurs at almost constant mean values of both parameters. D and n depend strongly upon stress the greater the applied stress the greater the misorientation angles and the smaller the sub-boundaries dimensions. Thus the substructure is formed inside crystallites during the primary transitive stage of creep. The origin of the steady-state strain coincides with the end of the substructure formation. These peculiarities are seen well in Figs. and . 28 I 3 Structural Parameters in .

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