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High Temperature Strain of Metals and Alloys Part 5

Tham khảo tài liệu 'high temperature strain of metals and alloys part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 56 I 4 Physical Mechanism of Strain at High Temperatures Fig. 4.11 The jog formation in a dislocation emitted by a low-angle sub-boundary. a The initial position bi are the Burgers vectors i are the unit dislocation vectors. b The same as a after changing the signs of the vectors 3 and 4. P1 and P2 are the slip planes V1 and Vz are the velocity vectors. c Dislocations with jogs after emission of the dislocation 1. The typical Burgers vectors slip planes and unit dislocation vectors have been selected for examination of sub-boundaries. The results are presented in Table 4.2. The angles b1Ệ1 and b2ĩ 2 are not equal to 90 . This means that the dislocations of both systems contain screw components. Tab. 4.2 The crystallography of low-angle sub-boundaries. Lattice Slip plane 1 2 bl Ĩ1 biii 02 2 b2 2 f.c.c. 111 90 ị 110 110 0 ị 110 110 0 60 ị 110 110 0 ị 101 101 0 60 ị 011 110 120 ị 110 011 120 60 ị 110 110 0 ị 110 011 60 b.c.c. 110 90 ị 111 ị 110 35.3 ị 111 110 35.3 73.2 ị 111 110 144.7 ị 111 121 19.5 4.7 Significance of the Stacking Faults Energy 57 4.7 Significance of the Stacking Faults Energy The processes of high-temperature strain are dependent upon the nature of a metal especially upon peculiarities of dislocations in its crystal lattice. Metals have different values of the stacking fault energy which results in a different ability to change the slip plain i.e. to climb into parallel slip plains. This difference leads to various types of macroscopic behavior at high temperature. In Ref. 24 four crept metals with face-centered crystal lattices aluminum nickel copper and silver were investigated. The subgrain misorientations were measured with the X-ray rocking method at discrete time moments. Tests were carried out at the tensile rate of 0.5MPah 1. The total dislocation density was calculated from the misorientation angles. All four metals reveal linear dependences of the misorientation angle on strain at room temperature. In Fig. 4.12 the data oftests at 0.45 Tm