Twin and twin interactions in titanium-aluminum intermetallic alloys

Interaction between twins and twins in titanium-aluminum intermetallic based alloys ZHANG Yong-gang, CHEN Chang-jun Department of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083 It is widely noted that it is considered to have an important influence on the plastic hardening and fracture processes. Therefore, the level of understanding of the interaction mechanism of twins and twins in titanium-aluminum-based alloys and future research directions.

Titanium-aluminum intermetallic compound-base alloys have become the most promising new high-temperature materials due to their low density, high elastic modulus and excellent high-temperature properties, and are expected to be applied in the aerospace and spacecraft power system applications. 1 Influence of titanium-aluminum-based alloys The main obstacle is the brittleness of its room temperature, so in the past 20 years, a lot of work has been done on the study of its deformation behavior and mechanism. 1 In these works, the research on the interaction between deafness and deafness has attracted widespread attention. Slip and twinning are metal plastic deformation. This activation twinning method should be used as a way to improve the plasticity of room temperature. There exists one in the face centered cubic lattice m in 1 person 1; L55NlIUM6U2lll this type of twinning operation is entirely possible; Into the two-phase formation of 1 and 2; the gold structure 1 is a lamellar structure consisting of two-phase layers of 7 and 2. In the process of deformation, slip displacement and deformation will be hindered by the interface of various layers. The role, which is bound to plasticity. Hardening and Breaking Processes Have Important Implications In this article, we summarized the related research on the mechanism of the interaction between deformation and twinning and the interaction between deformation twinning and various lamellar interfaces in 1-base alloys. Deformation Twinning and Phase Change Twinning 1.1 Twin 1 has a superlattice structure derived from a superlattice structure, 13, consisting of 1 primary layer and atomic layer alternating along the axis; Two 2-directions composed of alternately arranged 1 and atomic 121 and mountain 1 original, and 2 indirect dislocations along 2 lateral direction = 162 are similar to those in the Shockley incomplete dislocation, so that their sliding generates guilt The faulty faults along the other two directions are incompletely dislocated in the female 16121, which is not Shockley's incomplete dislocation, and its sliding is usually generated by the ordinary layer of the foundational project. The Science Science Golden 4 help item 59, 9515371 person 1 unit cell and the main slide Displacement error; the original row of 1 facets and.哎 位 位 位 位 位 位 位 位 位 位 位 位 位 位 位 位 位 位 位 众所周知 位 众所周知 众所周知 位 众所周知 众所周知 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 肖 1 克莱It also generates twins, 23, often referred to as true faults, although 16121 cups of all dislocations move the atoms to the twin symmetrical position on one side of the slide, but their atomic species occupy the wrong position. In order to obtain true breeding, twins need atomic exchange rearrangement 1 51., 1 Cambodia species 1. Can be generated by shearing in the opposite direction of 121 poisson, 2, because its shear direction corresponds to its 001 gallbladder fault in successive 0 faces. Overslide is generated, and the 2nd bit note is the sum of the general and the twins and the above real data. The interface can be viewed as a fault interface, and this type of twinned interface is an inverting domain boundary interface. The Li Sheng parameters of each horse 1 referred to as the Henson student 01. heart 1 are summarized in 1 of 36!

Twin parameters Twin crystal types Face-centered cubic twins True twins False twins Anti twins Order twins Note 5 is the twinning shear variable.

1.2 The microstructure of the phase change 7-person alloy with rich 1 in the biphase 1 alloy is composed of 7 persons 1 and 2 indentations 1 and 2 phases. Usually the organization is mainly 7 and 2 two-phase laminations. The formed lamellar structure, 3 in the two layers usually there are seven different orientation of the 7 layers, they have 3 true twins; pseudo twin twin arrows point between the atoms without twin symmetry relationship; anti-twinning; There are three kinds of twinning relations in the order of twinning arrows, namely the relationship between true twins and pseudo- twins, and the relationship between 120 helidynamic domains. They correspond to the true twins and order twins in the above twins respectively. The following deformation mechanism is convenient for discussion. With Thompson, face 7 on behalf of the body.

Then these three relationships are available.

Deformation twin interaction in 1 person 1 base alloy 2.1 Deformation Twin interaction crystallography As stated, 7 1 1 1 per plane, 1 true twin shear vector, when any 2 of 4 1 draws are external forces acting Successively under the start will be intercepted and interact. This twin interaction crystallography of twins can be used as a twin Thomson twin called the incident twin heart plus 1 bound, abbreviated as 1 because there is only 1 true twin shear vector per face, here is hit, depending on the incident twin face The direction of the intersection line with obstacles. There are two kinds of crystallographically independent interactions that throw the first kind for the intersection line parallel to the direction along the 0 direction. The barrier twinning vector; and the incident twin vector 1 are all perpendicular to the intersection line, and the two kinds of vector crystallographic upper jaws are the intersection lines parallel to the milk 181 or 5, that is, the twin vectors are incident along the 0 direction, both with the corresponding Intersection lines 5, 5 or 5, 50%, and 30 degrees. Their projections on the intersection line and the obstacle twinning vector have equal projections on their respective intersection lines, but in the opposite direction. 2.2 Incident twin shear in the interaction The transfer condition is like saying. Incidental Brignant dislocations usually cannot be transferred directly into the barrier crystals. They will first accumulate helium at the intersection line, causing stress concentration. Only these accumulated dislocations are properly decomposed. The formation of turbulent dislocations in barrier products can relax the stress, for example, the stress concentration can not pass this benefit, and the decomposition mode of the dislocations can be easily achieved as a small tetrahedron, for example, a matrix with lattice matrix. ! 5, 軎 gt, 2 Crystal mirror symmetry at the twin crystal interface 43 Obviously, the three other deformations on the one side of the crystal lattice will interact with the twin crystals. The twins that are first started are called sand barrier products. Shi 1. Abbreviation 8 D. The number of incident helium dislocations required for the dislocations it intersects should be the same, and should ensure that the height of the steps left on the interface after transfer into the barrier twins should be an integral multiple of the spacing of 1 surface; It is immovable residue dislocation. When 2 errors exist, 5 is not existent 3 is born; 120 is called Kwon Sang and Kawasaki is used; Cambodia is 8 as the basic dot matrix or 1 is inaccurate. Responded.

The dislocation reaction means that during the twinning interaction, the continuity of the interface should also be ensured. This requires that the sum of the Pyzometer vectors of the dislocations during the dislocation reaction remains unchanged. This is already implicit in Equation 1; second, all the obstacles. Both the yttrium and the lead in the substrate should have intersecting lines along the shift plane.

In addition to the geometrical conditions mentioned above, energy and stress must also be taken into consideration. The simple dip test of the dislocation's linear energy (1) lamp position 1 should be consistent with the principle of +Ranke's energy sum, ie 625 should be Yang Zhi, where the 6th-generation Bosch's Sagittal Viewpoint value, it generates the dislocation's Pb's vectorial stress component requires that the shear stress on the small dislocation should be as high as possible.

The experimental and theoretical analysis of deformation twin interactions in the 2.3741 alloy shows that because there is only one twin vector on each side, under this kind of interaction condition, the crystal plane of the obstacle twin crystal is symmetrical to the incident twin plane. . The twins of the twins are opposite to each other because of the irreversible transformation of the one-way sex, one-hundred-thousand-eighth, one-hundred-one, and one-on-one characteristics. The shear of the incident twin cannot be transferred by the twins in the disorder twins. Therefore, the main way that can only be realized by slipping is 791 arrays. In response to this reaction, the raw shear transition changes to the common dislocation 7 slip in the 001 plane in the twin crystal and the ordinary dislocation slip in the 001 plane in the matrix lattice.

The slippage in the painting was unexpected. The reason 1 is Wan He. The four dislocations are pure edge dislocations at the intersection line, and the second deformation interaction is the interaction between the second deformation observed in experiments. The shear transfer mode of the twin deformation interaction is mainly the incidence of the twin shear transformation into an obstacle. The secondary twin 9 on the plane of mirror symmetry in the twin crystal may have the reaction formula that is the secondary twin shear. Although dislocations have been observed experimentally, the existence of 4 dislocations remains to be verified by actual progress. Details are still highly controversial.

3.2 Interaction between Deformation Twins and Different Layers of 7-Layer Interacting Solid Deflection and Pseudo Twin 7 Interactions Many experimental results are clear. In many cases, the incident twin will be strongly obstructed by the pseudo twin layer, and the dislocation slip may be excited in the pseudo twin 7 layer, but the incident twin shear has so far only occurred in the larger plastic deformation 1 Experiments with the interaction between the 120-slide 7-layer tablet showed that the total deformation of the twins was terminated at 12, and the box moved at the 7-layer interface, while it turned to slip at the 120-slide 7 layer. The three interactions described earlier have been observed in experiments. In general, in the first interaction, the incident twin shears become slippery and the secondary interface is located at a distance. The dislocation reaction of the energy is a dislocation error. However, it is a pure screw dislocation and it is likely to form a bit in the interface. The experimental results of the staggered network show that the transfer of the incident twin shear in the second interaction seems to be more difficult. The reason may be that the two sides of the interface do not match each other along the intersection line. The lateral mass is completely crystallographically equivalent along the direction of the intersection line, which may make the shear transition from the entrance into the pass. It is generally observed that the twin shear turns into 120 turns, and the slip in the slice. The possible reaction is 40,000 that is 101 slip dislocation error, and 2 is a pure screw super dislocation, it is likely to form dislocations on the interface. 4 Conclusion The important method for the deformation of 7-base alloys is between them and The interaction of the 7-layers in various orientations not only affects the plastic deformation of the alloy, but also has an important influence on the hardening and fracture behavior of the alloy. Although considerable progress has been made in the study of these interaction mechanisms, it has not yet reached a level of thorough understanding. The progressive work not only needs to reveal its mechanism, but also needs to study various microstructure factors such as sheet thickness and alloy composition, as well as external factors such as the external force orientation strain rate loading mode and the thermal interaction mechanism. On this basis, the internal mechanisms of these mechanisms of action and alloy hardening and fracture are studied. Micromechanical methods are then used to analyze and simulate the mechanical behavior of the lamellar structure and to achieve control and optimization of the microstructure. Zhang Yonggang, Professor, Ph.D., Beijing University of Aeronautics and Astronautics He graduated from Beijing University of Aeronautics and Astronautics in 1982 and went to Birmingham University in the same year to study. He was awarded a doctoral degree in JP in 1986 and was drunk at the Langfang University of Aerospace. He taught and conducted lectures in Canada, Holland, France, and other sleep sciences. Cooperation.

Chen Changqi Professor and Ph.D. Supervisor of Department of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics. Graduated from Beijing University of Aeronautics and Astronautics in 1957. He has been teaching light alloy for a long time.