Aluminum Bicrystals Research Articles

Deformation texture of channel-die deformed aluminum bicrystals with S orientations

The evolution of crystal lattice orientations in two aluminum bicrystals with S orientations, during channel die compression has been studied in detail. The boundary planes of the bicrystals were parallel to the plane of compression. The textures developed in each component crystal and at the boundary between the two crystals were examined as a function of deformation. In one of the bicrystal assemblies, the initial orientations of the component crystals were found to be unstable. They rotated to a common orientation. Hence, the bicrystal boundary, initially high angle in nature, became a low angle boundary. In the other bicrystal, the initial orientations of the component crystals were found to be largely stable. Except for some minor orientation adjustments, they remained essentially in their initial orientations, and the bicrystal boundary retained its high angle misorientation. Results of theoretical analyses using a numerical model appear to explain the texture development and the behavior at the boundary of the bicrystals very satisfactorily.

Stress relaxation across the boundary in 99.999% aluminium bicrystals and the variation of relaxation strength with temperature of measurement

Anelastic creep curves of [110] symmetrical tilt boundaries with mis-orientation angles 20°, 30°, 38.9°, 50.5°, 60.0°, 70.5° and 153.4° in 99.999% aluminium bicrystals have been measured in torsion. It was found that the relaxation strength associated with the boundary decreases to zero at and below T o which has a value of about one half of the melting temperature T m of bulk aluminium. This shows the occurrence of local disordering at the boundary region around this temperature. This result conforms with the picture of boundary disordering constructed by atomic simulation studies.

TRANSFORMATION TEMPERATURE OF GRAIN BOUNDARY RELAXATION IN ALUMINIUM BICRYSTALS

Anelastic creep curves of [110] symme rical tilt boundaries with mis-orientation angles 60°and 153.4°in aluminium bicrystals has been measured in torsion. It was found that the relaxation strength associated with the boundary becomes zero below a temperature T0 which has a value of about one half of the melting temperature Tm of bulk aluminium. This shows that a perceptible change of the internal structure of the grain boundary has taken place around this temperature.

Contribution of grain boundary to tensile deformation of aluminium bicrystal

Contribution of grain boundary to tensile deformation of aluminium bicrystal

Crystallographic fatigue crack growth in incompatible Aluminum Bicrystals: Its Dependence on Secondary Slip

The secondary slip behavior ahead of crystallographic fatigue cracks and its effect on the crack growth near the grain boundaries (GBs) in $$[12\bar 1]$$ tilt nonsymmetrical aluminum bicrystals under constant cyclic stress amplitude have been systematically examined. The displacement field ahead of short crack tips near the interfaces in two specimens has been measured by using a microfiducial grid technique. It has been observed that the critical persistent slip band (PSB) ahead of a short crack tip near the GB in a middle misoriented bicrystal was able to develop as long as the primary one and resulted in a temporary stage II growth. As a longer crystal- lographic crack grew into the grain boundary affected zone (GBAZ), activation of the critical slip ahead of the crack front and crack branching along the critical PSB occurred in all groups of the aluminum bicrystals, which reveals a crucial role of the critical slip in increasing the crack opening and triggering the slip in the adjacent grain. On the other hand, cross slip became the dominant slip mode ahead of the crystallographic crack front near the GB in a bicrystal of larger misfit angles and drove the crack along the cross PSB, a steep path with a remarkably high growth rate, until it propagated into the GBAZ. The resultant stress on the secondary slip system ahead of a crack front near the interface contributed by the internal stress due to both intergranular and intragranular incompatible strain, as well as the enhanced crack tip stress, has been evaluated and rationalizes the activation of the secondary slip systems.

Crystallographic fatigue crack growth in incompatible aluminum bicrystals: Its dependence on secondary slip

The secondary slip behavior ahead of crystallographic fatigue cracks and its effect on the crack growth near the grain boundaries (GBs) in % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaamWaaeaaca% aIXaGaaGOmamaanaaabaGaaGymaaaaaiaawUfacaGLDbaaaaa!3A22! $$\left[ {12\overline 1 } \right]$$ tilt nonsymmetrical aluminum bicrystals under constant cyclic stress amplitude have been systematically examined. The displacement field ahead of short crack tips near the interfaces in two specimens has been measured by using a microfiducial grid technique. It has been observed that the critical persistent slip band (PSB) ahead of a short crack tip near the GB in a middle misoriented bicrystal was able to develop as long as the primary one and resulted in a temporary stage II growth. As a longer crystallographic crack grew into the grain boundary affected zone (GBAZ), activation of the critical slip ahead of the crack front and crack branching along the critical PSB occurred in all groups of the aluminum bicrystals, which reveals a crucial role of the critical slip in increasing the crack opening and triggering the slip in the adjacent grain. On the other hand, cross slip became the dominant slip mode ahead of the crystallographic crack front near the GB in a bicrystal of larger misfit angles and drove the crack along the cross PSB, a steep path with a remarkably high growth rate, until it propagated into the GBAZ. The resultant stress on the secondary slip system ahead of a crack front near the interface contributed by the internal stress due to both intergranular and intragranular incompatible strain, as well as the enhanced crack tip stress, has been evaluated and rationalizes the activation of the secondary slip systems.

アルミニウム双結晶の疲労寿命におよぼす結晶粒界の影響

In order to examine the effect of grain boundary on fatigue life, aluminum bicrystals with a longitudinal boundary were prepared by the Bridgman method. They were tested by a bending fatigue testing machine under the constant strain amplitude of 0.13% and cyclic frequence of 30.4Hz. The results obtained were as follows:(1) The fatigue life decreased with increasing the saturation moment, Ms, at N=103.(2) The existance of grain boundaries in aluminum bicrystals possibly shortens the fatigue life.

Recrystallization and Grain Growth in Aluminium and Copper Bicrystals

Recrystallization and Grain Growth in Aluminium and Copper Bicrystals

Grain boundary premelting in thin foils of deformed copper bicrystals

The grain boundary premelting temperature (GBPMT) T m in thin foils of 99.99 mass% copper bicrystals deformed in tension to a strain of 0.4 increased from approximately 0.5 T M up to near the bulk melting point T M with increasing oxidation time. The GBPMT T m in thin foils of the bicrystal whose grain boundary plane was parallel to active screw dislocations was lower than that to active edge dislocations. The difference between the GBPMT in 99.99 and 99.9999 mass% copper polycrystals were not so significant. The difference between the GBPMT T m(Al)[ ≑ T M(Al)] of aluminum bicrystals and the T m(Cu)[ ≑ 0.5T M(Cu)] of copper bicrystals depends upon the difference between the properties of the corresponding oxide films and would probably be related to the difference in the elastic anisotropy between them. Plastic strain would decrease the GBPMT at least in copper.

Atomistic Simulation of Void Formation in ic Metal Interconnects

ABSTRACTWe present an atomistic model to study void formation in aluminum interconnects in integrated circuit (1C) chips. Aluminum single and bicrystals were studied with various concentrations of vacancies and strain levels. It was found that either vacancies or tensile strains could lead to void formation. It will be shown that the void formation can be prevented by maintaining compressive strains in the computational cells.

Vector CTD analysis for crystallographic crack growth

This study is aimed at assessing the crystallographic growth of fatigue cracks by means of the vector crack tip displacement ( C T D ¯ ) criterion. The geometry of crack tip sliding displacements ( C T S D ¯ ) along the persistent slip bands (PSBs) ahead of the tips of crystallographic cracks in stage I, extended stage I and stage II is considered and suggests that the driving force of the cracks essentially arises from the Δ C T S D ¯ , whereas the Δ C T O D ¯ a resultant of the Δ C T S D S ¯ along the secondary PSB and the Δ C T S D P ¯ along the primary one. A three-dimensional crystallographic crack in extended stage I in an infinite anisotropic medium is modeled. For the crack with relative short slip bands in comparison with the crack length, the modulus of vector CTD and its components are deduced and shown to be dependent on the applied stress, the orientation and the elastic and plastic anisotropy of the crystal. Experimental data of crystallographic growth in aluminum bicrystals are presented and compared with the prediction by use of vector CTD criterion.

Preparation of some specific grain boundaries in aluminum for HREM studies by cold rolling and annealing

The preparation of bicrystals with an aim to study grain boundary structure by high resolution electron microscopy (HREM) requires a careful approach. Primary attention needs to be directed towards the orientations of the crystals forming a boundary so that atomic resolution images of the bicrystal can be achieved by HREM. Mader, Necker and Balluffi have reviewed the limitations of present day high resolution microscopes in resolving grain boundary structures. According to these authors, the resolution limit (information resolution limit = 0.14 nm) of such microscopes now allows most f.c.c. metallic crystals to reveal a projected point pattern along any of the , , and directions. Resolving a grain boundary structure requires simultaneous imaging of atomic columns in crystals on both sides of the boundary. For a very thin f.c.c. metallic bicrystal, a 1[degree] or less misorientation between neighboring crystals is required to achieve a simultaneous imaging of atomic columns across the interface. The [l brace]200[r brace], [l brace]220[r brace] and [l brace]111[r brace] projected line pattern of a f.c.c. metallic crystal can also be obtained with current microscopes. A misorientation of 1[degree] to 3[degree] between such planes of f.c.c metallic bicrystal can provide atomic plane resolution across themore » interface. Bicrystals meeting these criteria for HREM studies are usually prepared either by deposition of thin film on a suitable substrate or by solidification of a required orientation seeded bicrystal either by the Bridgeman technique or by the Czochralski technique. In the present work the authors investigated a relatively simple and inexpensive cross-rolling and annealing technique to obtain bicrystals of aluminum for HREM studies of grain boundary structures. A report is given of such preparation techniques for certain specific aluminum bicrystals, which were found suitable for HREM imaging.« less

The role of grain boundary compatibility in fatigue cracking of aluminium bicrystals: Li, C. and Bretheau, T. Acta Metall. Oct. 1989 37, (10), 2645–2650

The role of grain boundary compatibility in fatigue cracking of aluminium bicrystals: Li, C. and Bretheau, T. Acta Metall. Oct. 1989 37, (10), 2645–2650

The role of grain boundary compatibility in fatigue cracking of aluminum bicrystals

The effect of grain boundaries on the cyclic deformation and fatigue crack growth in aluminum bicrystals has been studied. The incompatible primary slip by the two sides of a grain boundary creates heterogeneous slips in a narrow area beside the boundary and cracks along the boundary. The area, termed as Grain Boundary Affecting Zone (GBAZ). is characteristic of heterogeneous deformation as well as internal stresses. As an extended stage I crack grows into the GBAZ under constant cyclic stress, the crack branches and splits deviating from the favorable crack path along a primary persistent slip band (PSB). at the same time, it decelerates or even stops to grow. The microstructure-sensitive growth behavior of extended stage I cracks across grain boundaries in aluminum bicrystals accompanying the crack tip sheilding in GBAZs is refered to the compatibility requirement at the boundaries.

銅双結晶の結晶粒界における再結晶粒形成

The formation of recrystallized grains at grain boundaries was examined in orientation-controlled copper bicrystals in which primary screw dislocations in one component crystal and primary edge dislocations in another were parallel to the large angle grain boundary planes. Copper bicrystals with 99.99 mass% purity were prepared by using the modified Bridgman technique. All bicrystals were pulled in tension by the strain of 3×10−1 at room temperature and annealed mainly at 623 K for 300 s under vacuum. It was found that many recrystallized grains were formed at the grain boundaries either by the 〈111〉 rotation of the deformed matrix or by the strain induced boundary migration (SIBM). Twin-relationships were mainly observed between the deformed matrix and recrystallized grains, and occasionally between recrystallized grains. The relationships were more prominent in the copper bicrystals with the lower stacking fault energy than in the aluminum bicrystals with the higher one. The ratio of the recrystallization temperature at the grain boundary to the melting point, TRe⁄TM, was approximately 0.46 in the present study while 0.81-0.85 in the previous study in aluminum bicrystals. The ratio in the copper bicrystals is only half of that in the aluminum bicrystals. The present study supports the conclusion generally accepted that recrystallized grains form preferentially at grain boundaries by two mechanisms, namely, the 〈111〉 rotation and the SIBM in intermediately deformed fcc pure metals. The heavy pile-up of screw dislocations at grain boundaries promotes the 〈111〉 rotation, while that of edge dislocations promotes the SIBM. In the case of the 〈111〉 rotation, the twinning is more prominent with lowering stacking fault energy.

Molecular Dynamics Simulation of a ∑ = 5 Aluminum Bicrystal

A constant pressure molecular-dynamics technique is used to simulate aluminum bicrystals. The ion-ion pair potential is obtained from second order pseudopotential theory and is explicitly electron density dependent. The total cohesive energy of a metal also includes a structurally independent term which is electron density dependent. The density dependence of the total cohesive energy is carried through in the lagrangian equations of motion, so the dynamics of the simulation explicitly contains global density dependence. The simulation is at constant pressure and temperature. Temperatures up to the bulk melting point are explored in a ∑=5 symmetric tilt aluminum bicrystal.

Recrystallization of aluminum bicrystals with A [formula omitted] twist grain boundary

Recrystallization of aluminum bicrystals with A [formula omitted] twist grain boundary

Recrystallization of aluminum bicrystals with 〈211〉 tilt grain boundaries

Recrystallization of aluminum bicrystals with 〈211〉 tilt grain boundaries

Recrystallization of aluminum bicrystals with a common 7 π/45 radian {111} twist grain boundary

Etude de la recristallisation ayant lieu a des joints de grains {111} de bicristaux d'Al. Meilleure recristallisation a ces joints de grains lorsqu'ils sont deformes. Determination des relations d'orientation entre grains nouveaux et phase parent. Difference de densite des grains entre les faces avant et arriere du bicristal

⟨211⟩傾角粒界をもつアルミニウム双結晶のひずみ誘起粒界移動による再結晶粒形成

⟨211⟩傾角粒界をもつアルミニウム双結晶のひずみ誘起粒界移動による再結晶粒形成