Texture Analysis of Damascene Copper Interconnects

Texture and grain boundary character distribution of Cu interconnects with different line width for as-deposited and annealed conditions were measured by EBSD. All specimens appear mixed texture and （111） texture is the dominate component.As-deposited interconnects undergo the phenomenon of self-annealing at RT,in which some abnormally large grains are found. Lower aspect ratio of lines and anneal treatment procured larger grains and stronger （111） texture. Meanwhile, the intensity proportion of other textures with lower strain energy to （111） texture is decreased. As-deposited specimens reveal （111）（112？ and （111） （231） components, （111） （110） component appeared and （111） （112？ and （111） （231） components were developed during the annealing process. High angle boundaries are dominant in all specimens, boundaries with a misorientation of 55°-60° and ∑3 ones in higher proportion, followed by lower boundaries with a misorientation of 35°-40° and 29 boundaries. As the aspect ratio of lines and anneal treatment increase,there is a gradual in- crement in ∑3 boundaries and a decrease in ∑9 boundaries.

Effect of hot rolling on microstructure and tribology behaviors of Ti-50.8Ni alloy

We link different microstructures to tribological behaviors of Ti-50.8 Ni(mole fraction, %) in reciprocating mode at room temperature(20 ℃). Hot-rolled alloys with B2 phase exhibit lower coefficient of friction and wear rate compared to the ones with B19?. Stress-induced martensitic transformation occurs during sliding. However, multi-pass hot rolling weakens the wear resistance. In this study, microstructures were characterized through electron backscatter diffraction and transmission electron microscopy(EBSD/TEM). From the concept of energy conservation, the effects of weak intensity of hot-rolled textures on the wear resistance are minimal. Based on the result that the alloy with a higher portion of coincidence site lattice boundaries shows lower martensitic start transformation temperature in the DSC curves than that with higher KAM values, the delay on B2-B19? transformation from {112}B2 twins outweighs dislocations. Moreover, widely distributed small-angle grain boundaries owing to dynamic recovery improve the wear resistance effectively compared to those that are well-recrystallized.

Application of Grain Boundary Engineering to Improve Intergranular Corrosion Resistance in a Fe–Cr–Mn–Mo–N High-Nitrogen and Nickel-Free Austenitic Stainless Steel

Optimization of grain boundary engineering(GBE) process is explored in a Fe–20Cr–19Mn–2Mo–0.82N high-nitrogen and nickel-free austenitic stainless steel, and its intergranular corrosion(IGC) property after GBE treatment is experimentally evaluated. The proportion of low Σ coincidence site lattice(CSL) boundaries reaches 79.4% in the sample processed with 5% cold rolling and annealing at 1423 K for 72 h;there is an increase of 32.1% compared with the solution-treated sample. After grain boundary character distribution optimization, IGC performance is noticeably improved. Only Σ3 boundaries in the special boundaries are resistant to IGC under the experimental condition. The size of grain cluster enlarges with increasing fraction of low ΣCSL boundaries, and the amount of Σ3 boundaries interrupting the random boundary network increases during growth of the clusters, which is the essential reason for the improvement of IGC resistance.

Dependence of corrosion resistance on grain boundary characteristics in a high nitrogen CrMn austenitic stainless steel

Processing schedules for grain boundary engineering involving different types of cold deformation（tension, compression, and rolling） and annealing were designed and carried out for 18Mn18Cr0.6N high nitrogen austenitic stainless steel. The grain boundary characteristic distribution was obtained and characterized by electron backscatter diffraction（EBSD） analysis. The corrosion resistance of the specimens with different grain boundary characteristic distribution was examined by using potentiodynamic polarization test. The corrosion behavior of different types of boundaries after sensitization was also studied.The fraction of low-∑ boundaries decreased with increasing strain, and it was insensitive to the type of cold deformation when the engineering strain was lower than 20%. At the strain of 30%, the largest and smallest fractions of low-∑ boundaries were achieved in cold-tensioned and rolled specimens, respectively. The fraction of low-∑ boundaries increased exponentially with the increase of grain size. The proportion of low-∑ angle grain boundaries increased with decreasing grain size. Increasing the fraction of low-∑ boundaries could improve the pitting corrosion resistance for the steels with the same grain size.After sensitization, the relative corrosion resistances of low-∑ angle grain boundaries, ∑3 boundaries, and ∑9 boundaries were 100%, 95%, and 25%, respectively, while ∑27 boundaries, other low-∑ boundaries and random high-angle grain boundaries had no resistance to corrosion.

Effect of Thermomechanical Parameters on Σ3~n Grain Boundaries and Grain Boundary Networks of a New Superaustenitic Stainless Steel

Hot compression tests were conducted in a temperature range of 800--1100 ℃and strain rate range of 0. 1- 10 s^-1 using a Gleeble 3500 thermomechanical simulator to investigate the influence of hot deformation parameters （temperatures, strain rates and strains） on the grain boundary network evolution of a new grade Fe-Cr-Ni superaustenitic stainless steel. The results showed that a dominant effect of deformed temperature is ∑3^n （n = 0, 1, 2, 3） boundaries population increased with decreasing temperature, while they first increased and then reduced with in- creasing strain and strain rate. Interestingly, besides E3n （n = 1, 2, 3） twin grain boundaries, some El boundaries could interrupt grain boundaries network effectively, which enhance material performances. But they are scarcely re- ported. The misorientation of some segments LAGBs in the deformed microstructure （pancaked grains） increased and slid to high angle grain boundaries with increasing the fraction of reerystallized grains during hot deformation.

Improving Intergranular Stress Corrosion Cracking Resistance in a Fe–18Cr–17Mn–2Mo–0.85N Austenitic Stainless Steel Through Grain Boundary Character Distribution Optimization

The grain boundary character distribution(GBCD) optimization and its effect on the intergranular stress corrosion cracking(IGSCC) resistance in a cold-rolled and subsequently annealed Fe-18 Cr-17 Mn-2 Mo-0.85 N high-nitrogen nickel-free austenitic stainless steel were systematically explored.The results show that stacking faults and planar slip bands appearing at the right amount of deformation(lower than 10%) are beneficial cold-rolled microstructures to the GBCD optimization.The proportion of special boundaries gradually increases in the subsequent stages of recrystallization and grain growth,accompanying with the growth of twin-related domain in the experimental steel.In this way,the fraction of low ∑ coincidence site lattice(CSL) boundaries can reach as high as 82.85% for the specimen cold-rolled by 5% and then annealed at 1423 K for 72 h.After GBCD optimization,low ∑ CSL boundaries and the special triple junctions(J2,J3) of high proportion can greatly hinder the nitride precipitation along grain boundaries and enhance the capability for intergranular crack arrest,thus improving the IGSCC resistance of the experimental steel.