Creep Fracture of Aluminum and Copper Tricrystals Having 〈110〉-Tilt Σ3, 3, 9 Grain Boundaries

Abstract

The major objective of the present study was to investigate the effect of the constraint of grain-boundary sliding and its accommodation at triple junctions on the creep fracture of tricrystals. Tricrystals of pure aluminum and copper having ©110ª-tilt 3, 3, 9 boundaries were grown by the Bridgman method. Creep tests were carried out for tensile specimens in which the 9 boundary made an angle of 45°with the tensile axis at temperatures above 0.80 T M , where T M stands for the melting temperature on the absolute temperature scale. In both aluminum and copper tricrystals, dominant grain-boundary sliding occurred along the 9 boundary. The aluminum tricrystal fractured along a plane across grains, far separated from the triple junction. In contrast, the copper tricrystal fractured via a complete separation along the 9 boundary followed by a tear-off of the remaining portion. This difference is accounted for by the different local deformation behaviors around the triple junctions to release the stress concentration induced by the constraint of 9 sliding, e.g., grain-boundary sliding along the 3 boundary in aluminum and crack formation along the 9 boundary in copper.

Creep Fracture of Copper Tricrystal along Grain Boundaries

“…The formation of cavities clearly shows that ductile deformation occurred between Grains A and C at the final stage of fracturing. In a previous paper, 35) we reported that a Cu tricrystal having the same orientation as in the present study exhibited a ductile fracture within the grain that corresponds to Grain C in the present study. On the other hand, the final fracture of sample 3 occurred along the 3-2 boundary.…”

“…Particularly, only a limited number of studies have employed tricrystals having 3, 3, 9 boundaries. 3034) Recently, Okada et al 35) studied the creep deformation of aluminum (Al) and copper (Cu) tricrystals having ©110ªtilt 3, 3, 9 boundaries to compare their deformation and fracture behaviors. In Al tricrystals, grain-boundary sliding occurred not only along the 9 boundary but also along the 3 boundaries to accommodate the stress concentration at the triple junction.…”

Best Papers Awarded in 2022 by <i>Materials Transactions</i>

“…In association with the awarded papers introduced above, popular topics that Materials Transactions published in recent years are grain boundary segregation 93) as Ito et al were concerned with, 4,30,49) creep deformation in a wide range of materials 94102) including tricrystals by Okada et al 103,104) and work hardening in various forms of deformation in an aluminum single crystal, 105) an A3104 aluminum alloy, 106) a Ti6Al4V alloy 107) and high-strength steels. 108) Furthermore, pitting corrosion resistance is also a popular issue reported by many research groups in terms of corrosion behavior of pure aluminum, 109) pure zirconium 110) and stainless steels.…”