Effects of boron on the deformation behavior of Ni₃Al

Abstract

The effects of boron additions (0 to 4000 wppm B) on the room temperature deformation behavior of Ni-24Al have been examined with both quasi-static deformation and short pulse duration shock loading. Changes in compressive yield strength and hardness with the amount of boron suggest that strengthening effects are more complicated than predicted by usual interstitial solid-solution strengthening considerations. The nature of the dislocations changes from SISF-dissociated superdislocations in the Ni-24Al base alloy to APB-dissociated dislocations with the additions of small amounts of boron. Therefore, the observed variation in strength with boron additions reflects a solid-solution strengthening contribution from the interstitial boron coupled with a “softening” effect arising from the greater mobility of the APB-bounding partials relative to the SISF-bounding partials. It is suggested that this “softening” is a necessary prerequisite for enhanced ductility in Ni3Al. In addition, the grain boundary fracture strength must be increased by boron additions. While this may occur through an increased grain boundary cohesive strength due to boron segregation, it is also expected that the interaction of the dislocations with the grain boundaries will be significantly altered as the nature of the dislocations changes. The lack of a “boron effect” in Ni-25Al, the so-called stoichiometric effect, can be attributed to a diminished “softening”, combined with the rapid solid-solution strengthening observed in this alloy.

Simultaneous Enhancement of the Thermoelectric and Mechanical Performance in One-Step Sintered n-Type Bi2Te3-Based Alloys via a Facile MgB2 Doping Strategy

“…Besides the powder metallurgy process, ,, adding intrinsic high-mechanical-strength nanoparticles like nano-SiC in the Bi 2 Te 3 -based alloys has also been reported to enhance their mechanical performance. , Generally, metal borides possess remarkable intrinsic mechanical properties especially the super hardness, and adding a small amount of boron in various alloys can also greatly improve their mechanical strength. − MgB 2 is one of the most popular metal borides because of its superconducting properties, which may be peculiar for tuning the thermoelectric properties of Bi 2 Te 3 -based alloys. In this work, a slight amount of MgB 2 is doped in the n-type Bi 2 Te 2.7 Se 0.3 alloys to suppress the donor-like effect from the spark-plasma-sintering process and to concurrently increase the hardness.…”

Annealing Twinning in Boron-Doped Ni<SUB>3</SUB>Al

“…This result suggests that boron is an effective element to eliminate the annealing twins. Brusso and Mikkola 27) had also obtained a similar result that boron addition greatly reduces the number of annealing twins in recrystallized Ni-24Al alloy.…”

“…The remarkable effect of boron addition on eliminating annealing twins observed in experiment supports the asymmetrical twinning in boron-doped Ni 3 Al where boron atoms act as a potent obstacle to twinning and generation of SISFs or movement of 1/3 211 superpartial dislocations. Baker et al 40) showed a trace of boron addition makes SISFs disappear in Ni 3 Ga. Brusso and Mikkola 27) reported that addition of boron decreases the frequency of annealing twinning events in Ni-24Al after heavy deformation and recrystallization.…”

“…Strongly ordered Ni 3 Al alloys [9][10][11] and Ni 3 Al-based alloys added with Ti, 10) 3 Ti where M=Mn, Cr, Co, Nb, Rh, Pd, Ag, W, Pt and Au. 22) It is noted that boron decreases the frequency of occurrence of annealing twins in Ni 3 Al [23][24][25][26][27] and Ni 3 Ga. 28) On the other hand, no information about the effect of stoichiometry can be obtained. The present study aims to investigate the effects of alloy composition and annealing temperature on annealing twinning in L1 2 Ni 3 Al.…”