| The grain size dependence on mechanical properties of Ni₃Al-0.5 B alloys hot extruded from elemental powders was studied. Yield strength of the Ni₃Al-0.5 B decreased with increasing grain size produced by annealing at 1000℃, but weakened at higher temperatures. The reduced grain size also diminished the extent of anomalous yielding. For the range of grain size from 6 to 103㎛, the yield strength of the alloys was given by the Hall-Petch relationship, σ_y=σ_o＋ k_y·d^(-1), where n = 0.85±0.05, σ_o=420±8 MPa and k_y=2041±168 MPa·㎛^(0.85±0.05). The deviation of the relationship from n=-0.5 was explained in terms of work hardening within Lu¨ders bands and oxide dispersion hardening. Tensile elongation of the test specimens showed insignificant variation for small grain sizes but decreased moderately for the grain size larger than about 70㎛. Regardless of the grain size, all the test specimens showed predominantly ductile transgranular fracture at room temperature. |
|
