Effect of interstitial solutes on the strength and ductility of titanium

Microstructure and strengthening mechanism of high strength Mg–10Gd–2Y–0.5Zr alloy

Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ∼ 1 GPa, excellent ductility (∼ 60-70%) and exceptional fracture toughness (KJIc>200 MPa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening and ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. We further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip.

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Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

Effects of rare-earth elements Gd and Y on the solid solution strengthening of Mg alloys

Modelling solid solution hardening in high entropy alloys

Single crystals of magnesium containing varying amounts of In, Al, Pb and Bi in solid solution have been deformed in tension over a range of temperature between 4.2°k and 500°k. The critical resolved shear stress (CRSS) for basal slip has been examined in the light of the existing solution hardening theories. The earlier published data on Zn, Cd, Tl and Li solutes were included in arriving at a generalized solution hardening model for magnesium. The CRSS in the plateau region (above 295°k) can be described best with a C 2/3 relationship, where C is the atom fraction of solute. The strengthening mechanism was found to be one involving the interaction of solute atoms with edge dislocations. The extent of hardening is determined by the size and valency differences between the solute and the solvent. The valency term was found equivalent to the modulus interaction term of the statistical solution hardening theories. The CRSS at 0°k increases linearly with alloying at concentrations of solute above 0....

A. Akhtar

Papers

Substitutional solution hardening of magnesium single crystals