Hardening (metallurgy)

About: Hardening (metallurgy) is a research topic. Over the lifetime, 25584 publications have been published within this topic receiving 376012 citations.

Tensile and fatigue properties of a cast aluminum alloy with Ti, Zr and V additions

Abstract: The development of aluminum alloys for automotive powertrain applications is in high demand due to the required weight reduction and fuel efficiency. The aim of this study was to evaluate the microstructure and mechanical properties of a newly developed Al–7%Si–1%Cu–0.5%Mg cast alloy with further additions of Ti, Zr and V. The microstructure of the alloys consisted of Al dendrites surrounded by Al–Si eutectic structures with Mg/Cu/Fe-containing Si particles, and contained nano-sized trialuminide precipitates in the Ti/Zr/V added alloys. The alloys had a significantly (60–87%) higher yield strength but lower ductility than A356-T6 and 319-T6 alloys. With the addition of Ti/Zr/V both monotonic and cyclic yield strengths increased, but ductility and hardening capacity decreased due to reduced dislocation storage capacity caused by stronger interactions between dislocations and trialuminide precipitates. The Zr/V-modified alloy had a longer fatigue life, and all the alloys exhibited cyclic stabilization at low strain amplitudes and cyclic hardening at higher strain amplitudes. With increasing strain amplitude, the extent of cyclic hardening increased. Both cyclic yield strength and cyclic strain hardening exponent were higher than the corresponding monotonic yield strength and strain hardening exponent, indicating that a stronger cyclic hardening ability of the alloys developed. Fatigue cracks were observed to initiate at near-surface defects, and crack propagation was mainly characterized by the formation of fatigue striations together with secondary cracks.

SANISAND-Z: zero elastic range sand plasticity model

Abstract: The theory of zero purely elastic range in stress space within the framework of bounding surface plasticity is applied to sand constitutive modelling. The yield surface shrinks to zero and becomes identical to the stress point itself, and plastic loading occurs for any direction of the stress ratio rate on which the loading and plastic strain rate directions now depend, rendering the model incrementally non-linear. The simplicity of the conceptual structure of the model is particularly attractive as it consists of only one surface, the bounding/failure surface, and the stress point itself in the stress ratio π-plane. The image stress point on the bounding surface is defined analytically in terms of the direction of the rate of the stress ratio, with the latter being inside, on, or outside the surface, so that the model can address consistently hardening, softening and critical state response. An updating scheme of the initial value of stress ratio at unloading–reloading events is proposed in order to avoi...

A single-surface yield function for geomaterials

Abstract: The article outlines a seven-parametric yield function for geomaterials such as soils and rocks. Proceeding from a geometric representation in the principal stress space, the yield surface exhibits a closed shape, thus reflecting the sensitivity of the plastic response of this type of media to hydrostatic stresses. The yield function is able to describe the effects of primary yielding, as well as of isotropic and kinematic hardening. In addition the failure envelope contains an open cone when the number of material parameters is reduced from seven to five.