Hardening (metallurgy)

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

Plasticity-induced martensitic transformation during cyclic deformation of AISI 304L stainless steel

Abstract: Specimens of AISI 304L stainless steel were deformed cyclically at room temperature at various plastic strain amplitudes Δϵpl/2. In addition to tests at constant plastic strain amplitudes, incremental step tests were also carried out. The cyclic deformation behaviour was investigated and related to microstructural changes observed by transmission electron microscopy (TEM). At low values of the plastic strain amplitude a saturation state was reached, whereas specimens fatigued at plastic strain amplitudes Δϵpl/2 > 0.3% exhibited, after initial cyclic hardening, an extensive secondary hardening stage which persisted until fracture. The reasons for this behaviour were clarified by TEM observations. Planar dislocation arrays with faults were observed after cycling at Δϵpl/2 = 0.02%. However, martensitic phases were not found. The specimens fatigued at Δϵpl/2 = 0.5% or in the incremental step test (0.02%<Δϵpl2<0.5%) displayed cell structures with a considerably higher number of stacking faults. Moreover, deformation-induced martensitic phases were observed and identified as ϵ- and α′-martensite by electron diffraction pattern analysis.

Latent hardening in single crystals. I: Theory and experiments

Abstract: Accurate measurements of the initial yield stress on previously latent slip systems as well as a reinterpretation of widely reported experimental observations have led to a new description of single crystal hardening within the framework of the incremental (flow) theory of plasticity. Slip interactions and the history of slips are essential in explaining well-known physical phenomena such as stage II deformation and latent hardening. Guidelines for deriving the set of instantaneous hardening moduli are given in terms of inequality restrictions. Although time-independent behaviour is assumed throughout the present study, these restrictions are expected to apply as well to time-dependent creep behaviour at low to intermediate temperatures. In Part II, a complete constitutive theory is developed with analytical forms given for the instantaneous hardening moduli.

Microstructures and microhardness of an aluminum alloy and pure copper after processing by high-pressure torsion

Abstract: Experiments were conducted on an Al–3 wt.% Mg–0.2 wt.% Sc alloy and pure Cu to evaluate the effect of high-pressure torsion (HPT). The results show that very substantial grain refinement is achieved in both materials with as-strained grain sizes of ∼150 and ∼140 nm, respectively. Microhardness measurements demonstrate increases in the hardness near the edges of the disks by factors of approximately three and two over the solution-treated conditions for these two materials, respectively. It is shown in experiments on the Al–Mg–Sc alloy that no additional hardening is achieved by reversing the direction of the torsional straining during the HPT processing. In addition, experiments on pure Cu confirm that the high values of hardness are not retained when samples are subjected to short-term anneals for 15 s or 3 min at a temperature of 473 K.