Deformation-induced martensitic transformation behavior in cold-rolled and cold-drawn type 316 stainless steels

Fatigue strength assessment of butt-welded joints with undercuts

Thin-walled cylindrical specimens subjected to torsional prestraining are stress-reversed along the Bauschinger curve. The Bauschinger effect (BE), yield behavior, and flow behavior of the stress-reversed mild steel were examined by using combined loadings of axial load, internal pressure, and torsion. The results indicate that the stress-reversed steel has the same yield stress at 0.2 pct offset strain in reloading tests of forward and reverse torsion, when the reverse strain is \(\bar \varepsilon _1^p \)=0.77 pct. Furthermore, it is possible to cause the yield stresses in forward and reverse torsion to coincide in any offset strain. The yield locus of the stress-reversed steel is symmetric with respect to the tensile stress axis in a tension-torsion stress field. However, it has been found to be an anisotropy in the stress-reversed steel, and the magnitude of anisotropy is related to the offset strain. For example, there is a stronger anisotropy at 0.2 pct offset strain than at 2 pct offset strain, even though the BE is eliminated for the former. It is shown that the reduction in the BE by stress reversal is concerned with the relief of the long-range back-stress generated by prestraining. Besides, the roles of aging in the stress-aging process lie in the contributions to age hardening and development of directional back-stress.

Bauschinger effect and multiaxial yield behavior of stress-reversed mild steel

Since ω-phase crystals in β-Ti alloys formed by aging become nucleation sites of α-phase crystals due to further or high temperature aging, it is thought that this phenomenon can be utilized to produce stronger and more ductile (β+α) duplex Ti alloys. In order to form high density ω-phase crystals, the effects of a stress-aging and hydrostatic pressurizing on the formation of ω-phase crystals in Ti-20Mo and Ti-15Mo-5Zr alloys (mass%) were investigated using high resolution electron microscopy and dark field imaging methods. The results obtained are as follows: (1) An aging under a stress of a half of the yield stress promotes the precipitation of high density ω-phase crystals. (2) Hydrostatic pressurizing also promotes the formation of ω-phase crystals, and it is recognized that a hydrostatic pressure of 0.7 GPa initiates to form ω-phase crystals in a Ti-20Mo alloy.

Effect of Applied Stress on Formation of ω-Phase in β-Ti Alloys

Thermodynamic, structural and surface properties of liquid Cd–Zn alloys

X-ray Analysis on 18-8 Cr-Ni Stainless Steel

The Effect of Stress on the Process of Strain-aging of Mild Steel (Changes in Properties of Mild Steel Caused by Stress-aging Treatment, 7th Report)

Observation of Electron-microscopic Structures of Stress-aged Mild Steel

Effect of the Stress-aging Treatment on Strain-aging Behaviour of Mild Steel

Although there have been few subjects in the field of physical metallurgy which have attracted more interest and attention than that of aging phenomena of mild steel, but little study has been made so far on the effect of stress upon strain aging. Using a 0.05 wt% C steel, strain aging was carried out with and without tensile stress at temperatures ranging from 55°to 250°C. The specimen was plastically strained about 9% in elongation at room temperature prior to the aging.The rate of aging was much enhanced by the stress. However, the inherent mechanism of strain aging does not seem to have been changed by the stress, since the apparent activation energy for strain aging is not changed by the stress imposed on the specimens during the aging process.The activation energy of 16000cal/mole was obtained at temperatures below 100°C which is about the same as that for diffusion of nitrogen in alpha iron, while a rather low activation energy of 9600cal/mole was obtained at higher temperatures. This difference implies that strain aging is controled by two different kinds of thermally activated processes. The early stages of strain aging at low temperatures are considered to be associated with migration of solute atoms to dislocations. But in the later stages and at higher temperatures, strain aging is caused by the strain-induced precipitation of carbides or nitrides at dislocations.It requires considerably more studies to define the effect of stress on strain aging. However, it is considered that the stress effects the vibrational frequency of the atoms around the dislocations and increases the diffusion constant of the solute atoms so that the rate of strain aging is enhanced by the stress.

https://www.jstage.jst.go.jp/article/jsms1963/13/129/13_129_445/_pdf

Tadashi Kawasaki

Papers

X-ray Analysis on 18-8 Cr-Ni Stainless Steel

The Effect of Stress on the Process of Strain-aging of Mild Steel (Changes in Properties of Mild Steel Caused by Stress-aging Treatment, 7th Report)

Observation of Electron-microscopic Structures of Stress-aged Mild Steel

Effect of the Stress-aging Treatment on Strain-aging Behaviour of Mild Steel

Strain Aging of Mild Steel under Tensile Stress