Slip Band Spacing Research Articles

Ｍｎ系分散物を含むＡｌ‐１％Ｍｇ２Ｓｉ‐０．４％Ｓｉ合金の延性に及ぼす結晶粒度の影響

The effects of grain size and Mn on ductility of Al-1%Mg2Si-0.4%Si base alloys were examined by tensile test.When grain size was large as 600μm, elongation was slightly increased with increase of Mn at peak aged (200°C) condition of the alloys containing upto 0.5%Mn. While, if grain size was so small as about 50μm, elongation was almost independent of Mn in the alloys containing 0.20.8%Mn.Although grain size varied from 50 to 600μm, intergranular fracture surface was always observed at peak aged (150 and 200°C) condition of 0.5%Mn addition alloys, which had the Mn bearing dispersoids of a mean diameter of 0.2μm.The slip band spacing was decreased with decrease of grain size in 0.5%Mn addition alloys.

Fatigue crack growth and fracture toughness behavior of an Al-Li-Cu alloy

Slip behavior, fracture toughness, and fatigue thresholds of a high purity Al-Li-Cu alloy with Zr as a dispersoid forming element have been studied as a function of aging time. The fracture toughness variation with aging time has been related to the changes in slip planarity,i.e., slip band spacing and width. Although the current alloy exhibits planar slip for all aging conditions examined, the crack initiation toughness,Klc, compares favorably with those of 2XXX and 7XXX aluminum alloys. Near threshold fatigue crack growth results in air and vacuum suggest that irregularities in the crack profile and the fracture surfaces and slip reversibility are some of the major contributing factors to the crack growth resistance of this alloy.

Ａｌ‐１％Ｍｇ２Ｓｉ‐０．４％Ｓｉ合金の延性に及ぼすＭｎ添加の影響

The Effect of Mn on ductility of Al-1%Mg2Si-0.4%Si alloy was investigated by tensile test and optical and transmission electron microscopies observation. When the peak aged alloy is free from Mn bearing dispersoids, elongation increases up to about 9% with decrease of grain size. If the aging temperature is constant, the width of precipitale free zones was almost independent of grain size in 0.2%Mn addition alloys. While the spacing of slip bands of specimen surface extends with increase of grain size. These dependence of slip band spacing on grain is more distinct, when the intergranular fracture is a dominant factor governing the fracture.

The Effect of Solute Content on the Slip Behavior in 7XXX Series Aluminum Alloys

The microstructures of three high strength, high purity Al-Zn-Mg-Cu alloys, in the T6 temper, were characterized extensively using quantitative optical metallography and quantitative transmission electron microscopy. Only the solute content (Mg + Zn) of these alloys was varied for this study. These alloys were shown to be identical in grain size and shape, dispersoid (E-phase) and grain boundary precipitate (ν) populations, and precipitate free zone widths. The matrix microstructures consisted of ordered GP zones and ν′ and differed only in the volume fraction of these strengthening precipitates. The higher solute alloys had the higher yield strengths and volume fractions of matrix precipitates. Subsequent slip behavior analysis of prestrained tensile specimens demonstrated that slip band spacings and slip step heights increased with increasing solute content for the same macroscopic strain (ep = 0.02). A work softening model by Hornbogen and Gahr was shown to predict this tendency toward increased strain localization with higher solute levels.

A comment on “a comparison of the dimple spacing on intergranular creep fracture surfaces with the slip band spacing for copper”

A comment on “a comparison of the dimple spacing on intergranular creep fracture surfaces with the slip band spacing for copper”

A comparison of the dimple spacing on intergranular creep fracture surfaces with the slip band spacing for copper

We have shown that the dimple spacing on intergranular creep fracture surfaces of copper coincides with the slip band spacing and that both quantities are inversely proportional to the applied stress. This correlation between slip band formation and cavity nucleation suggests that cavities may be nucleated by a process involving the intersection of slip bands and grain boundaries.

The influence of MN additions on the deformation behaviour of an AlMgSi alloy

The deformation behaviour at low plastic strains of three AlMgSi alloys in the fully aged condition has been studied. The MN-free alloy (BD3) plastically deforms to form narrow slip bands whose spacing decreases slightly with increasing strain. This alloy fails intergranularly at low strain because the high stress concentrations at the head of the slip bands nucleate voids at grain boundary precipitates which then propagate by coalescence within the PFZ. The two Mn-bearing alloys (BD3 and BDS) contain volume fractions of 0.004 and 0.011 respectively of 0.1 μm dia. incoherent particles of α-Al 12Mn 3Si. as well as the age-hardening phase. At small strains these alloys develop slip bands of slightly smaller spacing than those in BD3. out with increasing strain the slip band spacing decreases until at 9% strain are no longer resolvable in BD8. The Mn-phase thus causes lateral spreading of the slip bands, giving rise to significantly smaller stress concentrations at the head of the slip bands, and whose magnitude is further reduced by the smaller grain size of these alloys. A semi-quantitative assessment of these two contributions to the local grain boundary stress has been made. It is concluded that intergranular failure in BD6 and BD8 is suppressed at low strains because the associated stress concentrations are insufficient to produce decohesion at the grain boundary precipitates.

Polycrystalline strengthening

Slip band formation in a β-titanium Ti-9.8 wt. % Mn alloy was found to start at grain boundaries and proceed inward. Volume fraction of grain boundary deformation, V gb , average grain boundary slip band spacing /- S gb , average interior spacing, /- S( Inb) and overall average slip band spacing S AV were measured. By referring 1 S ̄ gb and 1/ S ̄ (Inb) to curves of applied stress, σ T, vs 1 S AV it was possible to obtain values of average grain boundary stress, \\ ̄ gs gb and interior stress σ B and to calculate the applied stress with reasonable accuracy from \\ ̄ gs gb , \\ ̄ gs B and V gb · \\ ̄ gs gb was found to be larger than \\ ̄ gs B at small strains. Although both \\ ̄ gs gb and \\ ̄ gs B increased with strain, \\ ̄ gs B increased more rapidly, becoming essentially the same as \\ ̄ gs gb at 2 per cent strain. Based on experimental observations an expression for polycrystalline strengthening at constant strain as a function of grain size has been derived.

Irradiation hardening and annealing in copper at high neutron fluences

Abstract Irradiation hardening has been investigated in copper crystals irradiated at ∼325 K with 4 × 1020 and 8 × 1020 n cm−2. In the as-irradiated crystals, cleared channels were produced due to the sweeping up of the irradiation damage by the glide dislocations. The slip band width, spacing and height all increased with increasing testing temperature. Identical post-irradiation annealing treatments produced a larger fractional recovery of the critical resolved shear stress at 4 K than at 295 K. This indicates that the damage removed in the early stages of annealing acts as a more effective obstacle to dislocation glide at 4 K than at 295 K. For certain combinations of annealing treatment and low temperature testing, the initial stage of deformation was characterized by the bowing of the glide dislocations around the defects rather than sweeping them up. In polycrystalline copper, migrating grain and twin boundaries were quite effective in sweeping out the irradiation-produced defects.

Mechanical behavior of chemical

Hoop stress and tensile tests have been completed between 800° and 1600°C on chemical vapor deposited (C.V.D.) tungsten specimens. Scanning electron microscopy of slip surfaces showed a fairly constant value of slip band spacing of between 2 and 20 μ. Fracture face morphologies suggest a transition from brittle failure at 800cC to ductile fibrous failure at 1400°C. Slip band intersections are almost exclusively at 90 deg indicating 110 slip planes with <100= zone axes. The latter fact confirms earlier <100< fiber axis results from X-ray diffraction. Ductility first increased from 800° to 1400°C, above which it decreased.

Creep behavior of molybdenum single crystals

The creep behavior of molybdenum single crystals oriented with a [011] direction parallel to the tensile axis was investigated over the temperature range 1200° to 1917°C (0.5 to 0.76 T m). The activation energy for creep at applied stresses of 900 psi and 2050 psi was 108 and 105 kcal/mol, respectively. No steady state creep was observed, although the creep rate was approaching a constant value at 0.45 creep strain. The transient creep strain was fitted to a relation ϵ = ϵ 0 + bt m , yielding b ∝ σ 3.8 at 1410°C, and 0.37 < m < 0.71, with m increasing with increasing temperature. The analysis of slip bands and Laue back reflection patterns indicated that {112}〈111〉 was the primary slip mode for [011] crystals crept at these temperatures. The slip distribution was very non-uniform, being concentrated into regularly spaced, narrow bands. The slip band spacing decreased with increasing stress.

Slip in Single Crystals of Ice

AbstractRectangular specimens of ice (c. 5 cm × 2 cm × 0.5 cm) were cut from large single crystals (c, 10 cm × 5 cm2) grown from pure water by a modified Bridgman technique. When these specimens were deformed under controlled conditions, slip lines which were predominantly parallel to the basal plane became visible. In some cases short. perpendicular segments were also seen which can be interpreted as evidence for cross-slip in ice. Measurements of slip-band spacings were made on silvered “formvar” replicas of some deformed crystals. These measurements showed that “coarse” slip occurred when the resolved shear stress on the basal plane. σ, was greater than about 0.2 bars, and that the average thickness of the slip lamellae, d (cm) was approximately given by Wakahama’s relationship. (σ−0.2) d = 0.45 × 10−3. At lower stresses “fine” slip occurred, and the relationship between the average thickness of the lamellae and the resolved shear stress was more adequately described by Taylor’s formula, σd = 7.2 × 10−5. It is. however, possible that both coarse and fine slip occurred at higher stresses, but that the fine slip was then below the limit of resolution.

Slip in Single Crystals of Ice

AbstractRectangular specimens of ice (c.5 cm × 2 cm × 0.5 cm) were cut from large single crystals (c, 10 cm × 5 cm2) grown from pure water by a modified Bridgman technique. When these specimens were deformed under controlled conditions, slip lines which were predominantly parallel to the basal plane became visible. In some cases short. perpendicular segments were also seen which can be interpreted as evidence for cross-slip in ice. Measurements of slip-band spacings were made on silvered “formvar” replicas of some deformed crystals. These measurements showed that “coarse” slip occurred when the resolved shear stress on the basal plane.σ, was greater than about 0.2 bars, and that the average thickness of the slip lamellae,d(cm) was approximately given by Wakahama’s relationship. (σ−0.2)d= 0.45 × 10−3. At lower stresses “fine” slip occurred, and the relationship between the average thickness of the lamellae and the resolved shear stress was more adequately described by Taylor’s formula,σd= 7.2 × 10−5. It is. however, possible that both coarse and fine slip occurred at higher stresses, but that the fine slip was then below the limit of resolution.

Some Observations of Subgrain Formation During Creep in High Purity Aluminum

Coarse grained high purity aluminum was tested in creep at temperatures of 400° to 1200°F to develop subgrain structures. Measurements of subgrain size, distribution, and rotation were made from X-ray diffraction patterns. Subgrain size and distribution were checked metallographically and the size was compared with average slip band spacing. The slip family was determined for several specimens.

Origin and Spacing of Slip Bands

SLIP bands on plastically deformed crystals are very much more equidistant than would correspond to statistical disorder; except in the first stage of deformation, their spacing fluctuates around a mean value which is usually between 0.5 μ and 10 μ. This remarkable phenomenon seems to have a simple explanation. Consider a crystal lattice subjected to a shear stress σ which produces the elastic strain s = tan α = σ /G (G is modulus of shear). Suppose that slip takes place in the slip plane p-p (see accompanying diagram) over an area the linear dimensions of which are great compared with the atomic distance, but small compared with the size of the crystal. The slipped area is surrounded by a dislocation zone D,D, and the stress in its immediate neighbourhood has fallen to a small amount which we assume to be zero. The question is, how far the zone of greatly diminished stress stretches on the two sides of the slip plane.