High Dislocation Research Articles

Temperature induced strengthening in TiNiCuNb shape memory alloy

Mechanical behavior of two-phase (Ti54Ni34Cu12)90Nb10 alloy with B2–B19–B19’ martensitic transformation types was studied by tensile test in wide temperature range. A temperature-dependent stress diagram was obtained based on experimental data, from which the influence of temperature on the different critical stresses was determined. It was shown that the increasing in testing temperature leads to the increasing in dislocation yield of martensite and ultimate fracture stresses, while the dislocation yielding stresses of austenite are stabilized. It was proposed that the phase hardening caused by difference in thermal expansion coefficients between B19 and β-Nb phases may be a possible reason for the temperature induced strengthening. High dislocation density near B19/β-Nb interface supports this assumption.

Effects of cutting conditions on materials properties of austenitic stainless steels

Austenitic stainless steel SUS304 is widely used in various engineering applications, including semiconductor manufacturing equipment and food processing machinery, owing to its exceptional material characteristics such as non-magnetic properties, high corrosion resistance, strength, and ductility. However, concerns have arisen in recent years regarding potential alterations in the material properties of austenitic stainless steel after machining processes. As the cutting process was conducted widely to make various engineering applications with different machining conditions, an examination of the effect of machining conditions on the material properties is important. In the present study, the influence of cutting conditions on the microstructure and mechanical of SUS304 was experimentally and numerically investigated, where three types of ball-end mills with rake angles (- 20°, − 3°, and 5°) and different cutting speeds (50 m･min−1 and 100 m･min−1) were conducted with plane and side machining to investigate the cutting properties. Material properties of SUS304 can be changed by the cutting resistance of the above cutting process, in particular the low rake angles under plane machining, where the high cutting resistance makes high dislocation density and strain-induced martensite formation. This occurrence made the low corrosion resistance as well as low ductility. On the contrary, no significant effect of the cutting speeds on the cutting resistance was detected compared to the condition of the rake angle on the plane machining. The reasons behind this will be discussed in detail systematically in this paper. From this approach, it could be clarified to maintain the high material properties of SUS304 even after the cutting process, which could be useful to make design of the engineering applications.

Crystal Plasticity Modeling to Capture Microstructural Variations in Cold-Sprayed Materials

The high-velocity impact of powder particles in cold-spray additively manufactured (CSAM) parts creates intersplat boundaries with regions of high dislocation densities and sub-grain structures. Upon microstructure and mechanical characterization, CSAM Aluminum 6061 showed non-uniformity with spatial variation in the microstructure and mechanical properties, affecting the overall response of the additively manufactured parts. Post-processing treatments are conducted in as-printed samples to improve particle bonding, relieve residual stresses, and improve mechanical properties. In this work, we attempt to implement the effects of grain size and distribution of smaller grains along the intersplat boundaries using the grain size distribution function and powder size information to accurately predict the deformation response of cold-sprayed material using a mean-field viscoplastic self-consistent (VPSC) model. The incorporation of an intersplat boundary term in the VPSC model resulted in a stress–strain response closely matching the experimental findings, preventing the superficially high stresses observed due to Hall–Petch effects from ultra-fine-grain structures. Likewise, the results from the grain analysis showed the combined effects of grain size, orientation, and intersplat mechanisms that captured the stresses experienced and strain accommodated by individual grains.

해양구조물용 YS 420MPa 강재 Flux Cored Arc 용접금속의 기계적 성질에 미치는 용접 자세의 영향

This study investigated the mechanical properties of flux-cored arc weld metal of 420-MPa yield-strength (YS) steels for offshore structures based on welding position. Results showed that the recovery rate of alloying elements in the horizontal-position weld metal was higher than that in the vertical-up-position weld metal, and the fraction of low-temperature transformation phases with high dislocation density in the horizontal-position weld metal was high. Consequently, the YS, tensile strength, and impact toughness of the horizontal-position weld metal were higher than those of the vertical-up-position weld metal. In addition, the impact toughness of the weld metal was affected to a greater extent by the microstructure and fraction of the weld metal itself than by the fraction of the martensite-austenite constituents.

Résultats à long terme de l’arthroplastie totale dans les luxations congénitales de la hanche. Étude rétrospective des résultats avec 10 à 20 ans de recul

Introduction: The impact of bone deformities, previous surgeries, and the surgical technique in total hip arthroplasty (THA) for congenital dislocation of the hip (CDH) at a long-term has not been clearly defined yet. In this single-centre observational study we sought to assess patients undergoing THA due to osteoarthritis secondary to severe CDH with low or high dislocation ten- to 20-years after surgery. To determine this purpose, we assessed: 1) THA-related complications and reoperations; 2) the clinical outcome, patients´ satisfaction and radiological results; and 3) the possible risk factors for reoperation with particular attention to the surgical technique and the influence of prior surgeries.Hypothesis: We hypothesized that an anatomical reconstruction of the hip would decrease the reoperations rates in patients undergoing THA with severe CDH.Methods: Seventy-five patients (85 hips) operated between 1999 and 2012 at our large tertiary hospital were analyzed. Fifty-six hips were diagnosed as low dislocation (group 1) and 29 hips as high dislocation (group 2). The existence of prior surgeries was frequent: group 1, pelvic osteotomies 6 hips, femoral osteotomies 7, tectoplasty (shelf) 6, resection arthroplasty 1 and lowering of the greater trochanter 1; group 2 included pelvic osteotomies 10 hips, femoral osteotomies 10, and a femoral lengthening 2. The number of additional procedures during THA was: group 1 (19/56 (34%)), acetabular roof bone autograft 8 hips, acetabular medial wall autograft 2, hardware removal 6, extended femoral osteotomy 2, and a femoral shortening 1; group 2 (20/29 (69%)), acetabular bone autograft 12 hips, medial autograft 1, hardware removal 1, extended femoral osteotomy 2, and a femoral shortening 4 hips The clinical and the radiological analysis were compared in both groups for a minimum follow-up of ten years. Cox regression models were used to detect risk factors for reoperation.Results: Nine patients (13.8%) required reoperation for the following reasons: cup loosening (5 hips), periprosthetic femoral fracture (3) and stem loosening (1); seven had prior surgeries. The 12-year survival rate for reoperation for any reason was 96.3% (95% Confidence Interval (CI) 91.2-100) in group 1 and 75.7% (95% CI, 65.8-90.8) in group 2 (p=0.003). Patients with high dislocation (p=0.02, Hazard Ratio (HR): 6.25, 95% CI, 1.26-30.9) and those with an acetabular component inclination placed out of the target zone between 35º and 50º (p=0.03, HR: 4,27, 95% CI, 1.13-16.1) had a higher risk of reoperation.Discussion: An optimal placement of the acetabular component decreased the reoperation rates in patients undergoing THA for severe CDH. Hips with high dislocation and the existence of prior surgery can affect THA implantation.Level of Evidence: III; retrospective; comparative

The Creep‐Induced Micro‐ and Nanostructural Evolution of a Eutectic Mo–Si–Ti Alloy at 1200 °C

In the present study, the creep deformation mechanisms of a eutectic Mo–Si–Ti alloy (comprising a body‐centered solid solution and a hexagonal silicide) are verified. The microstructural changes occurring at the various microstructural length scales are correlated to the nature of the creep curve. The creep curve exhibits a transient strain‐hardening region followed by a distinct minimum and then creep rate accelerates after that. The formation of a high fraction of disperse (Ti,Mo)5Si3 precipitates in the solid solution lead to significant strengthening in the transient creep regime. By the simultaneous decrease of the initially high dislocation density in the solid solution, diffusional creep contributes to effective creep behavior. At the minimum, the load and strain are also carried by the silicide phase which undergoes plastic deformation. Continuous coarsening of precipitates and loss of precipitation strengthening in the solid solution and dynamic recovery in the silicide phase lead to creep acceleration.

Insights into the deformation mechanisms of an Al1Mg0.4Si alloy at cryogenic temperature: An integration of experiments and crystal plasticity modeling

In this work, we investigated the mechanical properties and corresponding deformation mechanisms of an Al1Mg0.4Si alloy, which exhibited significantly higher strength and outstanding strain hardening capacity at 77 K compared to its counterparts at 298 K. The deformation mechanisms responsible for the excellent strength-ductility synergy and extraordinary strain hardening capacity at cryogenic temperature were elucidated through a combined experimental and simulation study. The results reveal the presence of numerous slip traces and microbands throughout grain surfaces during deformation at 298 K, whereas at 77 K, vague grain surfaces dominate, indicating the simultaneous operation of multiple slip systems. Transmission electron microscopy (TEM) analysis using the two-beam diffraction technique demonstrates the presence of dislocations with several different Burgers vectors inside a grain at cryogenic temperature, confirming the activation of multiple slip systems. The accumulation of dislocations facilitated by these multiple slip systems, combined with the high dislocation density, contributes to strain hardening and remarkable uniform elongation at 77 K. A modified dislocation density-based crystal plasticity model, incorporating the effect of grain boundary hardening (GBH) and temperature, was developed to gain a better understanding of the underlying mechanisms governing alloy's strength and plasticity. The GBH effect significantly enhances statistically stored dislocation (SSD) density and screw dislocation proportion, which promote homogeneous deformation and enhance strain hardening capacity at cryogenic temperature. These findings deepen the understanding of plastic deformation at cryogenic temperatures and pave the way for the development of ultrahigh-performance metallic materials for cryogenic applications.

Quench sensitivity of the extruded Mg-6Zn-0.2Zr/Mg2Si composite: Position dependence and role of dislocation density

The quench sensitivity of the Mg-6Zn-0.2Zr/Mg2Si composite is investigated by microstructure and mechanical properties analysis. It is position-dependent, which is high in the center and low on the surface of the composite. In the center, the mismatch in the CTE between the Mg2Si and Mg matrix leads to high dislocation density in the matrix upon fast quenching, which promotes age hardening. The dislocation density decreases for a lower quenching rate, and leads to lower hardness. Such origin of quench sensitivity is specific to the magnesium composite in addition to the well-recognized solute and vacancy loss. On the surface, low concentration of Zn element leads to low hardness under both cooling conditions. The dislocation and precipitates act as a buffer zone to mitigate the strain incompatibility, which alleviate stress concentration near the Mg/Mg2Si interface. So, the interface debonding is delayed, and twin growth is suppressed. The lower quenching rate negates such a beneficial effect.

The abnormal carbon redistribution in lath martensite during tempering in Mn-patterned steels

Martensite tempering is a critical step to achieve high strength with decent ductility. It is well-known that, during tempering, the carbon is sequentially arranged as segregation, transition carbide and cementite. Abnormally, this study shows the absence of carbide precipitation in Mn-depleted martensite during tempering when Mn distribution is heterogeneous between austenite and martensite. After fast heating and short austenitization from Mn-depleted ferrite and Mn-enriched cementite, the high-temperature austenite with Mn heterogeneous distribution has formed, resulting in the formation of alternating Mn-depleted lath martensite and Mn-enriched film retained austenite (RA) after quenching. In comparison with the carbide precipitation in conventional lath martensite with Mn homogeneous distribution during tempering at 150–500°C, carbide formation is completely inhibited in Mn-depleted lath martensite. Instead, carbon atoms diffuse from Mn-depleted martensite to its neighboring Mn-enriched film RA, leading to an increased carbon content in RA. This is mainly attributed to the strong interaction between Mn and carbon, further assisted by high dislocation density and small width of lath martensite. Additionally, this RA can promote carbon diffusion in the interior due to its gradient Mn distribution.

Superior strength and ductility in a C-containing CoCrFeNiMn high-entropy alloy with heterogeneous microstructure

The present study is focused on the beneficial effects of adding few amounts of carbon (0.76 at. %) and adopting microstructure engineering by a simple thermomechanical treatment to form a heterogeneous microstructure in a CoCrFeNiMn high-entropy alloy. The results demonstrate that the addition of carbon results in significantly higher strength and improved thermal stability when compared to carbon-free alloy under identical conditions. In fact, the addition of carbon results in strengthening through the solute drag effect and solid solution strengthening. Thermodynamic predictions and XRD patterns indicate that carbon addition enhances the tendency of carbide precipitation in the alloy instead of forming an undesirable σ phase. The microstructural observation reveals that the deformed microstructure remains nearly stable during annealing at temperatures up to 750 °C and complete recrystallization occurs after annealing at 1000 °C, resulting in the formation of a fine-grained microstructure. Post-deformation annealing at 800 and 900 °C leads to the formation of heterogeneous microstructures comprising regions with high dislocation density grains alongside recrystallized fine-grained areas. The results suggest a superior synergy between strength and ductility in the annealed sample at 800 and 900 °C, exhibiting the ultimate-tensile strength of ∼1000 and ∼835 MPa. Additionally, these samples demonstrate decent uniform elongation values of ∼10 and 20%, respectively.

Effect of microstructure on the corrosion-friction behavior of low-carbon martensitic stainless steel

The effect of microstructure on the corrosion-friction behavior of 11Cr4NiMo steel was investigated for three different microstructure states. Quenched martensite and low-temperature tempered martensite with high density dislocations exhibit severe wear under the dual effects of corrosion and abrasion, and their wear mechanism include three-body wear, adhesive wear, and fatigue wear. While high-temperature tempered microstructure mixed structure of tempered martensite, reversed austenite, and M23C6 carbides exhibits weakened wear. Reversed austenite greatly promotes the generation of a dense and stable passivation film with corrosion product of α-FeOOH, and plays a lubricating role and attenuates three-body wear. Utilizing the passivation film induced by corrosion to improve the wear resistance of materials is of great significance in engineering applications.

Tailoring deformation-induced martensitic transformation through cellular engineering in laser powder bed fusion processed 316L stainless steel

The microstructural effect of 316L stainless steel (SS) fabricated by laser powder bed fusion on deformation-induced martensitic transformation (DIMT) was investigated. Both opposing effects, i.e., disturbing/promoting DIMT were observed. While the cellular structure and low-angle grain boundaries reduce the DIMT rate by disturbing shear band formation, the high dislocation density can activate direct BCC martensite nucleation and accelerate the DIMT. This observation suggests that controlling the two competing effects is the key to cellular engineering using additive manufacturing.

Comparison of Clinical Outcomes Among Sutured, Sutureless Scleral Fixation, and Retropupillary Fixation of Intraocular Lens

Purpose: To compare the short-term clinical outcomes (up to 3 months) after three different secondary intraocular lens (IOL) implantations in dislocated and aphakic eyes with insufficient capsular support.Methods: We retrospectively analyzed the medical records of 97 patients who underwent secondary IOL implantation (32 eyes with sutured scleral fixation, 21 with sutureless scleral fixation, and 44 with retropupillary IOL implantation) from March to December 2018. Uncorrected visual acuity (UCVA), and best-corrected visual acuity (BCVA), spherical equivalent (SE), prediction error (PE), mean absolute error (MAE), surgically induced astigmatism (SIA), ocular residual astigmatism (ORA), and complications in the three groups were assessed before and 1 week and 1 and 3 months after surgery.Results: All groups had an improved BCVA beginning 1 month after surgery. The pre- and postoperative SE (<i>p</i> = 0.857, <i>p</i> = 0.263, and <i>p</i> = 0.163) and PE (<i>p</i> = 0.479, <i>p</i> = 0.848, and <i>p</i> = 0.128) did not differ in the sutured scleral fixation, sutureless scleral fixation, and retropupillary IOL implantation groups, respectively; MAE differed significantly among the procedures 1 week after surgery (1.33 ± 1.25, 1.40 ± 1.54, and 0.85 ± 1.25, <i>p</i> = 0.044), but not 1 month after surgery (<i>p</i> = 0.965, <i>p</i> = 0.731). 3 months after surgery, there was no significant difference in SIA (<i>p</i> = 0.140) or ORA (<i>p</i> = 0.178) among the 3 groups. As a complication, intraocular pressure rise occurred more often in the sutured fixated group, while the retropupillary group had a higher dislocation rate.Conclusions: There was no significant difference in the SE, PE, MAE, SIA, ORA, or complications among the three procedures. Surgical skill is still required to minimize the chance of complications regardless of the implantation method.

Взаимосвязь микроструктуры с ударной вязкостью металлов сварного шва трубных высокопрочных низколегированных сталей (обзор исследований)

Introduction. The modern pipeline industry requires the development of materials of high strength and toughness for the production of steels for oil and gas pipelines. Changes in steel production and rolling technologies have become a challenge for welding consumables and joining technologies. This is more critical for strength levels above 830 MPa, where there are no specific regulations for the approval of welding consumables. Research methods. The failure of stainless steel pipeline welds is becoming a serious problem in the pipeline industry. Multiphase microstructures containing acicular ferrite or an acicular ferrite-dominated phase exhibit good complex properties in HSLA steels. This paper focuses on the results obtained using modern methods of scanning electron microscopy for microstructural analysis, backscattered electrons (BSE) for electron channel contrast imaging (ECCI) and orientation microscopy based on electron backscatter diffraction (ORM), as well as characteristic X-rays for compositional analysis using energy-dispersive X-ray spectroscopy (XEDS) and secondary electrons (SE) for observing surface morphology. Results and discussion. This paper analyzes the characteristics of the microstructure of the weld and its relationship with impact toughness. It is shown that predicting impact toughness based on the microstructural characteristics of steel weld metals is complicated due to the large number of parameters involved. This requires an optimal microstructure of the steel. Satisfactory microstructure depends on several factors, such as chemical composition, hot work processing, and accelerated cooling. Alloying elements have a complex effect on the properties of steel, and alloying additives commonly added to the steel composition include Mn, Mo, Ti, Nb and V. From a metallurgical point of view, the choice of alloying elements and the metallurgical process can greatly influence the resulting microstructure. A longer cooling time tend to improve the toughness and reduce the mechanical strength of weld deposits on high-strength steels. Welding thermal cycles cause significant changes in the mechanical properties of the base material. The analysis showed that impact toughness strongly depends on the microstructure of the multi-pass weld of the material under study, which contains several sources of heterogeneity, such as interdendritic segregation, and the effective grain size can also be a significant factor explaining large deviations in local impact toughness values. Acicular ferrite nucleated in intragranular inclusions has been shown to produce a fine-grained interlocking arrangement of ferrite plates providing high tensile strength and excellent toughness, and is therefore a desirable microstructural constituent in C-Mn steel weld metals. At the same time, discussion regarding the relationship between acicular ferrite and toughness is very complex and still open at present. Relating impact toughness to acicular ferrite, taking into account the top bead, is not a reliable procedure, even for single-pass deposit welding. Impact strength depends on several factors, and the strong effect of acicular ferrite is generally recognized due to its fine-grained interlocking structure, which prevents the propagation of brittle cracks by cleavage. The large-angle boundaries and high dislocation density of acicular ferrite provide high strength and toughness. However, for the same amount of acicular ferrite, different viscosity values may be observed depending on the content of microalloying elements in the steel. An analysis of the results of various studies showed that other factors also affect the impact strength. For example, microphases present along the Charpy-V notch are critical for the toughness of weld metals. The combination of OM, SEM and EBSD techniques provides an interesting method for metallographic investigation of the refined metal microstructure of stainless steel pipeline welds. Conclusion. This review reports the most representative study regarding the microstructural factor in the weld of pipe steels. It includes a summary of the most important process variables, material properties, regulatory guidelines, and microstructure characteristics and mechanical properties of the joints. This review is intended to benefit readers from a variety of backgrounds, from non-welding or materials scientists to various industrial application specialists and researchers.

The mechanism for annealing-induced ductile to brittle transition in a high-temperature titanium alloy and its mitigation

By investigating the relation between microstructure evolution and tensile responses of a BTi6431S alloy at room temperature and 700 °C, this study finds an annealing-induced ductile-to-brittle transition phenomenon in the near-α titanium alloy. The high strength of the as-received BTi6431S alloy is rooted in the high dislocation density and collective dislocation behavior in the α phase. However, after annealing at 650 °C, the alloy exhibits brittle fracture at room temperature. Using multiscale characterization methods, we attribute this phenomenon to the presence of brittle precipitates and the change of dislocation structures near the surface of BTi6431S titanium alloy. Silicides are generated in the vicinity of the surface region due to the relatively high dislocation density on the surface after the rolling process. The room temperature ductility can be restored by removing the near-surface area. When the alloy is tested at 700 °C, most of the near-surface brittle silicides and dislocations can be eliminated, because the deformation is mainly affected by dislocation behavior and dynamic recrystallization at high temperature. The findings in this study can advance the understanding of alloying effects on the mechanical behavior of high-temperature titanium alloy. The results suggest that inhibiting silicide formation and controlling the environmental temperature during service are potential approaches for maintaining the mechanical performance of this near-α titanium alloy.

Tailoring short-range order and dislocation evolution in Cr–Co–Ni medium-entropy alloys: A molecular dynamics study

The research community has recently been captivated by the atomic-scale short-range order observed in high- and medium-entropy alloys. However, significant challenges persist in improving the mechanical performance through manipulation of the short-range order. Herein, molecular dynamics simulations are employed to establish the correlation between this ordering and the chemical composition for the Cr–Co–Ni medium-entropy alloys. It is demonstrated that atomic-scale clustering can be tailored through adjusting the chemical composition. Particularly, it can be promoted by decreasing the content of elements that do not participate in the clusters. The short-range ordering plays a significant role in affecting the dislocation evolution and tensile properties. Reducing the tendency to form Cr–Co clusters yields enhanced strengthening due to the increased local unstable stacking fault energy. Increasing the tendency to form Ni–Ni clusters instead results in enhanced strain hardening due to the high sessile dislocation density impeding the movement of dislocations. These findings unveil the crucial role of chemical composition on short-range ordering and have significant implications on the design of high-performance high- and medium-entropy alloys.

Crack nucleation and dislocation activities in titanium alloys with the strong transverse texture: Insights for enhancing dwell fatigue resistance

Cold dwell sensitivity of near α titanium alloys has posed a significant challenge to the engineering safety within the aerospace industry. However, there exists inconsistency regarding the critical facet formation mechanism between basal and prismatic nucleation. A key revelation in this paper is that the controversy surrounding the facet nucleation plane primarily arises from variations in texture: when the loading direction is parallel to the c-axis or at a 45 ° angle, it leads to basal plane cracking, whereas loading direction perpendicular to the c-axis results in prismatic plane cracking. What's more, a large anisotropy is observed in the dwell fatigue performance in descending order: rolling direction (RD) > transverse direction (TD) >45° direction. To be specific, the dwell fatigue life of RD specimens was 2 times and 4.07 times longer than that of TD and 45 ° specimens, which exhibits excellent dwell fatigue resistance. Furthermore, the high prismatic dislocation density near the facet of RD specimen was confirmed through the Transmission Electron Microscope (TEM) and Transmission Kikuchi Diffraction (TKD) map, which is evidenced that prismatic slips lead to higher strain hardening during cyclic loading. The basal plane of facet grain is generally parallel to the facet line, indicating that the elliptical facet developed by the transgranular fracture through basal plane. Twinning activation in hard grain to accommodate deformation in Ti60 alloy is firstly observed under dwell fatigue tests, which is a product of high stress level in the hard grain. This paper unveils the significant impact of texture on dwell fatigue resistance, offering novel insights into enhancing dwell fatigue performance through texture control.

Treatment of bilateral developmental dysplasia of the hip joint with an improved technique: A case report

BACKGROUND Developmental dysplasia of the hip (DDH) is a common osteoarticular deformity in pediatric orthopedics. A patient with bilateral DDH was diagnosed and treated using our improved technique "(powerful overturning acetabuloplasty)" combined with femoral rotational shortening osteotomy. CASE SUMMARY A 4-year-old girl who was diagnosed with bilateral DDH could not stand normally, and sought surgical treatment to solve the problem of double hip extension and standing. As this child had high dislocation of the hip joint and the acetabular index was high, we changed the traditional acetabuloplasty to "powerful turnover acetabuloplasty" combined with femoral rotation shortening osteotomy. During the short-term postoperative follow-up (1, 3, 6, 9, 12, and 15 months), the child had no discomfort in her lower limbs. After the braces and internal fixation plates were removed, formal rehabilitation training was actively carried out. CONCLUSION Our "powerful overturning acetabuloplasty" combined with femoral rotational shortening osteotomy is feasible in the treatment of DDH in children. This technology may be widely used in the clinic.

Multi-microscopy characterization of threading dislocations in CVD-grown diamond films

We present site-coincident imaging of a high dislocation density boron-doped chemical vapor deposition-grown homoepitaxial (001) diamond film using electron channeling contrast imaging (ECCI), cathodoluminescence, transmission electron microscopy (TEM), and scanning secondary ion mass spectroscopy (SIMS). With growing interest in large area heteroepitaxial substrates, we show that ECCI is a promising technique to accurately evaluate dislocations in diamond films. We find the electron backscatter yield is sufficient to distinguish individual threading dislocations in ECCI despite the low atomic number of carbon, and we have generally good agreement between dislocations observed in ECCI and TEM of the same region. Importantly, relying on luminescence in the 430 nm dislocation-related A-band alone results in an underestimation of the defect density as we find only 20%–40% of the threading dislocations luminesce. We further show that dislocations do not perturb the spatial uniformity of boron doping measured by SIMS, even when the dislocations are clustered with high density, and we can tentatively rule out strong segregation effects at the dislocations. Our results establish the complementary use of microscopy and microanalysis methods to rapidly characterize and understand the impact of dislocations in diamond thin films.

Elucidating the dual effect of vanadium microalloying on hot deformation behavior of high nitrogen martensitic stainless steel

Precipitates always have a complex effect on the hot work hardening and recrystallization softening of materials. In this work, the dual effect of V-microalloying on hot deformation behavior and microstructure evolution of high nitrogen martensitic stainless steel (HNMSS) was investigated by hot compression experiments, modeling study and microstructure characterization. The results showed that V-microalloying enhanced the flow stresses and activation energy of 0.2V steel due to the fine grain strengthening effect and the blocking effect of dynamic precipitation on dislocation movement and grain boundary migration. On the other hand, the recrystallization model and deformed microstructure indicated the more intense dynamic recrystallization (DRX) softening effect in 0.2V steel, inducing the faster decrease of flow stress after the peak stress. V-microalloying promoted the dynamic precipitation of HNMSS during hot deformation, which reduced the size and increased the number of precipitates in 0.2V steel. The fine precipitates hindered dislocation movement, promoted dislocation accumulation and entanglement, formed a particle deformation zone (PDZ) with high dislocation density and large orientation gradient, and then induced the occurrence of particle-stimulated nucleation (PSN). In addition, the dislocation cells evolved from dislocation entanglement were also favorable nucleation sites for DRX.