Stress Annealing Research Articles

Co-optimizing of H-curing, stress, and thermal annealing—A more effective way for realizing FEOL-BEOL compatible eMRAM chip

Metallization, plasma, and thermal annealing used in magneto-resistive random access memory integration differs significantly from traditional interconnection processes, usually resulting in the device performance deterioration of metal-oxide-silicon field-effect transistors. Commonly used methods, such as hydrogen postalloying, may not be effective to recover performance when magneto-resistive random access memory is integrated. The study focused on the interplay between hydrogen content in the dielectric films, wafer configuration induced by film stress, and thermal annealing during the chip fabrication process. Post-thermal annealing can enhance the release of hydrogen from the dielectric films, which can repair the silicon–hydrogen bond breakage resulting from magneto-resistive random access memory integration. However, this process can also worsen wafer bowing in an undesired direction which is detrimental to the performance of metal-oxide-silicon field-effect transistors. Consequently, utilizing silicon nitride with specific hydrogen content, in conjunction with post-thermal annealing, can improve effectively both p-type and n-type metal-oxide-silicon field-effect transistors. This approach holds significant potential for application in more advanced technological nodes since it is compatible with traditional process and does not require more advanced fabrication equipment. Additionally, the resulting embedded magneto-resistive random access memory chips maintain competitive magnetic tunneling junction reliability in term of endurance and reflow resistivity.

A two-step stress-annealing with stress-relaxation process for developing low-loss Fe-based nanocrystalline soft magnetic cores

Fe72.5Nb2Mo2Cu1Si15.5B7 at.% nanocrystalline soft magnetic ribbon was stress-annealed at several temperatures around its primary crystallization temperature and magnetic properties were characterized in strips to determine conditions that led to minimal magnetic coercivity, Hc. This optimal stress-annealing (SA) temperature, though yielding minimal Hc in strips, also produced non-linear or rounded BH loops in wound cores. The rounded loops could be changed to linear or flat B-H loops following a secondary static annealing process. Through X-ray diffraction, transmission electron microscopy, and indirect magnetostriction measurements, we determined that the change in loop shape was driven by additional crystallization and stress-relief from the static annealing process. A change in mechanical properties including fracture toughness, loss modulus, and Young’s modulus after SA, were shown to limit the processability of the ribbon. Tape-wound inductors subjected to the optimal 640 °C / 85 MPa / 4 s SA process followed by a static annealing treatment of 500 °C for 1 h resulted in flat loops, an Hc of 0.3 A/m, low magnetostriction of ∼ 2 ppm, and core losses of only 7 W/kg at an induction of 0.4 T when excited at 20 kHz.

Microstructure evolution, stress state and electromagnetic performance of Fe-based nanocrystalline alloy induced by stress-annealing

Stress-induced anisotropy has been applied for FeSiBCuNb nanocrystalline alloy ribbons in transformers with large direct current (DC) component. However, the physical mechanism of anisotropy induced by stress annealing during crystallization remains controversial. Here, a systematic study was conducted on the microstructure, residual stress state, dynamic domain structure and properties of the stress-annealed FeSiBCuNb nanocrystalline ribbons. Present results demonstrate that, the increase of the applied stress greatly increases the residual tensile stress and induces lattice distortion, which acts as pinning site during magnetization, resulting in enhanced domain-wall energy and narrower wall width. Meanwhile, stress annealing promotes the flattening of hysteresis loops and decreases the effective permeability, which improves the DC-bias characteristics of the ribbons, thereby promoting the transition from “hard saturation” to “soft saturation” behavior. Also, stress-induced grain refinement is beneficial to obtaining high hardness. Owing to the stress-induced anisotropy, the stress-annealed sample with applied stress of 113 MPa exhibits excellent combined properties, including low constant effective permeability of 438 at wide frequency range (1 kHz–8 MHz), high DC-bias capability of 74% (30 Oe), low power loss of 49 kW/m3 (100 mT, 100 kHz), and high hardness of 644 HV. This discovery provides an insightful understanding of stress-induced anisotropy mechanism on the high-performance Fe-based nanocrystalline alloys.

Amorphous ribbons for GMI detection of stray fields FeOx magnetic filler of epoxicomposites

Magnetoimpedance (MI) effect in stress-annealed Co-based amorphous ribbon was studied in the states without and in presence of the magnetic epoxy composite of cylindrical shape. Iron oxide FeOx magnetic microparticles of different concentrations (0–70 wt.%) were used as a magnetic filler. The condition of stress annealing (350 °C, 1 h and 250 MPa specific load) were selected in order to insure the high MI sensitivity with respect to external magnetic field in the field of a few Oersted. The MI responses were modified in the presence of the magnetic epoxy composites due to the contribution of the stray fields of embedded microparticles. It was experimentally found that degree of the MI curves modification depended on the microparticles concentration. The MI characteristics were also dependent on the length-to-width ratio of the MI element. The most sensitive MI element under study showed a linear dependence with a 1 %/weightpercent microparticle concentration slope. Mathematical modeling using finite elements (FEM) protocol for the properties of short MI elements confirmed the results and highlighted the non-monotonic contribution of high-concentration composites to the MI responses.

Domain wall dynamics in stress annealed microwires

In this work we investigate the effect of stress-annealing on the magnetic properties and domain wall dynamics of CoFeNi-based microwires with nearly-zero magnetostriction. Among the annealing parameters whose influence we studied are time and temperature, as well as the magnitude of the stresses applied during annealing. We demonstrate that heat treatment and stress application have the opposite effects on the switching field and domain wall mobility. Therefore, their combination can be used to tune the parameters of the domain wall dynamics over the wide range. We found that stress annealing can increase the domain wall mobility by up to 3 times comparing to annealing without any stress. The maximum domain wall mobility achieved for the studied microwire is 95 m2/sA.

Optimization of Giant Magnetoimpedance Effect of Amorphous Microwires by Postprocessing

Magnetic microwires with amorphous structures can present a unique combination of excellent magnetic softness and giant magnetoimpedance (GMI) effects together with reduced dimensions and good mechanical properties. Such unique properties make them suitable for various technological applications. The high GMI effect, observed in as-prepared Co-rich microwires, can be further optimized by postprocessing. However, unexpected magnetic hardening and a transformation of the linear hysteresis loop into a rectangular loop with a coercivity on the order of 90 A/m were observed in several Co-rich microwires upon conventional annealing. Several routes to improve magnetic softness and GMI effect in Fe- and Co-rich magnetic microwires are provided. We observed that stress annealing could remarkably improve the magnetic softness and GMI ratio of Co-rich microwires. Thus, almost unhysteretic loops with a coercivity of 2 A/m and a magnetic anisotropy field of about 70 A/m are achieved in Co-rich microwires stress annealed at appropriate conditions. The observed change in hysteresis loops and the GMI effect is explained by stress-annealing-induced anisotropy, which is affected by the stresses applied during annealing and by the annealing temperature. While as-prepared Fe-rich amorphous microwires present a low GMI effect, appropriate postprocessing (annealing and stress annealing) allows for a remarkable GMI ratio improvement (an order of magnitude). The evaluated dependence of the maximum GMI ratio on frequency allows the identification of the optimal frequency band for the studied samples. The origin of stress-annealing-induced anisotropy and related changes in hysteresis loops and the GMI effect are discussed in terms of the relaxation of internal stresses, “back-stresses”, as well as structural anisotropy.

Stress Annealing Controlling the Response of the Toroidal Core to Current

Stress Annealing Controlling the Response of the Toroidal Core to Current

Microstructure and mechanical properties of a modified 316 austenitic stainless steel alloy manufactured by laser powder bed fusion

A 316 austenitic stainless-steel alloy, with modified alloy composition, manufactured by laser powder bed fusion (L-PBF) has been investigated. The modification of the alloy composition included addition of niobium (Nb), tungsten (W) and copper (Cu), together with a reduction in the amount of molybdenum (Mo) and an increased amount of carbon (C). To find suitable process parameters, a parameter study by varying laser power, hatch distance and scan speed was performed, centered on typical parameters used for normal 316 L. As-built material from a selected parameter configuration was then subjected to different stress relief annealing heat treatments and ageing heat treatments. The effectiveness of the stress annealing was ranked using a deformation-based method. Microstructural characterization, hardness and room temperature tensile testing were done to evaluate the effect of stress relief and aging heat treatments.It was found that a higher volumetric energy was needed to build dense material, about ∼50 % higher compared to the volumetric energy input for normal 316 L. A subsequent aging heat treatment at 725 °C for 3 h increased the strength and hardness of the material. A reinforcement of the cellular microstructure by precipitation of carbides in between the cells is believed to be the main reason for this. To completely alleviate the residual stresses it was necessary to carry out a stress relief annealing process at 950 °C, which resulted in a removal of the cellular structure and a lower strength material.

Effects of drawing and tension stress annealing on the structure and magnetic properties of Co-based amorphous wire

Cold drawing significantly improves the size uniformity of the amorphous wire, but leads to wire curling. Tensile stress annealing (TSA) is the key to regulating the straightness and magnetic properties of Co-based amorphous wires, but their intrinsic correlation is still unclear. Herein, the effects of TSA on the morphology, microstructure, soft magnetic properties and longitudinal driven giant magneto-impedance (LD-GMI) effect of cold drawn Co-based amorphous wires have been studied in detail. It was found that increasing tensile stress can effectively straighten the drawn amorphous wire, yet at the cost of decreasing fracture strength, increasing coercivity and deteriorating GMI effect. Furthermore, appropriate annealing can restore the magnetic properties of the TSA amorphous wire. The variation of magnetic properties is relative to the change of circular anisotropic field and magnetic domain structure.

Stress-annealing induced quasistatic creep recovery in ZrCuAlNi metallic glass

The relationship between the structural relaxation of metallic glasses and their heterogeneous structure, characterized by a weakly bonded region and a strongly bonded region, remains ambiguous. Thus, our study aimed to explore the connection between the heterogeneous structure and structural relaxation by investigating the quasi-elastic and viscoelastic behavior of a Zr55Cu30Ni5Al10 metallic glass. Stress-annealing (SA) treatment was employed to retain elastic strain energy by subjecting the sample to constant stress and temperature. During the reheating of the SA-treated sample, we observed a unique shrinkage and elongation phenomenon in the glassy-solid region, known as creep recovery (CR). To qualitatively describe the mechanisms of elastic strain energy retention and release, we employed the Maxwell model, which accounts for the heterogeneous structure. The residual elastic strain energy was determined by the discrepancy in relaxation ability within the heterogeneous structure, and the shrinkage and elongation of the CR were associated with structural relaxation.

Correlation between stress relaxation induced anisotropy, magnetic domain, and permeability of Co-doped FeCuSiBNbMn alloys

The effect of Co contents on the permeability, magnetic anisotropy, and structure has been investigated for FeSiBNbCuMn amorphous alloys during annealing with and without tensile stress. Large stress relaxation-induced anisotropy (Ku) of 482.0–1485.4 J/m3 is observed with an easy axis perpendicular to the direction of tensile stress (i.e., ribbon axis), which results in constant permeability of 1–2.8 × 103 at 1 kHz − 1 MHz. Different from the irregular domain structure in the samples annealed without tensile stress, stress annealing generates regular domains and 180° straight walls, and domain width increases with the increases of Co contents. Besides, the correlation between permeability, induced anisotropy, and domain width is established. These results could provide a good guide for improving the frequency stability of permeability by adjusting anisotropy and domain structure.

Effect of post-weld heat treatment on mechanical properties and microstructure in electric arc welded mild steel joints

Mechanical and microstructure properties of weld joint between mild steel plates before and after heat treatment process have been studied. In this study, electric arc welding was used as a welding method as it is the most common welding method. Then heat treatment of the samples were done in the furnace. Firstly, in the heat treatment process, stress annealing was done as stress generated at different places in the welding zone and after that full annealing was done using furnace cooling for cooling purpose. Tensile strength was measured using ASTM A370 standard specimen and Brinell hardness test was done at different surfaces of the welding zone. The microstructures were observed by cutting the specimen in a certain shape, and mirror surfaces were generated to observe in electron microscope. From the results, it was observed that PWHT causes a 4.1 % increase in tensile strength, a 13.84 % gain in yield strength, and a 4.96 % rise in percentage elongation. However, the value of hardness decreased 19.19 % after heat treatment as heat treatment increased the ductility of the specimen. At the place of the Electric Arc Welding joint, a smaller grain size, a lower gap between the grains, and comparatively few voids were identified.

The effect of electrical stress and thermal annealing on swift heavy ion irradiated SiGe HBTs

The nano-engineered silicon–germanium heterojunction bipolar transistors (SiGe HBTs) were irradiated with 100 MeV phosphorous ions up to a high total dose of 100 Mrad. The irradiated SiGe HBTs were subjected to mixed mode (MM) electrical stress and isochronal annealing. The DC electrical characteristics were studied for ion irradiated, electrically stressed and thermally annealed SiGe HBTs. The important parameters such as base current (IB), current gain (hFE) and output characteristics of the irradiated SiGe HBTs were significantly degraded after 100 Mrad of the total dose. This is due to high energy ion induced damages in Emitter-Base (E-B) and Shallow Trench Isolation (STI) oxides. A significant recovery in device parameters was observed after both MM stress and isochronal annealing. The recovery in electrical characteristics of the irradiated SiGe HBTs is mainly due to the raise in the junction temperature and de-trapping of trapped charges.

Anomalous Nernst Effect in Flexible Co-Based Amorphous Ribbons.

Fe3Co67Cr3Si15B12 ribbons with a high degree of flexibility and excellent corrosion stability were produced by rapid quenching technique. Their structural, magnetic, and thermomagnetic (Anomalous Nernst Effect) properties were studied both in an as-quenched (NR) state and after stress annealing during 1 h at the temperature of 350 °C and a specific load of 230 MPa (AR). X-ray diffraction was used to verify the structural characteristics of our ribbons. Static magnetic properties were explored by inductive technique and vibrating sample magnetometry. The thermomagnetic curves investigated through the Anomalous Nernst Effect are consistent with the obtained magnetization results, presenting a linear response in the thermomagnetic signal, an interesting feature for sensor applications. Additionally, Anomalous Nernst Effect coefficient SANE values of 2.66μV/K and 1.93μV/K were estimated for the as-quenched and annealed ribbons, respectively. The interplay of the low magnetostrictive properties, soft magnetic behavior, linearity of the thermomagnetic response, and flexibility of these ribbons place them as promising systems to probe curved surfaces and propose multifunctional devices, including magnetic field-specialized sensors.

The effect of stress-annealing on the mechanical and magnetic properties of several Fe-based metal-amorphous nano-composite soft magnetic alloys

Fe-based metal-amorphous nanocomposites (MANCs) are the subject of many contemporary studies for their unique tunable soft-magnetic properties. The alloys can exhibit some of the smallest losses and highest power storage capabilities of available materials used in electromagnetic inductors. Here, the magnetic and mechanical properties of Fe72.5Nb2Mo2Cu1Si15.5B7 at.%, Fe68.5Co5Ta3Cu1Si16.5B6 at.%, Fe68.5Co5Ta3Cu1Si16B6.5 at.%, and Fe73.5Ta3Cu1Si16B6.5 at.% melt-spun alloys were investigated in relation to their ability to be stress-annealed to tune permeability while simultaneously minimizing losses in tape-wound inductor cores. Mechanical and physical properties of the as-cast and processed ribbons including relaxation and crystallization temperatures and failure strains were measured using thermomechanical analysis (TMA), uniaxial tension, and bend tests to help inform the stress-annealing parameters. Magnetic properties were measured for the as-cast and stress-annealed materials in both wound-cores and flat ribbon strips. The alloys exhibited severe embrittlement during heating, thus creating significant challenges when tuning magnetic properties with an in-line stress-annealing (SA) process. However, when conditions were optimized, core losses as low as 1.14 W·kg−1 were obtained when cores were excited at 10 kHz to a maximum induction field of 0.1 T, which are among the lowest reported in the literature. Based on this preliminary effort, understanding of the stress state in amorphous precursor ribbons prior to SA could reveal the key to developing more robust in-line SA processes for brittle Fe-based MANCs.

Types and origin of surface defects induced by post-growth annealing of CdZnTe and CdMnTe crystals

In this paper, several kinds of defects induced by post-growth annealing were studied. The type, morphology, origin and formation mechanism of these defects were analyzed and discussed. The defects were characterized by a number of testing methods. The results indicated that high temperature (>973 K) and long time (240 h) annealing were harmful to CdZnTe and CdMnTe crystals, which led to thermal etch pit and surface and internal oxidation. The phenomena of thermal migration of Te inclusions and integration of precipitate/inclusion were observed during isothermal annealing with lower temperature (773–873 K) and shorter time (15–60 h). Stress, atmosphere and temperature gradient annealing were main factors for induced defects such as crack, warping, bulge and Zn-related defect. In order to avoid these defects, suitable annealing source and atmosphere for crystals of different properties, high vacuum annealing quartz tube, optimized annealing temperature and time, smaller temperature gradient and multiple annealing methods were proposed. The research would be helpful for crystal growth and post-growth annealing of CdTe-based semiconductor materials.

Facile and Scalable Fabrication of High-Performance Polylactide-Based Medical Microparts through Combining the Microinjection Molding Intense Shear Stress Field and Annealing Strategy

Facile and Scalable Fabrication of High-Performance Polylactide-Based Medical Microparts through Combining the Microinjection Molding Intense Shear Stress Field and Annealing Strategy

Recovery of LED Emission Power under the Exposure to γ-n-Pulse

The article presents results of the study of the effect of LED power modes based on AlGaAs heterostructures (short-circuit, open circuit, and active mode with the passage of operating current during irradiation) on the resistance to γ-n-pulse exposure. Reduction of LED emission power under the influence of γ-n-pulse occurs in two stages irrespective of irradiation power mode, with each stage characterized by its own regularity and its own factor. Built-in electric field of p-n-junction does not contribute significantly to the degradation of LED power when exposed to γ-n-pulse. At irradiation of LED in active power mode after exposure to γ-n-pulse (Fn ≤ 1.5·1012n/cm2, Dγ ≤ 20 Gy (Si)) a recovery of LED power by the value of ΔP is observed. Recovery of ΔP power leads to reduction of the damage factor at the first stage, to increase of the LED resistance, and to shift of the boundary between the stages to the area of higher neutron fluences. It is supposed, that the observed jump-like increase of ΔP radiation power under the influence of γ-n-pulse is caused by radiation-stimulated annealing of local mechanical stresses that is generated under the condition of passing of operating current through LED.

Additive Manufacturing of AlSi10Mg and Ti6Al4V Lightweight Alloys via Laser Powder Bed Fusion: A Review of Heat Treatments Effects.

Laser powder bed fusion (L-PBF) is an additive manufacturing technology that is gaining increasing interest in aerospace, automotive and biomedical applications due to the possibility of processing lightweight alloys such as AlSi10Mg and Ti6Al4V. Both these alloys have microstructures and mechanical properties that are strictly related to the type of heat treatment applied after the L-PBF process. The present review aimed to summarize the state of the art in terms of the microstructural morphology and consequent mechanical performance of these materials after different heat treatments. While optimization of the post-process heat treatment is key to obtaining excellent mechanical properties, the first requirement is to manufacture high quality and fully dense samples. Therefore, effects induced by the L-PBF process parameters and build platform temperatures were also summarized. In addition, effects induced by stress relief, annealing, solution, artificial and direct aging, hot isostatic pressing, and mixed heat treatments were reviewed for AlSi10Mg and Ti6AlV samples, highlighting variations in microstructure and corrosion resistance and consequent fracture mechanisms.

Stress-accelerated softening in bulk nanocrystalline Mg-Gd-Y-Zr alloys

Exploring the microstructure and mechanical property evolution of metallic structural materials during stress annealing has scientific and engineering significance since these materials are usually used to bear coupled thermo-mechanical loads in their service life. Here, we report a stress-accelerated softening phenomenon in bulk nanocrystalline Mg-Gd-Y-Zr alloys. Transmission electron microscopy observation indicates that, compared with static annealing, stress annealing accelerates the grain coarsening and precipitation of the grain boundary β phases. The precipitation of β phases results in the depletion of intragranular solute atoms, which therefore weakens the solid solution strengthening effect. The stress-assisted β phase precipitation and grain coarsening lead to the accelerated softening of nanocrystalline Mg-Gd-Y-Zr alloys. That is, the mechanical properties of nanocrystalline Mg-Gd-Y-Zr alloys subjected to coupled thermo-mechanical loads deteriorate more rapidly compared with the statically-annealed alloys.