Search Results (36)

A microalloyed high-carbon low-alloy steel was designed to clarify the combined effects of austenitizing temperature and deep cryogenic treatment (DCT) on microstructural evolution and mechanical performance. Specimens were austenitized at 770–900 °C, water-quenched, subjected to DCT at −196 °C, and subsequently tempered at 180 °C. Microstructural characterization by XRD, EBSD, and TEM indicates that the quenched microstructure is dominated by martensite and cementite, with retained austenite below 1% at moderate austenitizing temperatures. DCT does not fundamentally alter the martensitic morphology but promotes the transformation of retained austenite and induces substructure fragmentation, dislocation reorganization, and a more homogeneous lattice strain distribution. Concurrently, carbon redistribution during cryogenic exposure facilitates the formation of finely dispersed carbides. After tempering, partial recovery and stabilization of the martensitic substructure lead to reduced lattice distortion while maintaining a high density of effective strengthening features. Mechanical testing shows that DCT combined with appropriate austenitizing (770–790 °C) improves hardness and ultimate tensile strength with acceptable ductility, whereas excessive austenitizing at 900 °C results in severe grain coarsening and intergranular brittle fracture. The results demonstrate that optimized integration of microalloying and DCT enables a favorable strength–toughness balance in high-carbon tool steels. Full article

Aluminium is widely used in electrical and structural applications; however, its lower electrical conductivity compared to copper limits broader adoption in high-performance systems. Deep cryogenic treatment (DCT) and DCT followed by annealing (DCT+A) have recently appeared as promising techniques to refine microstructures and enhance functional properties in metallic materials. In this study, commercially pure aluminium was subjected to DCT and DCT+A with soaking hours of 6, 12, 18, and 24 at −196 °C. The results revealed that both DCT-12 and DCT+A-12 treatments produced significant grain refinement. XRD confirmed the smallest crystallite size (32.39 nm) and maximum dislocation density (9.53 × 10¹⁴ m⁻²) in DCT-12, while extended soaking of 18 h facilitated recovery, yielding larger crystallite sizes (52.82 nm), reduced density, and microstrain. EBSD analysis showed texture strengthening in the (100) and (111) planes and a notable transition from HAGB to LAGB fractions. TEM and Raman analysis further confirmed defect recovery and phonon coherence at longer soaking hours. Electrical conductivity and mobility were enhanced across all treated specimens, with peak values seen for DCT-18 (4.91 × 10⁷ S/m, 50.8 cm²/V·s) and DCT+A-18 (4.52 × 10⁷ S/m, 46.9 cm²/V·s). These findings confirm that 18 h of soaking is optimal, particularly when combined with annealing, and yields a stable microstructure, improved electron transport, and superior conductivity. Full article

T6 aging, involving solution treatment and artificial aging, is a widely adopted strengthening method for magnesium alloys due to its proven effectiveness. However, the integration of three or more sequential thermal treatments has been explored only sparingly, primarily due to the challenges associated with optimizing such multi-parameter processing systems. This study demonstrates that integrating a 12 h deep cryogenic treatment (DCT) before aging in a Mg–Al–Ca–Mn alloy optimizes mechanical performance, achieving a tensile strength of 343 MPa and 27.3% elongation. Microstructural analysis, based on electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM), reveals that the strength enhancement results from ~29 nm precipitate refinement, elevated dislocation density, and nanoscale sub-grain formation, while the ductility gains stem from the activation of non-basal slip systems and the suppression of microcrack propagation. These synergistic mechanisms enable superior strain accommodation, providing a clear framework for DCT-enabled sequential heat treatment design in high-performance magnesium alloys. Full article

The tension behaviors of Al-Mg alloys were tested, and the influences of deep cryogenic treatment (DCT) and grain size on their tensile properties were explored. Optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the evolution of the microstructure. It was concluded that the alloys with fine grain (FG) had a higher strain hardening capacity and strength, however, the alloys with coarse grain (CG) exhibited better plasticity. This can be explained by the alloy with fine grains having a higher density of grain boundary, which can hinder the motion of the dislocation; therefore, the deformation resistance was improved. For alloys with coarse grains, the dislocation has more freedom to move and is easier to rearrange, which is beneficial to the plasticity. Moreover, when given deep cryogenic treatment, the strength and plasticity of the alloys can be slightly improved, which can be attributed to the microplastic deformation that occurs during cryogenic treatment that can induce internal stress, as cold-induced internal stress is conductive in achieving a finer grain and higher density of dislocation. Full article

In this study, deep cryogenic treatment (DCT) was applied to cold work tool steels with different vanadium weights (Vanadis 4 and Vanadis 10) for 12, 24 and 36 h, and the changes in their mechanical properties and microstructures were examined. Compression, tensile, hardness, SEM–EDS, carbide size, XRD and Rietveld analyses were performed to examine the mechanical and microstructural properties of the cryogenically treated samples. In this study, increasing the cryogenic treatment time and vanadium weight ratio did not have a positive effect on the hardness, and it was determined that the most positive result in terms of tensile and compressive strength was obtained in the V4_DCT-24 sample. The results of this study showed that the cryogenic treatment formed secondary carbides, vanadium carbide (VC) and chromium carbide (Cr₇C₃), in vanadium cold work tool steels and reduced the amount of retained austenite (γ-Fe), transformed into martensite (α’-Fe) structures. Additionally, cryogenically treated Vanadis steels are thought to be usable in the metal processing industry, especially for cutting tools and molds. Full article

The extensive use of copper in thermal and electrical systems calls for constant performance enhancement by means of innovative material treatments. The effects on the microstructural, mechanical, and electrical characteristics of copper in deep cryogenic treatment (DCT) and deep cryogenic treatment followed by heat treatment (DCT + HT) are investigated in this work. Copper samples were treated for various soaking durations ranging from 6 to 24 h. Mechanical properties such as tensile strength, hardness, and wear rate were analyzed. In the DCT-treated samples, tensile strength increased, reaching a peak of 343 MPa at 18 h, alongside increased hardness (128 HV) and a refined grain size of 9.58 µm, primarily due to elevated dislocation density and microstrain. At 18 h of soaking, DCT + HT resulted in improved structural stability, high hardness (149 HV), a fine grain size (7.42 µm), and the lowest wear rate (7.73 × 10⁻¹⁰ mm³/Nm), consistent with Hall–Petch strengthening. Electrical measurements revealed improved electron mobility (52.08 cm²/V·s) for samples soaked for 24 h in DCT + HT, attributed to increased crystallite size (39.9 nm), reduced lattice strain, and higher (111) texture intensity. SEM–EBSD analysis showed a substantial increase in low-angle grain boundaries (LAGBs) in DCT + HT-treated samples, correlating with enhanced electrical conductivity. Overall, an 18 h soaking duration was found to be optimal for both treatments. However, the strengthening mechanism in DCT + HT is influenced by grain boundary stabilization and thermal recovery and is different to DCT, which is strain-induced enhancement. Full article

A novel coupled processing method (PDCT) that associated deep cryogenic treatment (DCT) with a high pulsed magnetic field (PMT) was investigated to improve the performance of an as-cast TC4 aero-titanium alloy. Through XRD, SEM, TEM, EBSD, and a properties test, its microstructure and tensile properties and their relationship were investigated. The results show that in comparison with the untreated samples, in the PDCT alloys, the amount of nano-sized precipitates and dislocation density are increased, and this phenomenon is characterized by their combed dislocation morphology. The grain sizes are refined and rounded, and the deformed grains are enhanced, together with the enhancement of low-angle grain boundaries in grains and the transformation from the β phase to the α phase. The (112) crystal orientation is apparently strengthened. The tensile strength, elongation, and fracture energy of the optimized PDCT sample are 921.4 MPa, 7.6% and 5.47 × 10⁷ J/m³, which increased by 4.9%, 28.8% and 80.5% compared with the untreated sample, respectively. The tensile fracture exhibits rheological deformation along the phase boundaries. The strength–toughness mechanisms are mainly attributed to the texture, precipitation, dislocation and fine grain strengthening, which stem from the cold contraction and lattice distortion of DCT and the main magneto-plasticity effect of PMT, together with their coupling effects. Full article

The objective of this research is to enhance the mechanical and corrosion resistance properties of a cast Ni-Al bronze (NAB). To achieve this, the effect of deep cryogenic treatment (DCT), a process that has shown promise in other alloys, is initially investigated. It is demonstrated that, in the case of NAB, DCT induces only minor microstructural changes, which do not lead to any significant improvement in its properties. Consequently, it is proposed that a combined treatment be employed, involving annealing either before or after DCT. The results indicate that annealing at 675 °C for 2 h following cryogenic treatment at −180 °C increases the yield strength by approximately 11%. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in simulated seawater further confirm that this combination results in the formation of oxide layers with enhanced protective capacity. These improvements are attributed to the significant refinement and homogenization of the microstructure, including the globularization of the kI, kII, and, particularly, kIII phases, and an increase in the precipitation of the kIV phase in a finer and more homogeneous form within the alpha phase. Full article

In recent years, consumers have become increasingly interested in natural, biodegradable and eco-friendly composites. Eco-friendly composites manufactured using natural reinforcing filling materials stand out with properties such as cost effectiveness and easy accessibility. For these reasons, in this research, a composite workpiece was specially manufactured using eco-friendly jute fibers. Two cost-effective cutting tools were specially produced to ensure high-quality machining of this composite workpiece. One of these specially manufactured cutting tools was subjected to DC&T (deep cryogenic treatment and tempering) processes to improve its performance. At the end of the research, when the lowest and highest Fd (delamination factor) values obtained with DC&T-T1 and T1 cutting tools were compared, it was observed that 5.49% and 6.23% better results were obtained with the DC&T-T1 cutting tool, respectively. From the analysis of the S/N (signal-to-noise) ratios obtained using Fd values, it was found that the most appropriate machining parameters for the composite workpiece used in this investigation were the DC&T-T1 cutting tool, a 2000 rev/min spindle speed and a 100 mm/min feed rate. Through ANOVAs (analyses of variance), it was discovered that the most significant parameter having an impact on the Fd values was the spindle speed, with a rate of 53.01%. Considering the lowest and highest Ra (average surface roughness) values obtained using DC&T-T1 and T1 cutting tools, it was seen that 19.42% and 16.91% better results were obtained using the DC&T-T1 cutting tool, respectively. In the S/N ratio analysis results obtained using Ra values, it was revealed that the most appropriate machining parameters for the composite workpiece used in this investigation were the DC&T-T1 cutting tool, a 2000 rev/min spindle speed and a 100 mm/min feed rate. In the ANOVAs, it was revealed that the most significant parameter having an effect on the Ra values was the feed rate at 37.86%. Full article

Deep cryogenic treatment (−196 °C, DCT) is an emerging application that can make significant changes to many materials. In this study, DCT was applied to Ti6Al4V (TC4) titanium alloy, and we delved into an examination of the impact on its microstructural morphologies and mechanical properties. It was observed that DCT has a significant effect on the grain refinement of the TC4 titanium alloy base material. Obvious grain refinement behavior can be observed with 6 h of DCT, and the phenomenon of grain refinement becomes more pronounced with extension of the DCT time. In addition, DCT promotes the transformation of the β phase into the α′ phase in the TC4 titanium alloy base material. XRD analysis further confirmed that DCT leads to the transformation of the β phase into the α′ phase. The element vanadium was detected by scanning electron microscopy, and it was found that the β phase inside the base material had transformed into the α′ phase. It was observed that DCT has a positive influence on the hardness of the TC4 titanium alloy base material. The hardness of the sample treated with 18 h of DCT increased from 331.2 HV_0.5 to 362.5 HV_0.5, presenting a 9.5% increase compared to the sample without DCT. Furthermore, it was proven that DCT had little effect on the tensile strength but a significant impact on the plasticity and toughness of the base material. In particular, the elongation and impact toughness of the sample subject to 18 h of DCT represented enhancements of 27.33% and 8.09%, respectively, compared to the raw material without DCT. Full article

HfNbTaTiZr high-entropy alloy has wide application prospects as a biomedical material, and the use of laser additive manufacturing can solve the forming problems faced by the alloy. In view of the characteristics of the one-time forming of additive manufacturing methods, it is necessary to develop non-mechanical processing modification methods. In this paper, deep cryogenic treatment (DCT) is first applied to the modification of a HEA with BCC structure, then the post-processing method of DCT is combined with laser melting deposition (LMD) technology to successfully realize the coordinated improvement of forming and strength–ductility synergistic improvement in lightweight Hf_0.25NbTa_0.25TiZr alloy. The final tensile strength of the alloy after DCT treatment is 25% higher than that of the as-cast alloy and 11% higher than that of the as-deposited alloy, and the elongation is increased by 48% and 10%, respectively. In addition, DCT also achieves induced phase transition without additional deformation. Full article

Cemented carbide used in the rotor of a mud pulser is subjected to the scouring action of solid particles and corrosive mud media for a long time, which causes abrasive wear and electrochemical corrosion. To improve the wear and corrosive resistance of cemented carbide, samples with different cobalt content (WC-5Co, WC-8Co, and WC-10Co) receive deep cryogenic treatment (DCT) at −196 °C for 2.5 h. An optical metalloscope (OM) and X-ray diffractometer (XRD) are used to observe the phase changes of cemented carbides, and the XRD is also used to observe the change in residual stress on the cemented carbide’s surface. A scanning electron microscope (SEM) is used to characterize the wear and electrochemical corrosion surface microstructure of cemented carbides (untreated and DCT). The results show that the DCT promotes the precipitation of the η phase, and the diffraction peak of $\mathsf{\epsilon }$-Co tends to intensify. Compared with the untreated, the wear rates of WC-5Co, WC-8Co, and WC-10Co can be reduced by 14.71%, 37.25%, and 41.01% by DCT, respectively. The wear form of the cemented carbides is mainly the extrusion deformation of Co and WC shedding. The precipitation of the η phase and the increase in WC residual compressive stress by DCT are the main reasons for the improvement of wear resistance. The electrochemical corrosion characteristic is the dissolution of the Co phase. DCT causes the corrosion potential of cemented carbide to shift forward and the corrosion current density to decrease. The enhancement of the corrosion resistance of cemented carbide caused by DCT is due to the Co phase transition, η phase precipitation, and the increase in the compressive stress of cemented carbide. Full article

Stainless steels are important in various industries due to their unique properties and durable life cycle. However, with increasing demands for prolonged life cycles, better mechanical properties, and improved residual stresses, new treatment techniques, such as deep cryogenic treatment (DCT), are on the rise to further push the improvement in stainless steels. This study focuses on the effect of DCT on austenitic stainless steel AISI 304L, while also considering the influence of solution annealing temperature on DCT effectiveness. Both aspects are assessed through the research of microstructure, selected mechanical properties (hardness, fracture and impact toughness, compressive and tensile strength, strain-hardening exponent, and fatigue resistance), and residual stresses by comparing the DCT state with conventionally treated counterparts. The results indicate the complex interdependency of investigated microstructural characteristics and residual stress states, which is the main reason for induced changes in mechanical properties. The results show both the significant and insignificant effects of DCT on individual properties of AISI 304L. Overall, solution annealing at a higher temperature (1080 °C) showed more prominent results in combination with DCT, which can be utilized for different manufacturing procedures of austenitic stainless steels for various applications. Full article

Medium Mn lightweight steels with a relatively higher Mn content of 9–12 wt% have been actively developed recently to meet the demands of crashworthiness and lightweight vehicles. In this study, a combined intensive quenching (IQ) and deep cryogenic treatment (DCT) was first proposed to achieve the microstructural homogeneity as well as the final strength–ductility synergy of medium Mn lightweight steels with Mn segregation bands, together with a comparison with the conventional intercritical annealing. The proposed IQ and DCT process induced the formation of finer large fractioned plate-like martensite in the austenite matrix and thereby contributed to finer and uniform austenite grains after subsequent intercritical annealing. The martensitic transformation rate (dV_γ/dε) and transformation kinetics (k value) were used to evaluate the mechanical stability of retained austenite, showing that the D700&750 sample exhibited a similar dV_γ/dε value and extremely low k value when compared to the conventional IA650–850 samples, implying that the former had the higher mechanical stability of austenite. The higher mechanical stability of austenite enabled the TRIP effect to occur in a larger strain range, leading to continuous strain hardening behavior. Thus, the highest yield strength (728 MPa) and the largest total elongation of 61.6% were achieved in the D700&750 sample, where the ductility was more than three times higher than that of the conventional IA samples. The grain size and morphologies of retained austenite were believed to be the main factors influencing the strain-hardening behavior of this type of ultrafine lamellar and equiaxed ferrite and austenite duplex structure. Full article

In order to study the effect of the rolling process and aging on the microstructure evolution and mechanical and tribological properties of the material, room-temperature rolling (RTR), cryogenic rolling (CR), and deep cryogenic treatment after rolling (RTR + DCT) experiments were carried out on a Cu-1.0Cr-0.1Zr alloy by a large plastic deformation process. Alloy plates were aged at 550 °C for 60 min. Different rolling processes and aging treatments have different effects on the microstructure and properties of alloy plates. The alloy plate is rolled and deformed, and the grains change from equiaxed to layered. Compared with RTR and RTR + DCT treatment, CR can promote the precipitation of the Cr phase and the degree of grain fragmentation is greater. After aging treatment, the Cu-Zr mesophase compounds in the microstructure increased, the alloys treated with CR and RTR + DCT appeared to be partially recrystallized, and the number of twins in the CR alloy plate was significantly more than that of RTR + DCT. The ultimate tensile strength of the alloy plate reached 553 MPa and the hardness reached 170 HV after cryogenic rolling with 90% deformation, which indicates that CR treatment can further improve the physical properties of the alloy plate. After aging at 550 °C for 60 min, the RTR 90% + DCT alloy plate has a tensile strength of 498 MPa and an elongation of 47.9%, which is three times that of the as-rolled alloy plate. From the research on the tribological properties of alloy plates, we learned that the main wear mechanisms in the wear forms of CR and RTR + DCT alloy plates are adhesive wear and abrasive wear. Adhesive wear is dominant in the early stage, while abrasive wear is the dominant mechanism in the later stage of wear. The friction coefficient of the CR 90% alloy plate in the TD direction is close to 0.55, and the wear rate is 2.9 × 10⁻⁴ mm³/Nm, indicating that the CR treatment further improves the wear resistance of the alloy plates. Full article