Surface Mechanical Attrition Treatment Research Articles

Investigation of Mechanical Properties and Microstructural Evolution in Pure Copper with Dual Heterostructures Produced by Surface Mechanical Attrition Treatment

Heterostructured materials consist of heterogeneous zones with dramatic variations in mechanical properties, and have attracted extensive attention due to their superior performance. Various heterostructured materials have been widely investigated in recent years. In the present study, a combination of two different types of heterogeneous structures, a surface bimodal structure and gradient structure, was designed using the traditional surface mechanical attrition treatment (SMAT) method in pure copper, and the mechanical properties and microstructural evolution of dual-heterostructure Cu were studied in depth. In total, 100 stainless steel balls with a diameter of 6 mm were utilized to impact the specimen surface at room temperature for a short period of time. In this work, the sample surface was divided into hard areas and soft areas, along with a roughly 90 μm gradient structure in the cross-sectional direction after 30 s of SMAT processing. After the partial SMAT processing, lasting 30 s, the strength increased to 158.0 MPa and a considerable ductility of 25.7% was sustained, which overcomes the strength–ductility trade-off. The loading–unloading–reloading (LUR) test was utilized to measure the HDI stress, and the result showed that the HDI stress of the partial SMAT sample was much higher than the annealed one, especially for the Cu-SMAT-30S specimen, the strength of which increased from 80.4 MPa to 153.8 MPa during the tensile test. An in situ digital image correlation (DIC) investigation demonstrated that the strain developed stably in the Cu-SMAT-10S specimen. Furthermore, electron backscatter diffraction (EBSD) was carried out to study the microstructural evolution after partial SMAT processing; the KAM value increased to 0.34 for the Cu-SMAT-10S specimen. This research provides insights for the effective combination of superior strength and good ductility in dual-heterostructure materials.

Improving Corrosion Resistance of Low Carbon Steel through Surface Mechanical Attrition Treatment Duration

Improving Corrosion Resistance of Low Carbon Steel through Surface Mechanical Attrition Treatment Duration

Enhancing mechanical properties and wear resistance of dual phase steel through surface mechanical attrition treatment

The study investigates the mechanical properties of dual-phase (DP) steel undergoing surface martensite transformation through Surface Mechanical Attrition Treatment, revealing phase transformation and grain refinement, increasing exponentially with treatment duration. After 40 min of SMAT, X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) analyses revealed approximately 37% martensite and 63% ferrite phases, in contrast to 5% martensite and 95% ferrite phases in the as-received state. The surface hardness of the steel increased to 270 VH0.05 (up from 145 VH0.05), while the yield strength rose to 405 MPa (up from 258 MPa). Furthermore, a 60% reduction in the specific wear rate of the steel was achieved. This study highlights SMAT as an innovative method for tailoring the microstructure of steel and enhancing its mechanical properties through stress-induced phase transformation.

Role of nanostructured surface layers in enhancing pure titanium diffusion bonding above their destabilization temperatures

The benefits of the nanostructured materials are believed to be probably absent if they are used at high temperatures. In this study, enhanced diffusion bonding of pure Ti was investigated by introducing a nanostructured surface layer through the surface mechanical attrition treatment (SMAT) technique. Complete recrystallization and remarkable grain growth have taken place in the original nanostructured surface layer due to the diffusion bonding conditions far beyond the nanostructured Ti destabilization temperatures. However, they still played a significant role in enhancing the Ti/Ti interfacial bonding. The consistency analysis of relative grain boundary energy, relaxation time, and microstrain reveals that although the original nanocrystalline has disappeared, the newly formed grain boundaries (GBs) during recrystallization probably inherit part of non-equilibrium state of the corresponding GBs in the as-SMATed surface layer, where the atomic diffusivity may increase greatly compared to the general relaxed GBs in their coarse-grained polycrystalline counterparts. The presence of these high-energy non-equilibrium GBs retains ultrafast atomic diffusion paths, leading to a diffusion bonding temperature of at least 100 °C lower than the traditional approach. The joint achieved at a low temperature of 750 °C exhibited a shear strength approximately 2 times higher than that prepared using raw substrates.

Investigating microstructure dynamics and strain rate sensitivity in gradient nanostructured AISI 304 L stainless steel: TEM and nanoindentation insights

In recent years, gradient nanostructured (GNS) materials have gained significant attention due to their superior strength-ductility balance and enhanced functional properties compared to their coarse-grained counterparts. This research examines the microstructure evolution and nanomechanical responses of GNS AISI 304 L austenitic stainless steel using transmission electron microscopy (TEM) and nanoindentation techniques. Through surface mechanical attrition treatment (SMAT), a gradient nanostructured layer with ultrafine grains (∼15 nm) and nanoscale martensite (up to ∼40 %) within the austenite matrix has been successfully created on the steel’s surface. This treated surface exhibits a hardness of ∼6.7 GPa, nearly double the original value. The GNS layer demonstrates single-step (γ → α’) and two-step (γ → ε → α’) martensitic transformations, deformation twinning (γ -twin), a decrease in the density of deformation bands, compressive residual stress, lattice strain, and martensite content, along with an increase in grain size. Strain rate sensitivity (SRS) increases with austenitic grain size and inversely correlates with martensite proportion as depth increases in the GNS layer. A significant amount of ultrafine martensite is primarily responsible for the limited SRS in the topmost layer.

Investigation of mechanical and wettability properties of commercial pure titanium by surface mechanical attrition treatment

The examination of mechanical and wettability properties of commercial pure titanium (CP-Ti) introduced a novel challenge. The microstructure of samples was analyzed by using OM and SEM micro-images. In this study, the hardness of the surface and cross section of samples was evaluated, and the effect of several surface mechanical attrition treatments (SMATed) on samples was examined. Also, the tensile test was done to compare the effect of SMAT duration on mechanical properties of samples. The contact angle method was then employed to investigate the impact of SAMT duration on the wettability trend. According to results, as the treatment time increases, twins become evident in the deeper layers of the samples. In contrast, the near-surface twins are shorter than those found in the deeper material, signifying the presence of finer grains. Moreover, the elevated hardness in SMATed samples can be attributed to several key factors, including cold work, a rise in defects and twins, and grain refinement. The surface hardness increases across the sample series (up to Ti6) due to the substantial energy input. Nevertheless, it is anticipated that further continuation of the process will result in a constant surface hardness. The increased strength observed in SMATed samples can be attributed to factors such as reduction in grain size and the formation of twins. The wettability results show that the treated surfaces exhibited a significant change in wettability compared to the untreated samples, with a 25% reduction in the contact angle. This is attributed to the surface modifications induced by the treatment process, which introduced more hydrophilic functional groups. The results also show that after 4 h of treatment, the contact angle increases, suggesting that the trend may plateau with additional treatment time.

The Influence of Surface Nanocrystallization of TA2 Titanium Alloy on Its Corrosion Resistance

In this study, the surface nano treatment of TA2 titanium alloy was realized by means of surface mechanical wear treatment. The microstructure and electrochemical properties of the nanocrystalline layer were investigated by SEM, TEM, Electrochemical Impedance Spectroscopy, and Potentiodynamic Polarization, while the nucleation mechanism of the passivation film was discussed. The results indicate that the original coarse grains on the sample’s surface are transformed into randomly oriented nanocrystals by surface mechanical attrition treatment (SMAT). The corrosion current density of the surface nanocrystallized TA2 titanium alloy (9.2 nA·cm−2) experienced a reduction of two orders of magnitude compared to untreated TA2 titanium alloy (134.5 nA·cm−2) in 3.5 wt.% NaCl solution. The SMAT methods accelerates nucleation mechanism transitioning to continuous nucleation.

Enhanced tribological properties and the microstructure evolution of the gradient nanostructured copper alloy

In this work, the effects of the gradient microstructures by surface mechanical attrition treatment (SMAT) on the corresponding tribological properties of the nanoprecipitates strengthened copper alloy was investigated. The nanoprecipitates strengthened copper alloy possesses a decent tribological properties compared with the pure copper and bronze. The SMAT-processed NP&T alloy possesses distinctly lower coefficients of friction (COF) than its coarse-grained counterpart throughout the entire frictions. In particular, under a sliding load of 2 N, NP&T alloy possesses a lower COF of 0.58 ± 0.03, approximately 15% lower than that of its homogeneous counterpart. Additionally, the wear volumes, wear rates, and worn surface roughness were approximately 45% lower in the NP&T alloy, indicating the superior tribological properties. The macro-, micro-, and atomic-scale friction and wear mechanisms in the worn NP&T alloy were systematically determined. The inherent gradient nanostructures could achieve strain delocalization, thereby suppressing surface deformation and improving wear resistance. Wear-induced substructure in the NP&T alloy comprises gradient layers mediated by twinning and stacking faults combined with nanocomposite layers, resulting in novel tribological performance characteristics. Thus, combining inherent and newly formed wear-resistant gradient nanostructures is an effective design strategy for high-performance Cu alloys.

Enhancing wear resistance, anti-corrosion property and surface bioactivity of a beta-titanium alloy by adopting surface mechanical attrition treatment followed by phosphorus ion implantation

A two-step method of surface mechanical attrition treatment (SMAT) followed by phosphorous (P) ion-implantation was adopted to treat Ti-25Nb-3Mo-2Sn-3Zr (named as TLM) alloy. The initial SMAT process refined the grains from micrometer-scale to about 10–30 nm, and begot the TLM surface much rougher with apparently improved hydrophilicity. The subsequent P ion-implantation led to the formation of a hybrid structure of the TiP, β-Ti nanograins and P-interstitial amorphous in the surface layer of the TLM alloy, and resulted in a slight decrease of the surface roughness and wettability of the SMAT-processed alloy. The indentation, tribology and potentiodynamic polarization tests indicated that the SMAT procedure concurrently enhanced the microhardness, wear-resisting property and corrosion resistance of the TLM alloy, and the followed P-ion implantation could further improve these tested properties. Moreover, the P-ion implanted TLM alloy was verified to exhibit much better surface bioactivity (including biomineralization in the simulated body fluid (SBF) and in-vitro cell adhesion) as compared to the original TLM alloy. With the remarkable improvements of the wear resistance and anti-corrosion property as well as the surface bioactivity of the P ion-implanted TLM alloy, our study provides an alternative avenue to fabricating new-type Ti-based orthopedic implants with superior comprehensive performance.

Enhanced corrosion fatigue strength of additively manufactured graded porous scaffold-coated Ti-6Al-7Nb alloy

Current modifications of Ti-based materials with porous scaffolds for achieving biological fixation often decrease corrosion fatigue strength (σcf) of the resultant implants, thereby shortening their service lifespan. To resolve this issue, in the present, a step-wise graded porous Ti-6Al-7Nb scaffold was additively manufactured on optimally surface mechanical attrition treated (SMATed) Ti-6Al-7Nb (specifically denoted as S-Ti6Al7Nb) using laser powder bed fusion (PBF) technology. The microstructure, bond strength, residual stress distribution, and corrosion fatigue behavior of porous scaffolds modified S-Ti6Al7Nb were investigated and compared with those of mechanically polished Ti-6Al-7Nb (P-Ti6Al7Nb), S-Ti6Al7Nb, and porous scaffolds modified P-Ti6Al7Nb. Results showed that corrosion fatigue of porous scaffolds modified Ti-6Al-7Nb was propagation controlled. Moreover, the crack propagation behavior in the PBF scaffold's fusion zone (FZ) and heat-affected zone (HAZ), exhibiting insensitivity to the microstructural configurations characterized by columnar prior-β grain (PBG) boundaries and acicular α′ martensites, coupled with the PBF-induced residual tensile stresses in these regions, resulted in a considerable decrease in σcf for porous scaffolds modified P-Ti6Al7Nb compared to P-Ti6Al7Nb. In contrast, step-wise graded porous scaffold-modified S-Ti6Al7Nb demonstrated an improved σcf which was even higher than that of P-Ti6Al7Nb. Such an advancement in corrosion fatigue strength is primarily attributed to the presence of residual compressive stresses within the underlying S-Ti6Al7Nb substrate, extending beyond FZ and HAZ. These stresses increased the crack propagation threshold, leading to crack deflection/branching and increased crack-path tortuosity, thereby synergistically markedly enhancing the crack propagation resistance of porous scaffolds modified S-Ti6Al7Nb.

Ultrahigh fatigue strength of gradient nanostructured plain steel

In light of the steel development trend—plainification and high performance, we designed a gradient nanostructured plain steel with ultrahigh mechanical performance and exceptional cost performance. This multiscale design is achieved by using surface mechanical attrition treatment (SMAT) in a plain steel matrix subjected to quenching-partitioning-tempering (Q-P-T) process. The integration of Q-P-T and SMAT processes effectively achieves the gradient surface nanocrystallization on the high mechanical performance matrix. This gradient nanostructure exhibits an environment with gradient compressive stress accompanying with the refinement of grains, which prevent crack formation and propagation effectively. Consequently, an ultrahigh fatigue strength (up to 820 MPa) at high-cycle (107) can be achieved with remarkable cost performance (1653.1 MPa·kg/USD) at the same time, surpassing maraging steel by 14 times. The multiscale design of gradient nanostructured plain steel not only breaks the endurance-cost trade-off but also paves the way to imparting significant endurance on high carbon plain steel.

Analysis of the effect of surface mechanical attrition treatment on the mechanical properties of 17-4 PH stainless steel obtained by material extrusion

Analysis of the effect of surface mechanical attrition treatment on the mechanical properties of 17-4 PH stainless steel obtained by material extrusion

Superior strength and wear resistance of mechanically deformed High-Mn TWIP steel

In the present study, the mechanical and wear behaviour of the surface-mechanically treated high-manganese (high-Mn) twinning-induced plasticity (TWIP) steel were investigated. The TWIP alloy was first designed and fabricated via surface-mechanical attrition treatment (SMAT) system and the mechanical properties including strength, wear behaviour as well as the microstructural evolution were thereafter determined. Transmission electron microscopy (TEM) characterization revealed a typical dislocation as a result of the surface treatment as well as the formation of twin layers with a reduced stacking fault energy (SFE). Due to the ultra-fine grain refinement caused by plastic deformation during surface treatment, a microhardness value of 489 HV can be obtained after treatment. Likewise, the yield strength of the high-Mn TWIP steel could be enhanced from 360 MPa to 813 MPa and a reduction in elongation to failure of about 20 % can be achieved. The wear test showed that the treated TWIP steel possessed a reduced friction coefficient and improved wear resistance at different testing loads, attributed to the nanoscale refinement of grains induced during treatment. The strength, hardness, and wear resistance of the fabricated TWIP alloy improves significantly, thanks to surface treatment by SMAT.

Influence of Surface Mechanical Attrition Treatment Parameters on the Residual Stress of EN8 Steel

Influence of Surface Mechanical Attrition Treatment Parameters on the Residual Stress of EN8 Steel

Enhancing steel properties with surface mechanical treatments

This research presents the modification of the microstructure on the surface of a dual phase steel (DP) using three different treatments: surface mechanical attrition treatment (SMAT), surface mechanical carburizing treatment (SMCT), and surface mechanical composite coating treatment (SMCCT). We used SMAT to refine the grain size under high strain and strain rate conditions and successfully induced a phase transformation to martensite. The introduction of carbon during SMAT resulted in surface mechano-chemical carburizing, which enhanced the martensite transformation. Furthermore, the addition of silicon during the process led to the formation of SiC and Fe3C particles dispersed within the ferrite and martensite matrix, creating a surface nano-composite. Analysis using SEM and XRD revealed that the carbon and silicon-treated steel exhibited 41.4% martensite, 4.4% bainite, and 54.1% ferrite, indicating increased transformation by these elements. As a result, the alterations in the surface microstructure led to changes in the mechanical properties of the DP steel. Initially, the DP steel had Y.S. of 250 MPa and U.T.S. of 350 MPa. After SMAT treatment, its Y.S. and U.T.S. increased to 280 MPa and 380 MPa, respectively. The addition of carbon and silicon further enhanced the Y.S. and U.T.S. to 350 MPa and 450 MPa. A significant change in microhardness is achieved from 150HV0.05 to 255HV0.05 while after SMCT and SMCCT is 275HV0.05. Despite an increase in surface roughness contributing to heighten friction, there was a significant reduction in wear. This phenomenon could be attributed to grain refinement, dislocation structures, and martensite phase transformations associated with surface hardening.

Microstructural and electrochemical behaviour of severely surface-deformed 316L steel manufactured by conventional and selective laser melting routes

This study thoroughly examines the influence of conventional and selective laser melting (SLM) routes and surface mechanical attrition treatment (SMAT) on the microstructural and electrochemical properties of 316L steel. Compared to wrought specimens, the SLM specimens exhibit significantly smaller grains (∼41 vs. ∼83 µm) and higher dislocation density (∼7.2 × 1013 vs. ∼3.7 × 1012 m−2). Both specimens show nearly doubled surface hardness after SMAT, with the SLM surface displaying a ∼30 nm grain size and minimal α’ phase. The microstructure significantly influences passivation and corrosion behaviour. The SLM specimens exhibit superior electrochemical characteristics to wrought counterparts in SMATed (0.00299 mmpy) and non-SMATed (0.00771 mmpy) conditions. SMAT effectively eliminates surface porosity, enhancing the passivation and corrosion resistance of SLM steel.

Enhancing wear resistance of aluminum alloy by fabricating a Ti-Al modified layer via surface mechanical attrition treatment

The limited wear resistance of aluminum alloys hinders their application in lightweight equipment. Herein, we present the successful fabrication of a Ti-Al modified layer on the surface of aluminum alloy 2024 via surface mechanical attrition treatment (SMAT-Ti). Tribological assessments indicate an improvement in tribological performance. Specifically, the average friction coefficient and wear rate of the SMAT-Ti treated sample decreased by 49.1% and 81.9%, respectively, compared to untreated sample. Analysis of wear surfaces and molecular dynamics simulations demonstrate that the improvements observed can be attributed to the wear-resistant tribofilm formation. Furthermore, the integration of Ti particles beneath the subsurface facilitates the formation of HCP bands and dislocation locks. These microstructural changes obstruct frictional shear deformation and crack propagation, effectively reducing wear.

Phase field study on phase stability at high temperatures in nanograined Fe–Ni alloy prepared by plastic deformation

The phase stability at high temperatures in nanograined Fe–Ni alloy prepared by surface mechanical attrition treatment (SMAT) and ball milling (BM) modes are drastically different. For example, the onset temperature (As) of reverse martensitic transformation (RMT) of nanocrystal prepared by SMAT is higher than that of coarse crystal, while BM exhibits the opposite result. The elastoplastic phase field model for RMT was first proposed to investigate the correlation between RMT and its forward martensitic transformation (FMT), in turn, the above experimental phenomena were revealed in this paper. The prepared nanocrystals with the same diameter (15 nm) by SMAT and BM mode were taken as representative examples. The simulation results indicated that the strain energy is relaxed by the applied strain during FMT in nanocrystalline prepared by smaller plastic deformation mode (e.g. SMAT), but it is enhanced by larger plastic deformation mode (e.g. BM). The stored strain energy in BM mode is much larger than that in SMAT mode, and hence the driving force provided for subsequent RMT is also larger in BM mode. Therefore, the phase stability of the martensitic nanocrystals prepared by BM mode at high temperatures is much lower than the counterpart by SMAT mode, which agrees well with the experimental measurements.

New method for position and energy controlled surface mechanical attrition treatment and its effects in 304 stainless steel

New method for position and energy controlled surface mechanical attrition treatment and its effects in 304 stainless steel

Nickel-based superalloy architectures with surface mechanical attrition treatment: Compressive properties and collapse behaviour

Surface modifications can introduce natural gradients or structural hierarchy into human-made microlattices, making them simultaneously strong and tough. Herein, we describe our investigations of the mechanical properties and the underlying mechanisms of additively manufactured nickel–chromium superalloy (IN625) microlattices after surface mechanical attrition treatment (SMAT). Our results demonstrated that SMAT increased the yielding strength of these microlattices by more than 64.71% and also triggered a transition in their mechanical behaviour. Two primary failure modes were distinguished: weak global deformation, and layer-by-layer collapse, with the latter enhanced by SMAT. The significantly improved mechanical performance was attributable to the ultrafine and hard graded-nanograin layer induced by SMAT, which effectively leveraged the material and structural effects. These results were further validated by finite element analysis. This work provides insight into collapse behaviour and should facilitate the design of ultralight yet buckling-resistant cellular materials.