Effect of Shot Peening on Surface Characteristics of Ni-Based Single-Crystal Superalloy

The effect of shot peening on surface characteristics of DD3 Ni-based single-crystal superalloy including microstructures, texture and residual stress were investigated, utilizing XRD analysis. Results showed that the polycrystals was introduced into the surface of single-crystal specimen by shot peeing and the initial texture (200) was erased after 60 s-processing. The variation in microstructure was mainly influenced by the processing time and finer domains as well higher microstrain were obtained after 60 s-processing. The value of residual stress depended upon processing time and measurement direction. In the early period of processing (³10 s), residual stress was anisotropy, being significant smaller in h110i direction. With the processing time increased, the anisotropic residual stress gradually changed to isotropic residual stress, due to domainorientation randomization, domain refinement and increase in plastic strain. Also increasing processing time could significantly enhance the magnitude of residual stress and the microhardness. In addition, the influence of processing time on work hardening and residual stress was discussed, based on the deformation mechanism

Finite Element Dynamic Analysis on Residual Stress Distribution of Titanium Alloy and Titanium Matrix Composite after Shot Peening Treatment

The residual stress distribution introduced by shot peening (SP) in the deformed surface layer of Ti-6Al-4V and (TiB+TiC)/Ti-6Al-4V were simulated and studied via the three-dimensional (3D) finite element dynamic analysis and the experimental validation. The program of ANSYS/LS-DYNA was utilized, and the 3D homogeneous and inhomogeneous models were set up. The homogeneous model was established for simulating SP process on Ti-6Al-4V. The influence of three important parameters, the shot balls’ size, shot velocity and coverage rate on residual stress distribution were investigated. Numerical simulation results showed that these parameters contributed different effects on SP treatment. Using a simplified method, an inhomogeneous model for simulating SP process on (TiB+TiC)/Ti-6Al-4V was set up. The max tensile and compressive residual stress (CRS) was +1155 and −1511 MPa, respectively. Based on this stress distribution, the beneficial effect of reinforcements was indicated during deformation, retarding the damage to the matrix and keeping the adverse tensile stresses in the reinforcements. In order to verify the results of simulation, the residual stress distribution along depth was measured by X-ray diffraction (XRD) method. The residual stress distribution by experiments was agreed with the simulated results, which verified the availability of 3D finite element dynamic analysis

The potential of hematopoietic growth factors for treatment of Alzheimer's disease: a mini-review

There are no effective interventions that significantly forestall or reverse neurodegeneration and cognitive decline in Alzheimer's disease. In the past decade, the generation of new neurons has been recognized to continue throughout adult life in the brain's neurogenic zones. A major challenge has been to find ways to harness the potential of the brain's own neural stem cells to repair or replace injured and dying neurons. The administration of hematopoietic growth factors or cytokines has been shown to promote brain repair by a number of mechanisms, including increased neurogenesis, anti-apoptosis and increased mobilization of bone marrow-derived microglia into brain. In this light, cytokine treatments may provide a new therapeutic approach for many brain disorders, including neurodegenerative diseases like Alzheimer's disease. In addition, neuronal hematopoietic growth factor receptors provide novel targets for the discovery of peptide-mimetic drugs that can forestall or reverse the pathological progression of Alzheimer's disease

Joint analysis of three genome-wide association studies of esophageal squamous cell carcinoma in Chinese populations

We conducted a joint (pooled) analysis of three genome-wide association studies (GWAS) 1-3 of esophageal squamous cell carcinoma (ESCC) in ethnic Chinese (5,337 ESCC cases and 5,787 controls) with 9,654 ESCC cases and 10,058 controls for follow-up. In a logistic regression model adjusted for age, sex, study, and two eigenvectors, two new loci achieved genome-wide significance, marked by rs7447927 at 5q31.2 (per-allele odds ratio (OR) = 0.85, 95% CI 0.82-0.88; P=7.72x10−20) and rs1642764 at 17p13.1 (per-allele OR= 0.88, 95% CI 0.85-0.91; P=3.10x10−13). rs7447927 is a synonymous single nucleotide polymorphism (SNP) in TMEM173 and rs1642764 is an intronic SNP in ATP1B2, near TP53. Furthermore, a locus in the HLA class II region at 6p21.32 (rs35597309) achieved genome-wide significance in the two populations at highest risk for ESSC (OR=1.33, 95% CI 1.22-1.46; P=1.99x10−10). Our joint analysis identified new ESCC susceptibility loci overall as well as a new locus unique to the ESCC high risk Taihang Mountain region

Surface Characteristic and Friction Behavior of Plasma Sprayed FeCoNiCrMo0.2 High Entropy Alloy Coatings on BS960 High-Strength Steel with Subsequent Shot Peening Treatment

The FeCoNiCrMo0.2 high entropy alloy coatings were deposited on BS960 high strength steel by plasma spraying method with four different current intensities (250 A, 350 A, 450 A, 550 A). These coatings were then subjected to a subsequent micro-shot peening treatment. Surface characteristics including surface morphology, microhardness and phase composition were characterized, and the wear resistance of the coatings was assessed by reciprocal friction and wear tests. The results showed that the high entropy alloy coatings had FCC structure. XRD results showed that no new phase was formed during the spraying process. At the same time, shot peening treatment could effectively improve the hardness of the coating surface. Under the four processes, the coating surface prepared with the current intensity of 350 A had the highest microhardness and uniformity before and after shot peening, and the hardness values were 473 ± 10.21 and 504 ± 8.62 HV0.2, respectively. The friction and wear test results showed that the friction coefficients of the four coatings were close to each other at 10 N load, which was about 0.4. When the test load reached 25 N, the friction coefficient of the coating with current intensity of 350 A was lower, and it showed better friction performance. After shot peening, the friction coefficient of the four coatings further decreased to about 0.3 under 10 N loading due to the existence of hardened surface layer. When the test load reached 25 N, the hardened layer would be worn through and the friction coefficient would suddenly rise. Under the 25 N test load, the hardened layer of the high-entropy alloy coating with current intensity of 350 A illustrated better friction resistance

Surface Characteristic and Friction Behavior of Plasma Sprayed FeCoNiCrMo_0.2 High Entropy Alloy Coatings on BS960 High-Strength Steel with Subsequent Shot Peening Treatment

The FeCoNiCrMo0.2 high entropy alloy coatings were deposited on BS960 high strength steel by plasma spraying method with four different current intensities (250 A, 350 A, 450 A, 550 A). These coatings were then subjected to a subsequent micro-shot peening treatment. Surface characteristics including surface morphology, microhardness and phase composition were characterized, and the wear resistance of the coatings was assessed by reciprocal friction and wear tests. The results showed that the high entropy alloy coatings had FCC structure. XRD results showed that no new phase was formed during the spraying process. At the same time, shot peening treatment could effectively improve the hardness of the coating surface. Under the four processes, the coating surface prepared with the current intensity of 350 A had the highest microhardness and uniformity before and after shot peening, and the hardness values were 473 ± 10.21 and 504 ± 8.62 HV0.2, respectively. The friction and wear test results showed that the friction coefficients of the four coatings were close to each other at 10 N load, which was about 0.4. When the test load reached 25 N, the friction coefficient of the coating with current intensity of 350 A was lower, and it showed better friction performance. After shot peening, the friction coefficient of the four coatings further decreased to about 0.3 under 10 N loading due to the existence of hardened surface layer. When the test load reached 25 N, the hardened layer would be worn through and the friction coefficient would suddenly rise. Under the 25 N test load, the hardened layer of the high-entropy alloy coating with current intensity of 350 A illustrated better friction resistance

Synergistic optimization of microstructures and properties of electrodeposited Ni–CeO2 composite coatings with CeO2 microparticles and CeO2 nanoparticles

The synergistic mechanism of microparticles and nanoparticles on optimizing microstructures homogeneity and enhancing microhardness and corrosion resistance of mixed coatings was deeply researched by co-electrodepositing CeO2 microparticles and CeO2 nanoparticles into nickel matrix. Microparticles contribute to enhancing the microhardness of the coating, while nanoparticles promote the homogeneity of the microstructure, thereby improving the corrosion resistance of the coating. Therefore, by co-electrodepositing microparticles and nanoparticles into the nickel matrix, microparticles and nanoparticles in the nickel matrix generate a synergistic optimization effect, combining the advantages of microparticles and nanoparticles. Microparticles are mainly responsible for enhancing the microhardness of the coating, while nanoparticles are responsible for promoting the homogeneity of the microstructure in the coating, maintaining a homogeneous distribution of microhardness, and improving the corrosion resistance of the coating. Ultimately, the mixed coating achieves both high microhardness and excellent corrosion resistance, along with homogeneous microhardness distribution