新型Al/CuFe多层核壳颗粒增强铝基复合材料的显微组织和力学性能

采用不同烧结工艺制备新型Al/Cu Fe多层核壳颗粒增强铝基复合材料(AMCs),研究其对显微组织和力学性能的影响。分别采用电置换法和化学镀法在铝粉颗粒上沉积Cu层和Fe层,制备多层Al/Cu Fe核壳颗粒。采用X射线衍射(XRD)、扫描电子显微镜(SEM)/能谱(EDX)、密度计、显微硬度和压缩试验等方法对复合材料进行表征。结果表明,在放电等离子烧结复合材料中,由于沉积层向金属间化合物相转变,界面反应程度提高,复合材料的相对密度(99.26%)、显微硬度(165 HV0.3)和强度(572 MPa)均显著提高。此外,热压复合材料壳层结构中存在的未转化Cu导致其断裂应变最高(20.4%)。研究结果对通过选择合适的烧结路径来调整AMCs的显微组织和控制其力学性能具有重要意义。

Influence of particulate morphology on microstructure and tribological properties of cold sprayed A380/Al2O3 composite coatings

In this study,three kinds of A380/Al2O3 composite coatings were prepared by cold spray(CS)using spherical,irregular and spherical+irregular shaped Al2O3 particulates separately mixed in the original A380 alloy powders.The influence of Al2O3 particulates’morphology on the microstructural characteristics(i.e.retention of Al2O3 content in coatings,coating/matrix interfacial bonding,pore size distribution and morphology etc.)and wear performance of the coatings was investigated by scanning electron microscopy(SEM),X-ray computed tomography(XCT)and 3-D optical profilometry.Results indicated that the spherical Al2O3 showsobvious tamping effect during deposition process.As a result,the interfaceshowedawavy shape while the matrix and particulates were mechanical interlocked with much improved adhesion.In addition,the porosity of the coating was minimized and the pores exhibited curved spherical structure with reduced dimensions.The irregular Al2O3 particles predominantly displayed the embedding effect together with fragmentation of Al2O3 particulates.Consequently,poor coating/matrix interfacial bonding,high porosity and the formation of angular-shaped pores were resulted in the coating.Dry sliding wear tests results revealed that the wear resistance of the coating is directly related with the retained content of Al2O3 in the coating.The coating containing irregular Al2O3 particulates displayed superior wear performance with its wear rate one seventh of that of the pure A380 alloy coating.The coating containing both kinds of Al2O3 particulates showed mixed characteristics of above two kinds of Al2O3 composite coatings.

Effects of Dissimilar Alumina Particulates on Microstructure and Properties of Cold-Sprayed Alumina/A380 Composite Coatings

In this study,alumina/A380 composite coatings were fabricated by cold spray.The influence of alumina particulates,morphology(spherical and irregular)and content on the deposition behavior of the coatings(including surface roughness,surface residual stress,cross-sectional microstructure and microhardness)was investigated.Results revealed that the spherical alumina mainly shows micro-tamping effect during deposition,which result in remarkable low surface roughness and porosity of the coatings.In addition,very low deposition efficiency and good interfacial bonding between the coating and the substrate were achieved.For irregular alumina particles,the embedding of ceramic particulates in the coating was dominant during deposition process,resulting in high retention in the final deposit.However,it showed limited influence on porosity,surface roughness and interfacial bonding of the deposit.The coatings containing irregular alumina particulates exhibited much higher microhardness than those containing spherical alumina due to the higher load-bearing capacity of deposited alumina.

Erratum to “Influence of particulate morphology on microstructure and tribological properties of cold sprayed A380/Al_(2)O_(3) composite coatings” [J. Mater. Sci. Technol. 44 (2020) 9-18]

In our recently published article,“Influence of particulate morphology on microstructure and tribological properties of cold sprayed A380/Al_(2)O_(3) composite coatings”[Journal of Materials Science&Technology 44(2020)9-18]”,Fig.5 got repeated inadvertently.This led to the displacement in the order of Figs.6 and 7 one step ahead.Consequently,the captions in Figs.6-8 in the manuscript were mismatched.Further,it caused the omission of Fig.8 described in the original manuscript.This erratum corrects the order of Figs.6-8 along with their corresponding figure captions.This erratum does not affect the conclusions of that paper.The publisher would like to apologize for any inconvenience caused.

Achieving strength-ductility synergy in cold spray additively manufactured Al/B4C composites through a hybrid post-deposition treatment

Cold spray additive manufacturing(CSAM) provides a potential solid state manufacturing route to fabricate variety of aluminum matrix composites(AMCs) with reduced possibility of undesired chemical reactions and residual thermal stresses. This study presents a hybrid(i.e. hot compression + hot rolling)post-deposition treatment to reinvigorate the mechanical properties of cold spray additively manufactured Al/B4 C composites. The as-deposited samples were initially subjected to 30% thickness reduction via hot compression treatment at 500°C followed by a hot rolling treatment with 40% thickness reduction in 2 passes. Electron backscatter diffraction(EBSD) and high resolution transmission electron microscopy(HRTEM) results revealed that after hybrid post-deposition treatment(involving 70%accumulative thickness reduction), the aluminum grains in the matrix were extensively refined due to simultaneous operation of continuous dynamic recrystallization(CDRX) and geometric dynamic recrystallization(GDRX). Furthermore, interfacial defects were remarkably reduced while the nature of Al/Al and Al/B4C interfacial bonding was changed from sheer mechanical interlocking to metallurgical bonding which facilitated efficient transference of applied load to uniformly dispersed bimodal B4C particles. As a result, ultimate tensile strength(UTS) and elongation(EL) of the as-deposited sample were simultaneously improved from 37 to 185 MPa and 0.3% to 6.2%, respectively.

Effect of strain rate on plastic deformation bonding behavior of Ni-based superalloys

Plastic deformation bonding(PDB)has emerged as a promising solid state bonding technique with limited risk of phase transformations and residual thermal stresses in the joint.In this study,the PDB behavior of IN718 superalloy was systematically investigated by performing a series of isothermal compression tests at various processing conditions.It was revealed that,with increasing PDB strain rate at 1000?C,different extents of dynamic recrystallization(DRX)occur in the bonding area of IN718 joints.The extent of DRX,average size of DRXed grains,and a newly proposed"interfacial bonding ratio(?Bonding)"parameter(to quantify the bond quality)were initially reduced with increase in the strain rate up to 0.1 s-1 and later increased at further higher strain rates.Electron backscattered diffraction(EBSD)and transmission electron microscopy(TEM)based interfacial microstructure analyses indicated that the quality of the bonded joints is closely related with the development of fine DRXed grains at the bonding interface with the increasing strain,which promotes adiabatic temperature rise.It was revealed that the initial bulging and subsequent migration of the original interfacial grain boundary(IGB)were the main mechanisms promoting DRX in the well bonded IN718 superalloy joints.Moreover,the mechanical properties of the bonded joints were not only controlled by the recrystallized microstructure but also depended upon the Bonding parameter of the joints.

Microstructure and Mechanical Properties of Ti–Ta Composites Prepared Through Cold Spray Additive Manufacturing

In this study, an innovative approach was used to fabricate Ti–Ta composite biomaterials through cold spray additive manufacturing followed by a diff usion treatment. The microstructure and mechanical properties of the composites were investigated in detail using field emission scanning electron microscopy, electron backscatter diff raction, 3D X-ray computed tomography, tensile test, nanohardness test and resonance vibration test. The obtained results indicated that the prepared composites have inhomogeneity in their microstructure and composition. A unique microstructure, composed of Ti-rich, Ta-rich and diff usion regions, was evolved in the composites due to incomplete diff usion between Ti and Ta splats. Further, Kirkendall pores were formed in the composites due to uneven diff usion of the two phases(of Ti and Ta) during high-temperature heat treatment. The prepared composites simultaneously showed low elastic modulus and high tensile strength which is required for a good biomaterial. Low elastic modulus was associated with the residual pores and the alloying eff ect of Ta in Ti, while high tensile strength was related to the solid solution strengthening eff ects. The obtained results indicated that the prepared Ti–Ta composites have a great potential to become a new candidate for biomedical applications.

A viable approach to repair neutron shielding B_(4)C/6061 Al composite sheets through cold spray and hot rolling co-treatment

Cold spray(CS) is considered as a new type of repairing technique for restoration or remanufacturing of a wide range of unserviceable engineering components due to its unique ‘cold’ characteristic. In this work, a viable repairing approach i.e. "cold spraying followed by hot rolling post-treatment" was successfully applied to restore defective neutron shielding B_(4)C/6061 Al composite plates. Scanning electron microscopy(SEM) and electron backscatter diffraction(EBSD) results revealed that the coating-substrate interface is in a good bonding state without micro-cracks. Hot rolling post-treatment resulted in improved microstructure of the as-sprayed deposit with more uniform distribution of B_(4)C particles in the matrix.Moreover, well bonded splat boundaries and strain free Al grains were evolved in the matrix due to enhanced splat deformation and continuous dynamic recrystallization(CDRX). Three-point bending test results revealed that the strength of the repaired material is at par with the in-service plates. The findings of this work could be considered as a great stride to further extend possible applications of CS for repairing engineering structural components.