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Highlights • AAFs have been additive manufactured by LMD process. • Ni-TiH 2 has good foaming ability during LMD process. • The AAFs possess different porosity and pore-size with different Ni-TiH 2 addition. • Sound-insulated capability of AAF can be changed by regulating LMD process. Abstract Compared with traditional preparation methods to fabricate aluminum foams, additive manufacturing technology have some advantages such as the ability to prepare complex shapes and relatively high processing efficiency. In this paper, laser melting deposition (LMD) process has been used to additive manufacture aluminum alloy foams (AAFs). During LMD process, Ni-coated TiH 2 was used as the foaming agent. AAFs with different porosity and pore-size have been manufactured by LMD process. The pore size and porosity of AAFs are increasing with increasing addition of Ni-TiH 2. The sound insulation measurement results indicate that porosity and pore-size have influence on sound-insulated capability. With pore size and porosity increasing, sound-insulated capability of AAFs show a trend of decreasing at first and increasing later. [ABSTRACT FROM AUTHOR]

Underwater laser repairing technology as a new type of on-line maintenance technology will promote the development of oceanographic engineering. However, there are many difficulties during the process of underwater laser repairing. In this paper, underwater laser cladding process in full wet surroundings (or WULC, for short) for fabrication of nickel aluminum bronze (or NAB, for short) has been reported, and laser cladding process in the air for fabricating NAB coatings was used for comparative study. The homemade protective covering was used to solve the problems of underwater laser repairing. For comprehending the effect of full wet surroundings and protective covering on microstructure and electrochemical performance of the NAB coatings, a series of characterization tests including SEM, EDS, XRD and TEM and a series of electrochemical measurements were carried out. The alloy coatings fabricated by WULC possess good formability through optimizing the processing parameters. The elements distribution of the coatings shows different patterns compared to conventional cast copper alloy and NAB coating fabricated by laser cladding in the air. In addition, the ordered solid solution and twinning structure have been observed in the WULC-NAB coatings. These unique microstructures and elements distribution patterns caused the better electrochemical performance of NAB coating fabricated by WULC. These findings suggest that the idea of using a protective layer in underwater laser cladding in full wet surroundings is feasible. The WULC process reported in this paper can provide some theoretical guidance for repairing damaged parts in full wet surroundings. [ABSTRACT FROM AUTHOR]

Abstract Laser additive manufacturing is an ideal choice to fabricate metal parts with complicated geometric shapes. In this research, (Fe 60 Co 35 Ni 5) 73.5 Si 13.5 B 9 CuMo 3 magnetic alloys with good saturation magnetization and mechanical properties were prepared by laser additive manufacturing and laser remelting. The influence of laser remelting on the hysteresis loop, microhardness, microstructure, and wear resistance of a single layer was investigated. It is found that laser remelting has a beneficial effect on the magnetic and mechanical properties. The microstructure of the remelted alloys is mainly composed of dense and homogeneous dendrites. The alloys are dominated by body-centered cubic microstructures. After laser remelting, the alloys exhibit higher saturation magnetization (165.5 emu/g) and lower coercivity (12 Oe). In addition, with the reduction of grain size, the wear resistance and microhardness of the alloys increase significantly. Highlights • A soft magnetic alloy is optimized by laser additive manufacturing. • Laser remelting has a beneficial effect on the magnetic and mechanical properties. • After laser remelting, the alloys exhibit higher saturation magnetization and lower coercivity. • Composition-microstructure-magnetic property relationships are provided. [ABSTRACT FROM AUTHOR]

Highlights • Protective material assisted underwater wet laser cladding was proposed. • The promotion mechanism of protective material is studied in detail. • The 316L coatings without obvious defects were successfully prepared underwater. • The performance of 316L coatings was improved by using protective materials. Abstract In this paper, a new underwater processing technology was proposed, called underwater wet laser cladding (UWLC). Protective material assisted UWLC was provided to increase the processed water depth of UWLC and promote the quality of UWLC coatings without changing the laser power. For comparison, the direct UWLC and protective material assisted UWLC were performed under various water depths with uniform experimental parameters. The UWLC processes under water depth of 15 mm were studied in detail. The blue-purple plasma appears during the direct UWLC processes leading to the failure of UWLC. The mental plume appears during the protective material assisted UWLC processes. In addition, the protective material assisted UWLC is more likely to succeed by increasing the content of protective material. The 316L stainless steel coatings were successfully prepared by protective material assisted UWLC. The microstructure of the 316L coatings by protective material assisted UWLC is well in agreement with 316L coatings prepared by laser cladding in air, while the 316L coating by direct UWLC is mainly composed of columnar dendrites. Moreover, the corrosion resistance of 316L coating by direct UWLC in 3.5 wt.% NaCl solutions is improved markedly by applying protective material. The energy loss in the process of underwater wet laser processing is significantly reduced through the protective material assisted method, which provides meaningful theoretical support for underwater wet laser repair. [ABSTRACT FROM AUTHOR]

Abstract In order to obtain metallurgical shape memory alloy with a better quality, electro-magnetic stirring (EMS) technology is selected as an aiding method during plasma arc deposition (PAD) process. In this work, Ti 51 Ni 49 alloys were successfully produced by EMS-assisted PAD technology. Influence of EMS on the microstructure, phase transformation behavior, micro-hardness and wear resistance of PAD TiNi alloy have been systematically investigated. The PAD TiNi alloy is composed of TiNi coarse columnar dendrites with a certain number of Ti 2 Ni phases distributed in the inter-dendritic regions. Under the action of EMS, TiNi coarse columnar dendrites transform into fine non-dendrites or spheroid grains and the homogeneity of microstructures improves significantly. The implementation of EMS during PAD do not change the path of phase transformation, but improve the degree of phase transformations and reduce the transformation temperatures of PAD TiNi alloy. The EMS-PAD TiNi alloy possesses better dry wear resistance than the PAD TiNi alloy, which can be attributed to the higher degree of pseudo-elasticity of TiNi phases and strengthening of Ti 2 Ni phases. Highlights • Ti 51 Ni 49 shape memory alloys were successfully produced by electromagnetic stirring (EMS) - assisted plasma arc deposition (PAD) technology. • Under the action of EMS, TiNi coarse columnar dendrites transform into fine non-dendrites and its homogeneity improves significantly. • The EMS-PAD TiNi alloy possesses better dry wear resistance than the PAD TiNi alloy due to the higher degree of pseudo-elasticity and strengthening of Ti 2 Ni phases. [ABSTRACT FROM AUTHOR]

La ion pre-implantation was successfully used to obtain vacuum carburized layer with ultrafine microstructure and higher case depth of AISI 9310 alloy steel. The effect of La ion pre-implantation on microstructure, case depth and hardness of carburized layer was investigated in detail. The results showed that the La 2 O 3 , BCC structure solution of La and lattice defects were introduced into AISI 9310 alloy steel by La pre-implantation. Meanwhile, the pre-implantation can effectively refine microstructure and dramatically improve diffusion coefficient of carbon and hardness of carburized layer. The La 2 O 3 and LaC 2 in situ produced during carburizing can act as potential heterogeneous nucleation sites for γ -Fe phase to refine grain. The higher carbon concentration gradient caused by the inhibition effect of La on C–C bond formation and induction of Cottrell can increase the amount of carbides in carburized layer. The excellent microstructure and higher carbon concentration gradient can enhance short-circuit diffusion to accelerate the carbon diffusion coefficient inducing the increase of hardness of carburized layer. • Carburized layer with ultrafine microstructure and higher hardness was obtained by La pre-implantation. • The carbon concentration gradient and short-circuit diffusion are enhanced by La pre-implantation during carburizing. • The La 2 O 3 and LaC 2 can act as potential heterogeneous nucleation sites for γ-Fe phase during carburizing. [ABSTRACT FROM AUTHOR]

Graphene (Gr) has been regarded as the promising reinforcement for metal matrix composite coatings. However, it is hard to mix nano-scale Gr with micron-scale metal powders effectively at present, restricting the extensive application of Gr in engineering field. Therefore, this work proposed a new two-step method to in-situ synthesize multilayer Gr on the surface of Ni60 powders by combining ultrasonic and wet milling. Under protective atmosphere, Ni60 + Gr coatings were fabricated using laser cladding technique. In-situ synthesized multilayer Gr were successfully incorporated into Ni60 coatings, but part of them were transformed into the fullerene-like structures. In addition, a new matrix phase of Ni-Cr-Fe with bcc structure was generated in Ni60 + Gr coatings owing to the super adsorption effect of Gr on Ni, Cr and Fe atoms. The second phases such as chromium carbides in Ni60 + Gr coatings were refined and distributed more uniformly compared with that of Ni60 coatings. Furthermore, Ni60 + Gr coatings showed excellent tribological performance than that of Ni60 coatings, which was attributed to the synergistic effect between the lubrication of Gr or fullerene-like structures and the superior dispersion strengthening of the second phases. • Multilayer Gr on the surface of Ni60 powders by combing ultrasonic and wet milling was in-situ synthesized. • Multilayer Gr were incorporated into Ni60 coatings, but part of them were transformed into the fullerene-like structures. • Ni-Cr-Fe with bcc structure was generated in Ni60+Gr coatings. • The second phases in Ni60+Gr coatings were refined and distributed more uniformly compared with that of Ni60 coatings. [ABSTRACT FROM AUTHOR]