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With the development of rapid prototyping (RP) technology, the contradiction between fabricating speed and precision becomes more and more acute. In order to solve the contradiction, a regional effective adaptive delaminating algorithm is proposed in this paper. It is different from the traditional method that the regional adaptive delaminating method divides slicing contours into several regions and adaptively delaminates in respective region only according to the contours information. Namely, this method can not only adaptively delaminate at different height of CAD model but also adaptively delaminate different regions in one slicing layer. Furthermore, be- cause the two-dimensional contour data adopted in this method are necessary for rapid prototyping system, this regional effective adaptive delaminating method is suitable for all RP systems. A comparative study is used to analyze the effectiveness of this method, which can demonstrate that this method can increase the fabricating speed and reduce the running cost under the condition of ensuring fabricating precision. [ABSTRACT FROM AUTHOR]

• Introduced bimodal SiC powder, enhancing BJ process and powder properties. • All stages of microstructure and performance are investigated. • The flexural strength and fracture toughness increased by 42.3 % and 25.3 %. Binder jetting (BJ) additive manufacturing has emerged as a promising technique for batch production of complex silicon carbide (SiC) ceramic components. However, the utilization of coarse powder in BJ often leads to lower density and strength in green parts and final composites compared to conventional fabrication methods. This study aims to enhance the mechanical performance of SiC ceramics through a novel bimodal SiC powder formulation for BJ, complemented by phenolic resin impregnation and pyrolysis (PRIP) and liquid silicon infiltration (LSI). The optimal ratio of bimodal powder, comprising 75 % coarse and 25 % fine powder, was determined through a comprehensive analysis of the microstructure and properties at various stages of the preparation process. The bimodal powder achieves a packing density of 48.3 % and exhibits satisfactory flowability. Notably, the density of the green part reaches 1.78 g/cm3, which is 31 % and 4.7 % higher than that of unimodal fine and coarse powders, respectively. Following the LSI process, the final Si-SiC composites display a high flexural strength of 276.6 ± 13.3 MPa and fracture toughness of 3.52 ± 0.12 MPa·m1/2. These values represent increases of 42.4 % and 25.3 %, respectively, compared to the composites derived from unimodal coarse powder. The material compositions and fabrication strategies proposed in this work offer an effective pathway for creating high-performance SiC ceramic composites via binder jetting. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract With the aim of improving the strength and ductility of TiAl alloy, for the first time, nano-WC is introduced to reinforce the Ti-44.5Al-5Nb-0.5W-0.5C-0.2B through hot isostatic pressing (HIP). The effect of nano-WC contents on the microstructures and mechanical properties of Ti-44.5Al-5Nb-0.5W-0.5C-0.2B are systematically studied, specifically, the Ti-44.5Al-5Nb-0.5W-0.5C-0.2B alloy with 2 wt% nano-WC content shows the highest tensile strength (830 ± 33 MPa) and ductility (3.9 ± 0.2%), which are mainly attributed to the grain refinement strengthening and precipitate shearing strengthening effects. Our findings provide a realistic approach to design novel TiAl/WC nanocomposite processed by HIP with superior strength-ductility combination for practical structural applications. Graphical abstract Image 1 Highlights • The nano-WC reinforcement is uniformly distributed in the TiAl matrix. • The average grain size is generally refined with the increase of nano-WC content. • The phase evolution mechanism of TiAl/WC nanocomposite is discussed in detail. • The TiAl/WC parts exhibit high strength and strain than traditional counterparts. [ABSTRACT FROM AUTHOR]

The microstructures and compressive properties of Ti-46.5Al-2.5Cr-2Nb-0.5Y alloy with varied boron (B) addition processed by selective laser melting (SLM) had been systematic studied. With increasing the B content from 0 to 2 wt%, the average grain size of SLM-processed Ti-46.5Al-2.5Cr-2Nb-0.5Y/B composites decreased from 16.64 µm to 5.66 µm, meanwhile, the {0001} texture index and high angle grain boundaries (HAGBs) increased from 10.78 and 87.9% to 22.69 and 94.4%. The phase evolution mechanism of Ti-46.5Al-2.5Cr-2Nb-0.5Y/B composites during the SLM process can be summarized as: firstly, β and B phases precipitated out from the liquid phase, then the β phase transformed to α phase and part of the α phase transferred to γ phase, later, some new phases of TiB 2 and AlB 2 emerged by the diffusion mechanism of B, Ti and Al atoms, and then the β and α phases orderly transformed to B 2 and α 2 , lastly, the γ, B 2 , B, TiB 2 , AlB 2 phases in a range of several hundred nanometers were randomly distributed within the α 2 matrix. Due to the grain refinement strengthening mechanism, the compressive strength and strain of Ti-46.5Al-2.5Cr-2Nb-0.5Y/B parts increased to the maximum of 1610.53 MPa and 5.17%. [ABSTRACT FROM AUTHOR]

One of the first attempts on fabricating functionally graded materials (FGMs) of titanium/hydroxyapatite (Ti/HA) with quasi-continuous ratios by selective laser melting (SLM) was done. HA ratios varied among the layers of FGMs from 0 wt% to 5 wt% with 1 wt% gradient. The 3D reconstruction of Ti/HA FGM bulk with micro-pores was presented through micro-CT, and the percentage of micro-pore increased from 0.01% to 3.18% with the increasing of HA ratio. The scanning electronic microscope results showed that the crack was positively correlated to HA ratio with the crack density increasing from 1.5 × 10 − 4 μm/μm 2 to 2.7 × 10 − 3 μm/μm 2 . The microstructure evolution from 0% to 5% HA ratios could be elucidated as long lath-shaped grains → long acicular-shaped grains → short acicular-shaped grains → continuous circle-shaped grains → quasi-continuous circle-shaped grains, due to the perturbation in the melting pool and obstruction of crystal development by HA. Accordingly, the FGM provides a wide range of nanohardness from 5.11 to 8.36 GPa and Vickers hardness from 3.42 to 5.67 GPa. Moreover, the fracture toughness from 2% to 5% HA ratios ranges from 3.41 MPa m 1/2 to 0.88 MPa m 1/2 , which can be tailored to fit that of cortical and cancellous bones. [ABSTRACT FROM AUTHOR]

The microstructure design strategy is introduced to improve the mechanical property of a novel γ-Ti-43.5Al-6.5Nb-1.5Cr-0.5C/TiB 2 metal matrix composite (MMC) fabricated by hot isostatic press (HIP). With increasing the content of TiB 2 from 0 to 3 wt%, the average grain size, {001} maximum texture index and average schmid factor of HIP-processed Ti-43.5Al-6.5Nb-1.5Cr-0.5C/TiB 2 parts generally decrease from 27.4 μm, 7.9 and 0.43 to 22.7 μm, 4.1 and 0.38, in addition, the crystallographic texture transforms from the mixture of (001) and (111) orientations to a strong (101) orientation. The phases evolution mechanism in the HIP-processed Ti-43.5Al-6.5Nb-1.5Cr-0.5C/TiB 2 parts can be divided into four steps: first of all, β phase transforms to γ and α phases, then, a small amount of new phases of TiB and TiC emerge by the diffusion of Ti and C atoms, subsequently, the β and α orderly transform to B 2 and α 2 , lastly, the B 2 , α 2 , TiB 2 , TiB and TiC uniformly distribute in the γ matrix. Both the tensile strength and strain of HIP-processed Ti-43.5Al-6.5Nb-1.5Cr-0.5C/TiB 2 components increase from 471.9 MPa and 1.7% to 653.4 MPa 2.1% with the increase of TiB 2 content from 0 to 3 wt%. [ABSTRACT FROM AUTHOR]

• A self-developed binder with A-stage phenolic resin as a key agent was prepared. • High strength 316 L green part with low binder saturation was fabricated by BJAM. • The uneven distribution of binder hinders the strength of green parts. Recently, binder jetting additive manufacturing (BJAM) was used to manufacture complex metal parts in an economical and large-scale way. However, the usage of resin to bond metal powder renders as-printed green parts with low strength, which is potential to cause the structural damages of final parts during post treatments. To overcome the intractable problem, a self-developed binder mainly consisting of A-stage phenolic resin was explored for BJAM to achieve relatively high-strength as-printed green parts. The binder can be cured as a C-stage phenolic resin with 190 ℃ and then provide a high strength for the green parts. The effect of layer thickness and binder saturation on the strength, dimensional accuracy, and surface roughness of the BJAM-printed 316 L stainless-steel green samples using the developed binder was investigated systematically. With the optimized parameters (a layer thickness of 100 μm and a binder saturation of 30.2 %), green samples can possess the ultimate bending strength (UBS) of 10.08 MPa and the ultimate compressive strength (UCS) of 25.56 MPa, which are beneficial for the structural stability of the printed samples during subsequent treatments. A reduction in strength and an increase in roughness are observed with increasing the layer thickness for the as-printed green samples. An increment in binder saturation results in the improvement in strength and surface roughness of the green samples. The relationships between the binder and the mechanical performance of the green samples were discussed from the viewpoint of the uneven distribution of binder in depth. This work explored a promising binder with a low saturation for BJAM to fabricate 316 L green parts with desirable mechanical strength and acceptable surface roughness. [ABSTRACT FROM AUTHOR]