Explore the vast range of titles available.

This study investigates the effect of hot isostatic pressing (HIPping) on the static and fatigue properties of sand-casting A356 aluminium alloys. HIPping is a method to improve the fatigue properties in aluminium cast material by reducing or eliminating the inner porosities. Investigation of the complex interaction between the microstructural features on mechanical properties before and after the HIPping process was examined using computed tomography and scanning electron microscopy (SEM). Castings generally contain pores and defects that have a detrimental impact on the fatigue properties. The HIPping process closes the porosities in all investigated samples with an increase in density. Without significant defects, the mechanical performance improved in the finer microstructure. However, a considerable variation in the results was found between the different conditions, whereas the coarser microstructure with larger porosities before HIPping showed remarkably reduced results. The high-cycle fatigue-tested samples showed reduced fatigue propagation zone in the coarser microstructure. Moreover, large cleavage areas containing bifilms in the fracture surfaces indicate that the healing process of porosities is inefficient. These porosities are closed but not healed, resulting in a detrimental effect on the static and dynamic properties.

Materials needed to achieve designed performance will require formulations and processing methods capable of delivering a compendium of metallic, ceramic and cermet chemistries, which must be finely tuned at source, and tolerant to down-stream thermomechanical adjustment. Structural steels and cermets are continuously being developed by researchers using computational thermodynamics modelling and modified thermomechanical treatments, with oxide dispersion strengthened steel (ODS)-reduced activated ferritic-martensitic steel (RAFM) steels based on 8%–16% wt.% Cr now being assessed. The combination of SiC f and CuCrZr as a metal matrix composite containing an active coolant would be seen as a major opportunity, furthermore, composite ceramic materials consisting of SiC fibres reinforcing a SiC matrix capable of being joined to metallic structures offer great potential in the development of advanced heat exchangers. Continuing the theme of advanced manufacturing, the use of solid-state processing technologies involving powder metallurgy–hot isostatic pressing and spark plasma sintering to produce near-net shaped products in metallics, ceramics and cermets are critical manufacturing research themes. Additive manufacturing (AM) to produce metallic and ceramic components is now becoming a feasible manufacturing route, and through the combination of AM and subtractive machining, capability exists to produce efficient fluid carrying structures that could not be manufactured by any other process. Extending this to using electron beam welding and advanced heat treatments to improve homogeneity and provide modularity, a two-pronged solution is now available to improve capability and integrity, whilst concurrently offering increased degrees of freedom for designers.

Fine grained 8 mol% yttria-stabilized zirconia (8YSZ) transparent ceramics with high optical and mechanical properties were fabricated by air pre-sintering and hot isostatic pressing (HIP) using commercial 8YSZ powders as the raw material. The pre-sintered ceramics with fine grains and appropriate relative density play a key role to achieve high transparency and suppressed grain size after HIP post-treatment at relatively low temperatures. With the increase of HIP temperature from 1350 to 1550 °C, the in-line transmittance of 8YSZ ceramics at 600 nm increases from 56.9% to 71.5% (2.5 mm in thickness), and the average grain size increases from 2.4 to 16.3 µm. The corresponding bending strength of 8YSZ transparent ceramics decreases from 328±20 to 289±19 MPa, the hardness ( H ) decreases from 12.9±0.1 to 12.5±0.2 GPa, and the fracture toughness ( K IC ) decreases from 1.30±0.02 to 1.26±0.03 MPa·m 1/2 . Systematical investigations were carried out to study the combination of high optical transparency and excellent mechanical properties in 8YSZ ceramics.

Nickel-based GH3536 alloys prepared by laser powder bed fusion (LPBF) exhibit a mismatch between strength and ductility during the tensile process, which severely restricts their engineering applications in the aerospace field. In order to optimize their performance, this study adopted hot isostatic pressing (HIP) and subsequent heat treatment (HT) to modify the material. The microstructural evolution of the HIP+HT-treated GH3536 alloy during deformation, including grain rotation, grain boundary migration, and dislocation slip transfer behaviors, was systematically investigated at room temperature using in situ tensile experiments. The relationship between the microstructure and mechanical properties was elucidated in greater depth by combining theoretical calculations. The experimental results show that after HIP+HT treatment, the elongation of the alloy increased significantly from 36.5% in the as-built LPBF condition to 45.3 ± 1.6% without a significant reduction in ultimate tensile strength. The plasticity enhancement is mainly attributed to the elimination of defects and the formation of annealing twins. In addition, the formation of substructures inside the grains also delays the fracture of the specimen to some extent. This study is expected to provide a reference for the subsequent optimization of the mechanical properties of alloys via heat treatment processes.

The density of SLMed (Selective Laser Melting) Ti-22Al-25Nb alloy was improved through hot isostatic pressing (HIP) treatment, and the influence of HIP and solution aging on the microstructure of Ti-22Al-25Nb alloy in the as-deposited state was examined. The results indicate that following (1100 °C + 300 MPa)/3 h-HIP, the specimen densities have risen to 99.71%, porosity has markedly decreased, and internal flaws have been eradicated. Microstructural analysis reveals a significant presence of GBα2 (GB, Grain Boundary) along grain boundaries, with GBLO + α2 (GBL, Grain Boundary Lath; O, Orthorhombic) laths extending parallel from the grain boundaries into the intragranular region. Additionally, a limited number of cross or snowflake O + α2 lath clusters and acicular O phases are precipitated within the B2 (B, Body-centered cubic) phase in the HIPed state, characterized by isotropic and linear grain boundaries. The GBLα2 and GBLO exhibit two growth modes: sympathetic nucleation and interfacially unstable nucleation. During the solid solution treatment following HIP, as the solid solution temperature rises, the acicular O phase, GBLO, lath O phase, lath α2, and GBα2 sequentially dissolve, increasing the volume fraction of the B2 phase. After HIP, the aging microstructure is primarily characterized by the proliferation of the acicular O phase precipitated from the B2 phase and retaining the lath O phase in a solid solution. The precipitation of GBLO in the original solid solution is suppressed, and the GBLα2 in the original solid solution partially decomposes into rimO, resulting in coarse grain size and significant internal decomposition of α2. Following solution treatment and aging at 920 °C, the proliferation of the acicular O phase enhances ductility, resulting in ideal overall characteristics with a yield strength (YS) of 760.81 MPa, ultimate tensile strength (UTS) of 869.32 MPa, and elongation (EL) of 2.683%. This study demonstrates that the HIP treatment and the modification of solution aging parameters can substantially increase the density and refine the microstructure of Ti-22Al-25Nb alloy, hence enhancing its mechanical properties.

316L stainless steel is widely employed in various industrial sectors, including shipbuilding, offshore plants, high-temperature/high-pressure (HTHP) piping systems, and hydrogen infrastructure, due to its excellent mechanical stability, superior corrosion resistance, and robust resistance to hydrogen embrittlement. This study presents 316L stainless steel alloys fabricated via hot isostatic pressing (HIP), conducted at 1300 °C and 100 MPa for 2 h, incorporating Cr2N powder and an optimized Ni/Mn ratio based on the nickel equivalent (Ni_eq). During HIP, Cr2N decomposition yielded a uniformly refined, dense austenitic microstructure, with enhanced corrosion resistance and mechanical performance. Corrosion resistance was evaluated by potentiodynamic polarization in 3.5 wt.% NaCl after 1 h of OCP stabilization, using a scan range of −0.25 V to +1.5 V (Ag/AgCl) at 1 mV/s. Optimization of the Ni/Mn ratio effectively improved the pitting corrosion resistance and mechanical strength. It is cost-effective to partially substitute Ni with Mn. Of the various alloys, C13Ni-N exhibited significantly enhanced hardness (~30% increase from 158.3 to 206.2 HV) attributable to nitrogen-induced solid solution strengthening. E11Ni-HM exhibited the highest pitting corrosion resistance given the superior PREN value (31.36). In summary, the incorporation of Cr2N and adjustment of the Ni/Mn ratio effectively improved the performance of 316L stainless steel alloys. Notably, alloy E11Ni-HM demonstrated a low corrosion current density of 0.131 μA/cm2, indicating superior corrosion resistance. These findings offer valuable insights for developing cost-efficient, mechanically robust corrosion-resistant materials for hydrogen-related applications. Further research will evaluate alloy resistance to hydrogen embrittlement and investigate long-term material stability.

This paper reports the effect of hot isostatic pressing (HIP) on the porosity, microstructure and mechanical properties of laser powder bed fusion (LPBF) IN625 structures built at a higher layer thickness of 100 µm. It is observed that the process-induced pores/voids of volume fraction ( V f ) 0.43% in as-built IN625 structures are reduced significantly to ~ 0.01% after HIP treatment. The microstructure is changed from fine columnar dendrites to coarse equiaxed dendrites. The microstructural analysis of as-built structures reveals the presence of cellular/dendritic growth along with elemental segregation of Nb, Si and C and precipitation of Nb-rich carbides, whereas coarse recrystallized microstructure along with elemental segregation of Si and precipitation of Nb, Mo and Cr rich carbides is observed in hot isostatic pressed (HIP) samples. HIP structures exhibit lower tensile strength, higher ductility and lower anisotropy as compared to LPBF built structures. There is a reduction in the Vickers micro-hardness of IN625 samples after HIP, and the values are observed to be similar to their conventional counterparts. Further, an increase in the energy storage capacity of the material is observed after HIP treatment through Automated Ball Indentation (ABI ® ) studies. The study paves a way to develop ~ 100% dense, defect-free and isotropic engineering components using LPBF.

1.2C–4Cr–4Mo–10W–3.5V–10Co–Fe high-speed steel (JIS SKH57; ISO HS10-4-3-10) is often manufactured via casting and forging. By applying powder metallurgy, the properties of the abovementioned material can be improved. In this study, the effects of sintering conditions on the formation of precipitates and pores are evaluated. Additionally, strength with and without hydrostatic pressure during sintering is evaluated via static bending and impact tests. Sintering via hot isostatic pressing (HIP) at 1463 K can effectively eliminate pores and prevent the coarsening of precipitates. Toughness and strength improved by 50% by applying HIP.

A reliable bonding interface between steel and Ti alloy is required for producing a steel/Ti bimetal composite. In this study, molecular dynamic simulations and diffusion welding experiments using the hot isostatic pressing process were conducted to study the atomic diffusion at the Fe-Ti interface. The simulation results indicate that the diffusion layer thickness is thinner in single crystals compared to polycrystals at the same temperature. This difference may be explained by polycrystals having grain boundaries, which increase atomic disorder and facilitate diffusion. The radial distribution function (RDF) curves for Fe-Fe and Ti-Ti exhibit a similar pattern over time, with a main peak indicating the highest atom density within a specific radius range and relatively strong binding between the central atoms and their nearest neighbors. The observed changes in the diffusion coefficient with temperature in the simulations align well with the experimental results. This study enhances the understanding of Fe-Ti interface diffusion mechanism and provides valuable insights for broader applications of steel/Ti bimetal composites.

Cobalt leaching resistance of the solidified radioactive sludge subject to disposal was evaluated. The sludge powders ((Fe 2 O 3 ), NiO, and Cr 2 O 3 ) with non-radioactive cobalt powder was homogeneously mixed with ferro frit and treated in hot isostatic pressing process. Although the mixing ratio of the ferro frit in total solidified sludge waste was less than 25% and heating temperature in HIP process was lower than 1000 °C, the cobalt leachability indices in all the solidified sludge were ranged from 13.9 to 18.4. The study showed the solidified sludge waste satisfied the leachability index criteria for waste disposal, which was six.