Showing papers by "Xinhua Wu published in 2013"
TL;DR: In this article, the authors found that the as-fabricated density of parts manufactured from Hastelloy-X by SLM could be increased from 77 to 99% by decreasing the laser scan speed, and that the degree of cracking can be reduced by decreasing minor alloying additions such as Mn and Si.
119 citations
01 Mar 2013-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a high strength high γ ′ fraction of nickel-based superalloy powder RR 1000 has been hot isotatically pressed (HIPed) at different temperatures.
Abstract: A high strength high γ ′ fraction nickel-based superalloy powder RR 1000 has been hot isotatically pressed (HIPed) at different temperatures. Microstructural analysis and assessment of the tensile properties were performed on these samples. It was found that HIP led to the formation of (Hf,Zr)O 2 particles on prior particle boundaries (PPBs) which were not present in the as-received powder. It is suggested that the oxides are formed by the diffusion of Hf and Zr from the interior of powder particles to the particle surfaces where oxygen level is usually high. When different HIP temperatures were used, no obvious effect on oxide size and distribution was observed but there was an effect on the microstructure and tensile properties. Thus, HIPing at super-solvus temperatures reduced the density of PPBs over the density observed in samples HIPed at sub-solvus temperatures by making grains within the original powder particles grow beyond the precipitates on PPBs, resulting in larger grains with serrated boundaries. Slow cooling from HIPing temperatures also led to the formation of irregular-shaped γ ′. The 0.2% yield strengths at room temperature and at 700 °C were found to decrease with increase of HIP temperature but the high temperature ultimate tensile strengths and elongation increased considerably. Increasing HIPing temperature from sub-solvus to super-solvus temperatures also led to the transition of fracture mode from interparticle debonding to transgranular fracture mode.
98 citations
TL;DR: In this article, a nickel-based superalloy powder RR1000 has been hot isostatically pressed (HIPed) and heat treated to produce different microstructures using a scanning electron microscope (SEM).
65 citations
TL;DR: In this article, the mechanical properties and microstructure of the as-deposited SC420 and of hot isostatically pressed DLF builds were investigated as a function of deposition direction and sample size using tensile testing, scanning electron microscopy and X-ray diffraction.
52 citations
20 Oct 2013
TL;DR: In this article, the influence of microstructure of cast Ti-6Al-4V large thin wall structure on fatigue crack propagation and fracture toughness was investigated, and the relationship between microstructures and fracture crack propagation was established and comparison has been made between the as-cast and post HIPped conditions.
Abstract: The study is part of research activities for EU-China FP7 collaborative project (FP7-AAT- 2010-RTD-CHINA): Casting of Large Ti Structures (COLTS) and has been carried out in order to investigate the influence of microstructure of cast Ti-6Al-4V large thin wall structure on fatigue crack propagation and fracture toughness. Some samples were post HIPped (hot isostatic pressed). The effects of grain morphology on fracture and fatigue crack propagation mechanism have also been studied. The fracture surface has been examined using scanning electron microscopy (SEM). The relationships between microstructure and fatigue crack propagation rate and fracture toughness were established and comparison has been made between the as-cast and post HIPped conditions. Keywords Ti-6Al-4V alloy, Hot isostatic pressing, Fracture toughness, Fatigue crack growth
2 citations