Browsing by Author "Liu, Q"
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- ItemDeep surface rolling for fatigue life enhancement of laser clad aircraft aluminium alloy(Elsevier, 2014-11-30) Zhuang, W; Liu, Q; Djugum, R; Sharp, PK; Paradowska, AMDeep surface rolling can introduce deep compressive residual stresses into the surface of aircraft metallic structure to extend its fatigue life. To develop cost-effective aircraft structural repair technologies such as laser cladding, deep surface rolling was considered as an advanced post-repair surface enhancement technology. In this study, aluminium alloy 7075-T651 specimens with a blend-out region were first repaired using laser cladding technology. The surface of the laser cladding region was then treated by deep surface rolling. Fatigue testing was subsequently conducted for the laser clad, deep surface rolled and post-heat treated laser clad specimens. It was found that deep surface rolling can significantly improve the fatigue life in comparison with the laser clad baseline repair. In addition, three dimensional residual stresses were measured using neutron diffraction techniques. The results demonstrate that beneficial compressive residual stresses induced by deep surface rolling can reach considerable depths (more than 1.0 mm) below the laser clad surface. © 2014 Elsevier B.V.
- ItemEffect of laser clad repair on the fatigue behaviour of ultra-high strength AISI 4340 steel(Elsevier, 2014-06-12) Sun, SD; Liu, Q; Brandt, M; Luzin, V; Cottam, R; Janardhana, M; Clark, GAThe fatigue behaviour of an ultra-high strength steel (>1800 MPa) was evaluated to assess the potential of using laser cladding as a repair tool for such steels in aeronautical structural applications. AISI 4340 and AerMet 100 steel powder were used to clad over a grind-out region in an AISI 4340 steel substrate using a 2.5 kW ND:YAG laser. Post-clad heat treatment (PCHT) was also investigated. Results showed very poor tensile properties and significantly reduced fatigue life of the AISI 4340 as-clad with a very high hardness and brittle fracture in the clad and HAZ zone. Residual stress results showed a compressive residual stress in the clad region and tensile residual stress in the HAZ. Changing the alloy of the clad layer to AerMet 100 steel, as well as applying a PCHT process, showed promising results as the fatigue life was improved from that of the grind-out substrate. © 2014, Elsevier B.V.
- ItemInvestigation into heat treatment and residual stress in laser clad AA7075 powder on AA7075 substrate(Springer US, 2013-06-04) Cottam, R; Luzin, V; Liu, Q; Wong, YC; Wang, J; Brandt, MThe laser cladding of AA7075 powder onto a AA7075 substrate was conducted to evaluate the effect of heat treatment and to measure residual stress between the clad layer and substrate to better understand the effect of laser cladding. The microstructure formed in the clad region was characteristic of a high cooling rate, which is typical for laser cladding. The heat-affected zone (HAZ) showed coarser precipitates when compared with the substrate and was attributed to the heating from the laser. A solution heat treatment followed by aging was employed to restore the strength in the HAZ. Nanohardness traverses of the clad and substrate was performed and it was shown the hardness in the 7075 clad layer was lower than the substrate both pre- and post-heat treatment and was attributed to the vaporization of zinc and magnesium. Neutron diffraction was employed to measure the residual stress both before and after heat treatment. The residual stresses formed in the clad layer were tensile and about 50 MPa in magnitude; heat treatment increased the stress level to approximately 100 MPa. © 2013, Springer.
- ItemPressure-modulated magnetism and negative thermal expansion in the Ho2Fe17 intermetallic compound(American Chemical Society, 2023-05-25) Cao, YL; Zhou, H; Khmelevskyi, S; Lin, K; Avdeev, M; Wang, CW; Wang, B; Hu, F; Kato,; Hattori, T; Abe, J; Ohara, K; Kawaguchi, S; Li, Q; Fukuda, M; Nishikubo, T; Lee, K; Koike, T; Liu, Q; Miao, J; Deng, JX; Shen, B; Azuma, M; Xing, XHydrostatic and chemical pressure are efficient stimuli to alter the crystal structure and are commonly used for tuning electronic and magnetic properties in materials science. However, chemical pressure is difficult to quantify and a clear correspondence between these two types of pressure is still lacking. Here, we study intermetallic candidates for a permanent magnet with a negative thermal expansion (NTE). Based on in situ synchrotron X-ray diffraction, negative chemical pressure is revealed in Ho2Fe17 on Al doping and quantitatively evaluated by using temperature and pressure dependence of unit cell volume. A combination of magnetization and neutron diffraction measurements also allowed one to compare the effect of chemical pressure on magnetic ordering with that of hydrostatic pressure. Intriguingly, pressure can be used to control suppression and enhancement of NTE. Electronic structure calculations indicate that pressure affected the top of the majority band with respect to the Fermi level (EF), which has implications for the magnetic stability, which in turn plays a critical role in modulating magnetism and NTE. This work presents a good example of understanding the effect of pressure and utilizing it to control properties of functional materials. © 2024 American Chemical Society
- ItemResidual stress measurements in laser clad aircraft aluminium alloys(ICMS Australasia, 2015-07-19) Zhuang, W; Liu, Q; Djugum, R; Sharp, PK; Paradowska, AMFatigue and corrosion damage of structural components threatens the safety and availability of civil and military aircrafts. There is no sign of relief from these threats as civil and military aircrafts worldwide are continuously being pushed further into and past their initial design fatigue lives in tight financial circumstances. Given fatigue and corrosion damage often initiates at the surface and sub-surface of the components, there has been extensive research and development worldwide focused on advanced aircraft repair technologies and surface enhancement methods. The Deep Surface Rolling (DSR) is one of advanced surface enhancement technologies that can introduce deep compressive residual stresses into the surface of aircraft metallic structure to extend its fatigue life. For the development of cost-effective aircraft structural repair technologies such as laser cladding, in this study, aluminium alloy 7075-T651 specimens with simulated corrosion damage were repaired using laser cladding technology. The surface of the laser cladding region was then processed by DSR. The experimental results from subsequent fatigue testing of laser cladded baseline, DSR and post-heat treated laser cladded specimens discovered that the DSR process can significantly increase fatigue life in comparison with the ascladded baseline. The three dimensional residual stresses were measured by neutron diffraction and the results confirmed the beneficial compressive residual stresses at the cladding surface can be achieved in depth more than 1.0 mm.
- ItemResidual stresses in Al7075 alloy laser cladded with Al-12Si alloy powder(The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2006-11-27) Durandet, Y; Bendeich, PJ; Ripley, MI; Liu, Q; Brandt, MCompared to conventional arc-welding processes commonly used to repair aluminium (Al) components, laser-cladding involves narrower heat affected zones (HAZ), lower overall heat input and less part distortion. With the development of high power lasers, it has become an attractive technology for the refurbishment of high value added structural airframe components in commercial and military aircrafts, especially those made of hard-to-weld age hardenable Al 7xxx series alloys. Laser cladding of 6.35mm thick rolled plates of Al7075 alloy was performed at IRIS using a high power Nd:YAG Laser and an Al-128i alloy powder as the filler repair material. Residual stress profiles through the clad plate thickness were measured using neutron diffraction scattering at ANSTO. Results showed the laser cladding pattern on residual stress profiles in directions longitudinal and transverse to the plate rolling direction. © The Authors
- ItemThe role of microstructure in the stress relaxation and tempering of laser clad Ti–6Al–4V(Elsevier, 2014-04-17) Cottam, R; Luzin, V; Liu, Q; Mayes, E; Wong, YC; Wang, J; Brandt, MIn this work a heat treatment procedure was performed on laser clad Ti–6Al–4V, which resulted in a reduction of tensile residual stresses in the clad samples as well and a decrease in the hardness of the clad layer with an increasing heat treatment time. The reduction in the residual stress was attributed to inter-phase stress relaxation brought about by the growth of the β phase. The reduction in hardness was attributed to an increase in the volume fraction of the soft β phase. Both the reduction in residual stress and hardness due to this heat treatment makes it an attractive method to heat treat both laser clad and additively manufactured Ti–6Al–4V components for improved mechanical properties.© 2014, Elsevier B.V.
- ItemSensitivity of nanostructure in charged cubosomes to phase changes triggered by ionic species in solution(American Chemical Society, 2013-11-07) Liu, Q; Dong, YD; Hanley, TL; Boyd, BJThe phase behavior of dispersions comprising mixed ionic surfactant and phytantriol was precisely controlled by varying the ionic surfactant content in the mixed lipid and the ionic strength in the system. Two important trends in the phase transition of the mixed lipid systems were identified: (1) An increase in the ionic surfactant content increased the curvature of the self-assembled system toward the hydrophobic region, resulting in the phase transition from cubic phase to lamellar phase. (2) An increase in ionic strength decreased repulsion between the headgroups of the ionic surfactant, resulting in a phase transition from lamellar phase to cubic phase. The phase transitions were confirmed using small-angle X-ray scattering and cryo-TEM and were strongly correlated with the visual turbidity of the dispersions. The lipid mixture with anionic surfactant showed high sensitivity to multivalent cations for triggering the phase transition, which may be a potential strategy to develop a detection/treatment system for toxic multivalent metallic cations such as chromium. © 2013, American Chemical Society.