We elucidate here the impact of multiaxial forging of Mg-2Zn-2Gd alloy on grain refinement to sub-micron regime and relate the structure to mechanical properties. As-cast and annealed samples were multiaxial forged (MAF) for a total number of two passes with a true strain of ∼2/pass. Using only two passes, multiaxial forging successfully reduced the average grain size to less than a ∼1 μm. When the annealed samples were forged, the yield strength increased to ∼227 MPa as compared to the as-cast alloy with yield strength of ∼54 MPa. The improvement in mechanical properties is attributed to the homogeneous structure obtained on annealing, which led to high degree of grain fragmentation. Annealing also led to fine distribution of precipitates, which significantly improved strength and hardness. The Rockwell hardness (HRE) was ∼88 for annealed and forged alloy in relation to ∼55 for the as-cast alloy. © 2016 Elsevier B.V.

R. Jayganthan

Annealing

Biomaterials

Forging

Gadolinium alloys

Grain size and shape

Hardness

Magnesium alloys

Mechanical properties

Rare earths

Yield stress

Zinc

Annealed samples

AS CAST ALLOY

Average grain size

FORGED ALLOYS

Grain fragmentation

HOMOGENEOUS STRUCTURE

MULTIAXIAL FORGING

ROCKWELL HARDNESS

Grain refinement

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Materials Science and Engineering A

In this paper, room temperature forging (RTF, 25 °C) and warm forging (WF, 200 °C) of Al-Mg-Si alloy were performed, for strengthening the 6082 Al alloy at low applied strain. Overall WF-AlMgSi alloy forged just after 2 cycles (1.26 true strain) exhibits maximum hardness, tensile strength, J-integral value, and plastic strain in all investigated samples. This is due to: (i) the formation of ultrafine grain (UFG) of size 411 nm, (ii) the formation of stress free dynamic recrystallized (DRX) grains, and (iii) the complete precipitation of β"-phase. The UFG increased the hardness and yield strength (YS) according to the conventional Hall-Petch effect, and the β"-phase increased the hardness and the YS by providing the obstacle to the movement of mobile dislocations. The stress free DRX grains accommodate a large number of mobile dislocations, which further enhances the plastic strain. The UFG, the DRX grains, and the β"-phase effect, all combined together further enhance the J-integral value. The effects of RTF, WF and strains on the emergence of various forms of shear bands were also discussed in this paper. Softening effect on both RTF and WF-AlMgSi alloy after processing beyond 2 cycles is due to factors such as saturation of strengthening through Hall-Petch effect and coarsening of β"-phase in the RTF-AlMgSi alloy and β'-phase in the WF-AlMgSi alloy, respectively. © 2019

Materials Characterization

Al 6082 alloy strengthening through low strain multi-axial forging

The effect of rolling at elevated temperature on mechanical behaviour of bulk Mg-4Zn-4Gd alloy was investigated. The alloy was subjected to solution treatment at 673 K for 24 h, followed by flat and cross rolling at elevated temperature (723 K). The microstructure of ultrafine grains (less than ~1 µm size) was successfully achieved from solutionized sample with grain size ~78 µm after the rolling process, which has significantly influenced the mechanical behaviour of the deformed Mg alloy. The yield strength (YS), ultimate tensile strength (UTS), elongation-to-failure (%E) and hardness of a rolled specimen have enhanced maximum up to the value of 276.3 ± 13 MPa, 341.3 ± 7 MPa, ~26.1% and 74.2 ± 2 HV, respectively. The improvement in mechanical properties of processed Mg alloys due to the combined effect of grain refinement and secondary phase (W-phase) distribution into the Mg matrix upon the repetitive rolling process. In addition, the improvement in tensile properties is explained by correlating the dislocation density (ρ), scanning electron (SEM) and transmission electron (TEM) micrographs. The developed intrinsic property of rolled specimens is substantiated by tensile fractography obtained from SEM equipped with energy dispersive X-ray spectroscopy (EDS). Various other microstructural features were also revealed by TEM and X-ray diffraction (XRD) analysis. The anisotropy of various rolled Mg-4Zn-4Gd specimens was also elucidated on the basis of tensile results. © 2017 Elsevier B.V.

Studies on tensile behaviour and microstructural evolution of UFG Mg-4Zn-4Gd alloy processed through hot rolling

In recent years, magnesium alloys have attracted significant attention as a new class of biodegradable implant materials, because of their superior biocompatibility and low modulus. We describe here the inhibition of bacterial colonisation and biofilm formation on surfaces of Mg-2Zn-2Gd alloy with different grain structures (~44 µm to ~710 nm) obtained via multiaxial forging. Surface energy and contact angle measurements using goniometer and wettability were assessed with water, SBF, n-Hexane and DMEM. The higher surface energy of ultrafine-grained Mg-2Zn-2Gd alloy led to the release of more Mg+2 ions at an early stage, which consequently increased the pH of fluid in the vicinity of the implant, therefore producing unfavourable environment for the survival of Escherichia coli (E. coli) bacteria. This led to damage of bacterial cell walls thereby reducing their adhesion. In summary, the study underscores that grain size had a significant impact on antimicrobial behaviour. © 2016 Informa UK Limited, trading as Taylor & Francis Group.

Materials Technology

Cellular response of Escherichia coli to Mg-2Zn-2Gd alloy with different grain structure: mechanism of disruption of colonisation

Materials Science and Engineering: C

Biocompatibility of ultrafine grained zircaloy-2 produced by cryorolling for medical applications

Materials & Design

Manufacturing of open-cell Mg foams by replication process and mechanical properties

Microstructures, mechanical and cytocompatibility of degradable Mg–Zn based orthopedic biomaterials

Materials Science and Engineering: A

Investigations on microstructures, mechanical and corrosion properties of Mg–Gd–Zn alloys

Applied Surface Science

Characterization and in vitro biocompatibility study of Ti–Si–N nanocomposite coatings developed by using physical vapor deposition

Grain refinement to submicron regime in multiaxial forged Mg-2Zn-2Gd alloy and relationship to mechanical properties

Journal	Data powered by TypesetMaterials Science and Engineering A
Publisher	Data powered by TypesetElsevier Ltd
ISSN	09215093
Open Access	No