S1. Fabrication and Laser shock peening of AA 6061-graphene nanocomposites

Gas atomised, near spherical shape AA 6061 (~ 10 µm in dia, >99.98% purity) supplied

by Ampal Inc. NJ, the USA is shown in Fig.S1a, and Fig.S1b summarises the various elements.

Fig.S2a & S2b shows the transmission electron microscopic nano-flakes (TEM; Tecnai, G2 20

Twin) of graphene along with SAED pattern inset. Fig.S3 shows the schematics of the

fabrication method and Fig.S4 Schematic of peening process of AA 6061 – graphene

nanocomposites along with laser peening parameters are given in Table.S1.

Fig.S1 (a) SEM morphology and (b) X-ray fluorescence spectroscopic profile of AA 6061

alloy powder

Fig.S2 TEM nanostructures of (a) nano-flake and (b) high-resolution single atomic layer of

graphene (inset: shows the SAED pattern)

(b)(a)

Fig.S3 Schematics of fabrication method of AA 6061 – graphene nanocomposites

Fig.S4 Schematic representation of (a) laser shock peening processing (b) laser pulse

propagation on the AA 6061 – graphene nanocomposites

Table.S1 Laser shock peening process parameters

S2. Summary of tensile test results

Table.S2 Summary of tensile test results

Samples

Ultimate Tensile

Strength (UTS)

MPa

Elongation

(%)

Proof stress

(MPa)

Young’s

modulus

(GPa)

AA 6061 225 16.76 151.63 64.62

AA 6061 – Graphene 348 14.50 171.85 71.19

AA 6061 – Graphene -

LSPed439 12.84 184.96 72.25

Experimental parameters Values

Pulse energy (Ep) 200 mJ

Laser spot diameter (D) 0.8 mm

Pulse density (Np) 1600 pulse/cm2

Pulse duration 10 ns

Wavelength (λ) 1064 nm

Coverage (C) 11

Power density (P) 5 GW/cm2

Extrusion direction

30˚

45˚

0˚

S3. Anisotropic behaviour of laminated composites

Fig.S7 Schematics of wire cut tensile sample along various orientation with respect to extrusion

direction (b) E8 - 04 tensile specimen dimensions (c) Tensile test in INSTRON – 8801

S4. Hardness and Residual stress profile

Fig.S6 Vickers microhardness along transverse cross-section of AA 6061-graphene nanocomposites

Fig.S8 Residual stress profile of AA 6061-graphene nanocomposites

S6. Fully reversed high cycle fatigue studies

Table.S3 High-cycle fatigue test results

Specimen

Manufacturing

Process

Fatigue life

(×105 cycles)

Specimen 1

Fatigue life

(×105 cycles)

Specimen 2

Fatigue life

(×105 cycles)

Specimen 3

Fatigue life

(×105 cycles)

Specimen 4

Unpeened AA 6061

Graphene reinforced1.04 1.22 0.98 1.13

LSP AA 6061

Graphene reinforced3.71 2.11 3.41 2.97

50% pre fatigued+

LSP2.3 2.04 1.8 2.10