Coherent Interfaces Increase Strain-Hardening Behavior in Tri-Component Nano-Scale Metallic Multilayer Thin Films

Figures & data

Figure 1. Hardness measurements from nanoindentation experiments conducted using a Berkovich tip (effective strain 8%) and cube-corner tip (effective strain 22%), approximating the hardening response of multilayer films with mixed interfaces (tri-layer) and incoherent interfaces (alloy).

Figure 2. Representative stress–strain curves from micro-pillar compression testing of NMMs for (a) tri-layer (mixed interfaces) and (b) the bi-layer alloy (incoherent interface only) films.

Table 1. Strength- and work-hardening summary for tri-layer and alloy films tested using micro-pillar compression and nanoindentation.

		Micro-pillar compression				Nanoindentation
Sample		σys (GPa)	σmax (GPa)	n, Ludwik	Eng. stress at 8% (GPa)	Berkovich-8% (GPa), H/2.7 [8]
5 nm Tri-layer	P1	1.48	2.17	0.50	2.01	1.63 ± 0.06
	P2*	1.57	2.32	0.54	2.23
30 nm Tri-layer	P1	1.44	1.85	0.35	1.83	1.4 ± 0.12
	P2*	1.18	1.53	0.39	1.51
5 nm Alloy	P1	1.64	2.60	0.42	2.34	2.1 ± 0.04
	P2*	1.82	2.24	0.41	2.15
30 nm Alloy	P1	1.32	1.75	0.31	1.68	1.62 ± 0.03
	P2*	1.36	1.68	0.34	1.65

Stress–strain curves shown in Figure 3 are noted with *.

Figure 3. Undeformed (left) and post mortem (right) pillars of mixed interface tri-layer films and incoherent interface alloy films showing difference in deformation as a result of interface type and layer thickness.

Tabor D. The hardness of metals. Oxford: Oxford University Press; 1951.

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