Physical, Mechanical, and Tribological Attributes of Stir-Cast AZ91/SiCp Composite

doi:10.1007/s40195-014-0045-3

Abstract

Abstract:

In the present investigation, composites with silicon carbide particle (SiC_p) as reinforcement and AZ91 magnesium alloy as matrix have been synthesized using liquid metal stir-casting technique with optimized processing conditions. The composites with good particle distribution in the matrix, and better grain refinement and good interfacial bonding between the matrix and reinforcement have been obtained. The effect of SiC_p content on the physical, mechanical, and tribological properties of Mg-based metal matrix composite (MMC) is studied with respect to particle distribution, grain refinement, and particle/matrix interfacial reactions. The electrical conductivity, coefficient of thermal expansion, micro- as well as macro-hardness, tensile and compressive properties, and the fracture behavior of the composites along with dry sliding wear of the composites have been evaluated and compared with the base alloy.

Key words: Composite, AZ91D alloy, Casting alloy, Mechanical properties, Wear

K. K. Ajith Kumar, Abhilash Viswanath, T. P. D. Rajan, U. T. S. Pillai, B. C. Pai. Physical, Mechanical, and Tribological Attributes of Stir-Cast AZ91/SiC_p Composite[J]. Acta Metallurgica Sinica (English Letters), 2014, 27(2): 295-205.

Figures/Tables 14

Fig. 1 Schematic diagram of tensile specimen (unit: mm)

Table 1 Measured density (ρmc), theoretical density (ρth), and porosity (P) of AZ91 alloy and AZ91/SiCp composites and the volume fraction of SiCp (Vr)

Material	ρ_mc (g/cm³)	V_r (vol%)	ρ_th (g/cm³)	P (vol%)
AZ91	1.804	–	1.810 [12]	0.33
AZ91/5SiC_p	1.834	2.9	1.841	0.38
AZ91/10SiC_p	1.873	5.9	1.883	0.53
AZ91/15SiC_p	1.913	9.0	1.926	0.67
AZ91/20SiC_p	1.955	12.3	1.972	0.86
AZ91/25SiC_p	1.988	15.8	2.021	1.09

Table 2 Physical properties of AZ91 and AZ91/SiCp composites

Material	Conductivity (%IACS)	Theoretical conductivity (%IACS)	CTE (10^-6/K)	Theoretical CTE (10^-6/K)
AZ91	12.70	12.70	25.69	25.69
AZ91/5SiC	12.60	12.36	23.24	25.04
AZ91/10SiC	11.00	12.05	22.38	24.45
AZ91/15SiC	10.57	11.70	21.68	23.77
AZ91/20SiC	10.17	11.58	20.26	23.54
AZ91/25SiC	10.11	11.31	18.25	23.01

Fig. 2 XRD plots of AZ91 a and AZ91/SiCp composites with 5 wt% b, 10 wt% c, 15 wt% d, 20 wt% e, 25 wt% f SiCp additions

Fig. 3 Optical micrographs of AZ91 alloy a and AZ91/SiCp composites with 5 wt% b, 10 wt% c, 15 wt% d, 20 wt% e, 25 wt% f SiCp additions

Fig. 4 Microstructures of AZ91 alloy showing grain size a, AZ91/10SiCp composite showing reduced grain size b

Fig. 5 SEM micrograph of AZ91/10SiCp composite a, the SEM micrograph with high magnification depicting the cleaner interface between the reinforcement and the matrix b

Table 3 Mechanical properties of AZ91 and AZ91/SiCp composites

Material	Macrohardness (BHN)	Microhardness (HV)	YS (MPa)	UTS (MPa)	UCS (MPa)
AZ91	63	63	92	187	310
AZ91/5SiC	82	338	112	184	317
AZ91/10SiC	86	346	124	182	334
AZ91/15SiC	90	358	127	182	344
AZ91/20SiC	92	360	136	184	353
AZ91/25SiC	97	364	141	184	364

Fig. 6 Typical fracture surfaces of the tensile tested specimens of AZ91 alloy a, AZ91/5SiCp composite b, AZ91/15SiCp composite c, AZ91/25SiCp composite d

Fig. 7 SEM micrographs of AZ91/SiCp composite polished just below the fracture surface showing cracked particles a, debonding of particles b

Fig. 8 Histogram showing wear rate vs. SiCp content a, coefficient of friction vs. SiCp content b

Fig. 9 SEM images of worn surfaces: a AZ91/10SiCp tested at 19.6 N; b AZ91/10SiCp tested at 39.2 N; c AZ91/25SiCp tested at 19.6 N; d AZ91/25SiCp tested at 39.2 N

Fig. 10 SEM images of the wear debris: a AZ91/10SiCp tested at 19.6 N; b AZ91/10SiCp tested at 39.2 N; c AZ91/25SiCp tested at 19.6 N; d AZ91/25SiCp tested at 39.2 N

Fig. 11 SEM images of wear debris showing Mg ribbons suggesting abrasion wear a, fine Mg oxides on the wear debris b

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