Sliding wear behavior of some Al-Si alloys: Role of shape and size of Si particles and test conditions
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I.
INTRODUCTION
ALUMINUM-silicon alloys have been used in tribocomponents involving sliding movement with a contacting counterbody.[1–6] The response of these components greatly depends on their material-related parameters, e.g., the nature, shape, size, content, and mode of distribution of given microconstituents. Also, service/test conditions influencing the wear characteristics of materials include load, speed, temperature, environment, counterbody roughness, and configuration of the sliding pair, relative to a constant design aspect.[1–14] It has been observed that even a minor alteration in any of the parameters can change the sliding wear behavior significantly. Thus, it is essential to characterize the material for their mechanical properties and sliding wear behavior in as many situations as possible. This would enable us to develop a better understanding about the response B.K. PRASAD, Scientist, is with the Regional Research Laboratory (CSIR), Habibganj Naka Bhopal - 462 026, India. K. VENKATESWARLU, Scientist, is with the National Metallurgical Laboratory (CSIR), Jamshedpur - 831 007, India. O.P. MODI, A.K. JHA, S. DAS, R. DASGUPTA, and A.H. YEGNESWARAN, Scientists, are with the Regional Research Laboratory (CSIR), Habibganj Naka, Bhopal - 462 026, India. Manuscript submitted December 8, 1997. METALLURGICAL AND MATERIALS TRANSACTIONS A
of the material under different conditions. Significant efforts have been made to examine the effects of test variables, e.g., load, speed, and environment, on the sliding wear behavior of the Al-Si alloys.[1–4,6–14] However, the microstructural aspects have had less attention in this context.[7–14] In view of this discussion, sliding wear characteristics of some Al-Si alloys have been studied in this investigation under varying test pressures and speeds. Further, the influence of the shape and size of Si particles on the mechanical and wear properties of the alloys has also been investigated. II.
EXPERIMENTAL
Experimental alloys (Table I) were prepared by foundry (i.e., melting and casting) technique. Permanent molds were used for shaping the alloy melt. Samples were polished per standard metallographic techniques and etched with Keller’s reagent to reveal their microstructural features. Hardness values of the metallographically polished samples were measured using a Vicker’s hardness tester. Tensile tests were conducted on round samples having a 6-mm gage diameter and a 32-mm gage length. The samples were tested at a strain rate of 1.04 3 1023/s. Dry sliding wear tests were conducted on 6-mm-diameter, 40-mm-long cylindrical specimens. The counterface VOLUME 29A, NOVEMBER 1998—2747
Table I.
Serial Number 1 2 3
Designation and Mechanical Properties of Experimental Al-Si Alloys
Alloy LM13 GC LM29 GC LM29 PC
Hardness (HV)
Tensile Strength Elongation MPa
Pct
105
151
1.5
124
122
1.0
156
140
1.5
GC: gravity cast, and PC: pressure cast.
alloy (Figure 2(b)) with the noted exception of the refined microconstituents (Figure 2(c)). The extent of refinement in
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