Relationship Between Machinability, Microstructure, and Mechanical Properties of Al-7Si Alloy

Abstract

In this work, commercially available Al-7Si alloy was used, and the microstructure was modified by the additions of AlSr15, AlTi5B1, and Al3B. Cylindrical samples were cast into a sand mold and the machinability of the alloys was characterized by means of surface roughness, chip morphology, and buildup edge of the chips. Tool life and surface finish can be improved by decreased chip size by lowering the energy required for machining. The surface finish is an indicator of the quality of the material during the machining process. Therefore, in addition, melt quality was measured by means of reduced pressure test and the calculation of the bifilm index was used to compare the melt quality with machinability. It was found that there is a good correlation between bifilm index and surface roughness of the machined parts. Thus, for a better surface finish, melt quality, which can be quantified by bifilm index, has to be high. AlSr15 modified alloy exhibits the lowest built-up edge with the lowest surface roughness, because strontium modification causes coarse silicon crystals to transform to fine fibrous structure, which enhances machinability.

Tool Wear and Milling Characteristics for Hybrid Additive Manufacturing Combining Laser Powder Bed Fusion and In Situ High-Speed Milling

“…A twentyfold tool magazine allows changing the milling device, e.g., for roughing and finishing purposes, again not differing to industrial high-speed milling machines. Contrary to conventional milling processes, however, no cooling lubricant can be used as milling is performed within the powder bed, posing challenges such as, e.g., elevated temperature conditions or increased tool wear [ 28 , 29 , 30 , 31 ]. To access the tool wear properties in our study, we used previously determined milling parameters as given by Table 2 [ 20 ].…”

Influence of Lathe Rotation and Secondary Dendritic Arm Spacing on Surface Roughness of an Al-3wt.%Si Alloy Submitted to the Necking Process

“…Recent studies have analyzed the significant correlation between microstructural parameters of solidification and machinability, however, although it is well-known how much the solidification process and the formed structures influence the machinability of the materials, there are few studies in the literature that do this analysis in nonferrous alloys [6,7]. Silva et al [8], when analyzing the correlation between shear temperature, tool wear and the microstructure in the columnar zone of an Al-7wt.%Si alloy, solidified in a horizontal directional system, observed that the maximum and average cutting temperatures increased and that the edge flank wear has decreased with increasing secondary dendritic arm spacing.…”

Correlation between the microstructure and machinability in machining Al–(5–25) wt% Si alloys

“…In fact, transformation of coarse silicon particles to fine fibrous structure enhances the machinability of hypoeutectic Al−Si alloys by exhibiting the lowest BUE. 28…”

“…In fact, transformation of coarse silicon particles to fine fibrous structure enhances the machinability of hypoeutectic Al2Si alloys by exhibiting the lowest BUE. 28 The cutting force in machining Al2Si alloys also decreases at high cutting speeds. The reason can be attributed to the reduction of BUE at high cutting speeds.…”