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GVSU EGR 250 - The Effects of Composition on the Hardness Property of Metals

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1The Effects of Composition on the Hardness Property of MetalsbyDan SchwarzSchool of EngineeringGrand Valley State UniversityLaboratory Module 4EGR 250 – Material Science & EngineeringSection 01Instructor: Dr. P.N. AnyalebechiFebruary 21, 20062AbstractHardness is the quality of a material that allows it to withstand deformation. A variety ofrelative scaling methods such as the Rockwell hardness scale can be used to quantify thehardness of a material. Composition, microstructure and processing conditions of a material allcontribute to its hardness but the following hardness experiment is only aimed at establishing arelationship between the composition and hardness characteristics of several metal samples. Themetal samples are tested using the Rockwell B scale and the material compositions are comparedwith the resulting hardness values. Ferrous materials such as cast irons and steels were found tobe generally harder than non-ferrous materials such as aluminum alloys, copper alloys, andtitanium. Overall, the metals were hardened by increased amounts of alloying materials.IntroductionIn the context of material science, hardness is a mechanical property which allows amaterial to resist “localized plastic deformation”. [1] The hardness of a material is commonlyquantified using Rockwell, Brinell, and Vickers methods. In general, these methods define thehardness of a material in terms of the amount of deformation produced by a loaded indenter thatis harder than the test specimen. Hardness testing produces relative hardness values sincedifferent indenters and loading methods create unique indentations on the same test specimen.Engineering materials exhibit a wide range of hardness values that depend on theircomposition, microstructure, and processing methods. The main objective of the followingexperiment is to explore the relation between hardness and composition of thirteen metallicengineering materials. These materials have a wide range of compositions that can be dividedinto ferrous and non-ferrous categories with subgroups that contain various alloys. Obtaininghardness values for each material with the Rockwell B test provides a framework for comparingmaterial compositions to their respective hardness properties.Experimental ProcedureThe Rockwell hardness tester was set to the B scale by selecting a test load of 100kg andby using a 1.588mm diameter ball indenter. A standard material with a known value of 89.3±1.03RB was tested seven times by the Rockwell tester to determine its accuracy. The values derivedfrom the standard material are shown in Table 1.Table 1 : Standard RB material values.Standard 89.3±1.0 RBTest No. RB Hardness1 89.72 90.43 90.14 90.45 88.76 907 90.2All of the test values in Table 1 are higher than the standard except for the value takenfrom test number 5. Table 1 suggests that the Rockwell tester is producing values that are justslightly higher than the actual B scale. This may account for a small amount of discrepancy inthe experimental values.After determining the accuracy of the Rockwell tester, each material sample was set onthe anvil and raised up to the indenter. The Rockwell tester automatically placed the minor andmajor loads on the indenter and calculated the RB constant. Three tests were performed on eachmaterial and the values were recorded.ResultsThe experimental results obtained from the sample materials are summarized in Table 2.The average hardness is given for each material to provide an accurate depiction of the relativestanding for each material. Also included in the table is the standard deviation to describe thespread of the hardness values for each sample.Table 2 : Experimental hardness results for the test samples.RB HardnessMetal Sample 1 2 3 Mean Standard DeviationDuctile Cast Iron 99.9 98.4 99.0 99.1 0.75Grey Cast Iron 98.4 98.2 99.6 98.7 0.76White Cast Iron 93.9 94.4 95.2 94.5 0.66C1018 91.7 91.7 92.1 91.8 0.23C1045 100.9 100.8 100.3 100.7 0.324140 90.5 92.2 94.8 92.5 2.17Stainless Steel 86.8 87.4 85.8 86.7 0.81AA2024 75.4 78.7 77.2 77.1 1.654AA6061 52.7 52.7 52.9 52.8 0.12Pure Copper 27.4 31.6 34.1 31.0 3.39Brass 62.6 62.4 63.0 62.7 0.31Phosphorous Bronze 84.3 78.5 76.1 79.6 4.22Titanium 83.4 83.1 88.7 85.1 3.15The first seven ferrous metals are on the high end of the Rockwell B scale with valuesranging from 85 to 100 RB. Within the ferrous group are subgroups of cast irons and steels. Thecast irons have hardness values in the mid to upper nineties whereas the steels range from thelow nineties to the low one hundreds. The last six non-ferrous metals are on the lower end of the Rockwell B scale with valuesranging from 27 to 84 RB. Within the non-ferrous group are subgroups of aluminum alloyscopper alloys and titanium. The aluminum alloys range from 52 to 78 RB, the copper alloysrange from 27 to 88 RB, and titanium ranges from 83 to 88 RB. DiscussionThe material compositions corresponding to the results in Table 2 are given in Table 3. Table 3 : Approximate composition of the test samples.Metal Sample Composition ReferenceDuctile Cast Iron Fe - 3.0-4.0 wt. % C, 1.8-2.8 wt. % Si, 0.1-1.0 wt. % Mn, 0.01-0.03 wt. % S, 0.01-0.1 wt. % P Atlas foundry co. Grey Cast Iron Fe - 2.5-4.0 wt. % C, 1.0-3.0 wt. % Si, 0.2-1.0 wt. % Mn, 0.02-0.25 wt. % S, 0.02-1.0 wt. % P Atlas foundry co. White Cast Iron Fe - 2. -2.9 wt. % C, 0.9-1.9 wt. % Si, 0.15-1.2 wt. % Mn, 0.02-0.2 wt. % S, 0.02-0.2 wt. % P Atlas foundry co. C1018 Fe - 0.14-0.2 wt. % C, 0.6-0.9 wt. % Mn, 0.05 (max) wt. % S, 0.04 (max) wt. % P Matweb C1045 Fe - 0.43-0.5 wt. % C, 0.6-0.9 wt. % Mn, 0.05 (max) wt. % S, 0.04 (max) wt. % P Efunda.com 4140 Fe - 0.38-0.43 wt. % C, 0.7-1 wt. % Mn, 0.8-1.1 wt. % Cr, 0.15-0.25 wt. % Mo, 0.15-0.3 wt. % Si Matweb Stainless Steel Fe - 18-20 wt. % Cr, 8-12 wt. % Ni, 2 (max) wt. % Mn, 1 (max) wt. % Si Matweb AA2024 Al - 3.8 - 4.9 wt. % Cu, 0.3 - 0.9 wt. % Mn, 1.2 - 1.8 wt. % Mg ASM aerospace inc.AA6061 Al - 0.15 - 0.4 wt. % Cu, 0.15 (max) wt. % Mn, 0.8 - 1.2 wt. % Mg, 0.4 - 0.8 wt. % Si Matweb Pure Copper 100 wt. % Cu Matweb Brass Cu - 39.25 wt. % Zn, 0.5 - 1 wt. % Sn, 0.02 - 0.1 wt. % P Matweb Phosphorous Bronze Cu - 1-1.75 wt. % Sn, 0.3 (max) wt. % Zn, 0.35 (max) wt. % P Matweb Titanium Ti - 0.3 (max) wt. % Fe, 0.25 (max) wt. % O, 0.1 (max) wt. % C Matweb The materials with the highest hardness values were all


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