Hardness Testing and Processing Conditions of Metal Alloys: A Case Study - Prof. Prince N., Lab Reports of Materials science

Download Hardness Testing and Processing Conditions of Metal Alloys: A Case Study - Prof. Prince N. and more Lab Reports Materials science in PDF only on Docsity! Use of Hardness Testing in Determining Processing Conditions and Ductility of Metal Alloys by Brad Peirson School of Engineering Grand Valley State University Laboratory Module 4 EGR 250 – Materials Science and Engineering Section 1 Instructor: Dr. P.N. Anyalebechi June 14, 2005 1 Abstract An experiment was run to measure the hardness of eleven metal samples. The identity of ten samples was known with the eleventh to be determined after the data had been examined. Ultimately it was determined that this sample closely resembled nodular cast iron. After the hardness data was assembled the average hardness of each sample was compared to both the calibration data for the hardness tester and to published hardness values. This comparison led to assumptions being made as to the processing conditions of each of the samples. After the processing conditions were determined the samples were ranked in order of increasing ductility. Finally a metal was chosen from the group for a wear resistant application based on this ranking. The hardest of the eleven samples, gray cast iron, was chosen for this application. 1 Introduction Hardness testing is a method by which the overall toughness of a material can be determined. There are several different scales that can be employed in hardness testing based on the material under examination. All of the different scales operate in the same manner. They also use the same equipment to obtain results. Hardness tests are performed on a hardness tester. The tester consists of an anvil that the specimen sits on during testing. An indenter is then pressed into the specimen. The type of indenter used, the weight used and the way the indentation is measured are the three ways that the proper hardness scale is determined. The Rockwell B scale uses a 0.1875 mm (1/16”) steel ball as the indenter with a mass of 100 kg. The other unique feature of the Rockwell B scale is the way in which the indentation is measured. A majority of the other hardness scales measure the diameter of the indentation in some manner whereas the Rockwell B scale measures the depth that the indenter penetrates the specimen [1]. The ductility of a specimen can be found based on the results of the hardness tests. Generally the harder a material is the less ductile it will be. Using this reasoning a 4 Table 2: Statistical Analysis of Eleven Metal Samples Hardness, RB Metal 1 2 3 µ R σ AA2024 80.5 80.7 80.4 80.5 0.3 0.2 AA6061 51.2 49.9 49.1 50.1 2.1 1.1 Phosphor Bronze 76.9 79.4 79.9 78.7 3.0 1.6 Brass 65.8 69.8 72.5 69.4 6.7 3.4 C1018 98.2 100.5 97.3 98.7 3.2 1.7 ? Cast Iron 101.1 101.1 100.1 100.8 1.0 0.6 Ductile Cast Iron 95.5 96.0 95.9 95.8 0.5 0.3 Gray Cast Iron 101.7 102.5 101.0 101.7 1.5 0.8 Cu 38.6 37.0 40.7 38.8 3.7 1.9 Ti 82.6 85.5 84.9 84.3 2.9 1.5 Stainless Steel 88.2 95.3 89.6 91.0 7.1 3.8 0.0 20.0 40.0 60.0 80.0 100.0 120.0 1 2 3 4 5 6 7 8 9 10 11 Metal H ar d n es s, R B Figure 1: Average Hardness Across 11 Metal Samples, Ordered as in Table 1 5 Table 3: Average Hardness Values For Eleven Metal Samples with Published Hardness Values and Processing Conditions Published Metals µ, RB Hardness, RB Condition Source AA2024 80.5 80 T361 [2] AA6061 50.1 26 T451 [2] Phosphor Bronze 78.7 73 C50500-H06 [2] Brass 69.4 70 C27000-H02 [2] C1018 98.7 92 Carburized [2] ? Cast Iron 100.8 100 Nodular [2] Ductile Cast Iron 95.8 96 80-55-06 [2] Gray Cast Iron 101.7 100 Class 50 [2] Cu 38.8 40 C10100-H02 [2] Ti 84.3 80 Grade 4 [3] Stainless Steel 91.0 88 18 CR-CB [2] 0.0 20.0 40.0 60.0 80.0 100.0 120.0 A A 20 24 A A 60 61 Ph os ph or B ro nz e Br as s C1 01 8 ? C as t I ro n D uc til e C as t I ro n G ra y C as t I ro n C u Ti St ai nl es s S te el Metal H ar d n es s, R B Average Hardness Published Hardness Figure 2: Comparison of Average Hardness Values to Published HardnessValues 6 Table 4: Presence of Alloying Elements in Metal Samples Metal Alloying element Wt. % in Sample AA2024 Cu 3.8-4.9 Mg 1.2-1.8 Mn 0.3-0.9 AA6061 Cr 0.04-0.35 Cu 0.15-0.4 Mg 0.8-1.2 Si 0.4-0.8 Phosphor Bronze Cu 98.75 Sn 1-1.7 Yellow Brass Cu 63-68.5 Zn 31.3-37 C1018 C 0.14-0.2 Mn 0.6-0.9 Ductile Cast Iron C 3.6-3.8 Ce 0.005-0.2 Cr 0.03-0.07 Cu 0.15-1 Fe 90.738-94.175 Mg 0.03-0.06 Mn 0.15-1 Mo 0.01-0.1 Ni 0.05-0.2 Si 1.8-2.8 9 Based on the hardness values given in Table 2 the metal samples can be arranged according to their ductility. Hardness relates to ductility on that the harder the material, the less ductile it should be. The metal samples, ranked from least to most ductile, are gray cast iron, nodular cast iron, C1018 steel, ductile cast iron, stainless steel, titanium, aluminum alloy 2024, phosphor bronze, brass, aluminum alloy 6061 and copper. The above ductility ranking can in turn be used to determine which of the metals tested would be best suited for a high wear application. The ranking is based on ductility, which is essentially the opposite of hardness. Therefore the least ductile of the samples would be best suited for a wear resistance application. In this case, the gray cast iron had the highest hardness of the metal samples. This is the metal that would have the highest wear resistance property. The error in this experiment is two-fold. The major source of error would be the location of the hardness test. Each time a sample is hardness tested is becomes slightly harder around the test location because of the deformation. If the indenter were located too close to a previous test site in running this experiment the results would be slightly off. The other error would be in the limitations of the Rockwell B scale. Rockwell be is considered valid in the range of 40 RB to 100 RB [1]. There were several samples that had measurements close to the upper extreme of this range and a few went beyond. The metals AA6061 and Copper were at the extreme bottom of the range. Because of this the actual hardness of the sample may vary considerably from what was measured. 5 Conclusions 1) The variability in the hardness tester suggests that the material is not homogeneous in nature. 2) The variability in the test samples was closely related to that of the calibration plate. 10 3) Treatment conditions seem to have a great effect on individual alloys in the same family of alloys. 4) The test materials seem to have been measured correctly as they closely correlate to published hardness values. 5) The rankings of the test samples in order of increasing ductility is gray cast iron, nodular cast iron, C1018 steel, ductile cast iron, stainless steel, titanium, aluminum alloy 2024, phosphor bronze, brass, aluminum alloy 6061 and copper. 6) Gray cast iron would appear to be the most appropriate material in a wear resistance application. 6 References 1. P.N Anyalebechi: “Materials Science and Engineering” 2. Matweb – Material Property Data, www.matweb.com, June 12, 2005. 3. Metal Suppliers Online: Material Property Data – Titanium CP Grade 4, www.materialsuppliersonline.com, June 12, 2005. 4. W. Zhang, G.S. Frankel: Transitions Between Pitting and Intergranular Corrosion in AA2024, Electrochimica Acta, 2003, pp. 1193-1210. 5. Heat Treating of odular Irons: Part One, www.key-to-steel.com, June 12, 2005.