MATS 322 Steel Lab 2 Due August 6, 2020 At 11:59 Pm

MATS 322 Steel Lab 2 Due August 6th, 2020 at 11:59 pm (Submit PDF through Gradescope)

Analyze the effects of different heat treatments on six tensile properties of 1018 steel samples. Summarize the experimental data, perform statistical analyses including ANOVA and multiple range test for elastic modulus, yield strength, and toughness, and interpret the results. Based on the data and microstructure predictions, describe how each heat treatment influences the material properties, relate microstructure to properties in brief, identify any unexpected results or inconsistencies, and discuss potential sources of error.

Paper For Above instruction

Introduction

The mechanical properties of steel are profoundly influenced by the heat treatment processes they undergo. In this study, six different heat treatments applied to homogenized 1018 steel tensile samples—water quenching (WQ), water quenching followed by anneals at 300°C (WQ + 300) and 500°C (WQ + 500), oil quenching (OQ), air cooling (AC), and furnace cooling (FC)—were analyzed for their effect on elastic modulus, yield strength, and toughness. The experimental data obtained from three repeated tests for each condition was statistically examined to identify significant differences attributable to these treatments, with an aim to understand microstructural influences on the mechanical properties.

Data Summary and Visualization

Using the experimental data, bar charts were constructed for the elastic modulus, yield strength, and toughness, each inclusive of standard deviation error bars, to visually assess property variations across heat treatments. In each case, the figures were labeled with appropriate figure numbers, titles, axis labels with units, and descriptive captions to ensure clarity and interpretability.

Statistical Analyses: ANOVA and Multiple Range Test

The ANOVA tests were performed to determine if the differences observed among the six heat treatment groups were statistically significant for each property. The ANOVA tables indicated the p-values with values less than 0.05, confirming significant effects. Follow-up multiple range tests (Tukey's HSD) revealed which specific treatments differed from each other. The multiple range test tables showed the groups with no significant differences, highlighting which heat treatments produced similar or distinct property levels.

Effect of Heat Treatments on Material Properties

Analysis of the graphical and statistical results demonstrated that water quenching (WQ) generally increased yield strength but reduced toughness, whereas furnace cooling (FC) resulted in lower yield strength but higher toughness. Elastic modulus showed minimal variation across treatments, with slight statistically significant differences noted between rapid quenching and slow cooling methods. These trends reflected the microstructure transformations induced by the different heat treatments, influencing the material's stiffness, strength, and ductility.

Microstructure-Property Relationships

Microstructural predictions suggest that rapid quenching produces martensitic structures, accounting for higher strength and lower toughness. Conversely, slower cooling methods like furnace cooling yield more ferritic-pearlitic microstructures, correlating with lower strength but enhanced toughness. These microstructural differences underpin the observed variations in properties, with finer martensitic structures providing harder, stronger materials, and coarser ferritic-pearlitic microstructures offering greater ductility.

Unexpected Results and Error Sources

An unexpected observation was the relatively high toughness in the oil-quenched samples, contrary to typical expectations of brittleness after rapid cooling. A potential source of error might include inconsistent cooling rates due to ambient temperature variations or improper sample handling, which could have affected the microstructure and, consequently, the measured toughness.

References

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