Materials Engineering Department
BS in Materials Engineering
Liquid propellant rocket diaphragms require extreme ductility. 1100 Aluminum is used for its high ductility, but the post-processing cold work and subsequent anneal result in excessively large grains. The effect of heat treatment and cold work on grain size in 1100 aluminum was explored. The samples were cold worked to 0, 5, 10, 15 and 30% using tensile elongation. The samples were then heat treated per AMS 2770 with either a "Steel Conduction" (1000 – 1150°F/min) or a "Production" (16 – 18°F/min) heating rate. The grain size of the samples were measured using the mean lineal intercept method. The grain diameter ranged from 81 – 189 μm for the Production rate and 83 – 209 μm for the Steel Conduction rate. The 15% cold worked Production rate samples were found to have significantly larger grains than those of the smaller cold work amounts as well as the 15% cold worked Steel Conduction rate samples. This indicated an interaction between the 15% cold work amount and the Production heat treatment which allowed for significant grain growth. The 30% cold worked samples were found to have grain growth in both heat treatments with the largest average grain diameters. The results indicate that the longer times at elevated temperatures during the Production heat treatment allow for significant grain growth at lower cold work amounts. In addition, grain growth is unavoidable for 30% cold work regardless of heating rate.
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