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Assignment6 - o C and causes the particles to coarsen...

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1 Assignment #6 ME264 Materials Science for Mechanical Engineering Spring 2009 Due Date: 08 April 2009 (4 pts) 1. (1pt) Explain what is meant by the ideal strength of a material. 2. (2pts) (a) A polycrystalline aluminum allot contains a dispersion of hard particles of diameter 10 -8 m and average center-to-center spacing of 6 x 10 -8 m measured in the slip planes. Estimate their contribution to the tensile yield strength, σ y , of the alloy. (b) The alloy is used for the compressor blades of a small turbine. Adiabatic heating raises the blade temperature to 150
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Unformatted text preview: o C, and causes the particles to coarsen slowly. After 1000 hours they have grown to a diameter of 3 x 10-8 m and are spaced 18 x 10-8 m apart. Estimate the drop in yield strength. (The shear modulus of aluminum is 26 GN m-2 , and b = 0.286 nm.) 3. (1pt) The yield stress of a sample of brass with a large grain size 20 MN m-2 . The yield stress of an otherwise identical sample with a grain size of 4 μ m was 120 MN m-2 . Why did the yield stress increase in this way? What is the value of β in equation (10.5) for the brass?...
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