1.A polycrystalline Al alloy contains a dispersion of hard particlesof diameter 10-8m and average center to center spacingof 6x10-8m measured in the slip planes. Estimatetheir contribution to the tensile yield strength,σy, of the alloy.
2.The alloy is used for the compressor blades of a smallturbine. Adiabatic heating raises the blade temperature to150 degrees C, ans causes the particles to coarsen slowly. After 1000 hours they have grown to a diameter of 3 x10-8m ad are spaced 18x10-8 m apart. Estimate the drop in yield strength (the shear modulus of Al is26GNm -2 , and b is 0.286nm.
3.Yield stress of sample of brass with large grain size was20MNm-2. The yield stress of an otherwiseidentical sample with grain size of 4micrometer was 120MNm-2. Why did the yield stress increase in thisway? What is the value of β in equation [ τy = (FgbG/α)1/2 d-1/2 =βd-1/2] for the brass?
4.Estimate the tensile strength of the wire and the work required totake 1m3 of the wire to the point of necking