(c) Describe and explain the change of the two energies during solidification transformalion.(4%)

4. Consider the impurity diffusion of phosphorus into a silicon wafer. If phosphorus is diffused into a thick silicon waler with no previous phosphorus in it at a temperature of 1100℃. If the surface concentr tration of the phosphorus is 1 x atoms/cm3and its eoncentration at ce of 1.2 Jum below the surface is atoms/cm3, how long must be required for the impurity diffusion? The difiusion coeficient for phosphorus diffusing in silicon at 1 100*C is 3.0 x. (10%) 

(a) Estimate the engincering strain just before yield. (3%)

(b) What is the corresponding true strain just before yield? (3%)

(e) Determine the true stress corresponding to the engineering ultimate tensile strength. (3%)

(d) Determine the true strain just before fracture. (3%)

(a) the degree of deformation (3%)

(b) the initial grain sizc (3%)

(c) the purity of the metal (3%)

(a) Describe the austempering process for a plain-carbon steel. (4%)

(b) Draw an isothermal transformation diagram with a cooling curve for an austem mpered austenitized eutectoid plain-carbon steel. (4%)

110年 - 110 國立臺北科技大學_碩士班招生考試_材料科學與工程研究所：材料科學與工程導論#108255