Question 4 A A Lead Tin Pb Sn Alloy Contains 64 Wt Proeutectic A And 36 Wt Eutectic I E A B At 183 C See 1 (37.74 KiB) Viewed 27 times
Question 4 A A Lead Tin Pb Sn Alloy Contains 64 Wt Proeutectic A And 36 Wt Eutectic I E A B At 183 C See 2 (49.99 KiB) Viewed 27 times
Question 4 (a) A lead-tin (Pb-Sn) alloy contains 64 wt% proeutectic a and 36 wt% eutectic (i.e., (a + B) at 183 °C. See Figure Q4 below for the Pb-Sn system. i. Calculate the average composition of this alloy just below the eutectic temperature. [6] ii. For this alloy, determine the relative amounts of a and 3 formed by the eutectic reaction. [6] T(°C) 300 200- TET 100 8 20 18.3 SECTION B L 40 Co 60 80 61.9 Co, wt% Sn Figure Q4 100 97.8 (b) A chain used to hoist heavy loads fails. Analysis performed on the failed link reveals considerable deformation and necking prior to failure. (i) What type of failure mechanism would you expect? (ii) Discuss briefly the possible reasons for failure. [2] [4]
(c) A 12.5 mm diameter metal bar with a 50 mm guage length is subjected to a tensile test. The following measurements were obtained. Determine the strain hardening coefficient. [7] Force (KN) 122 120 114 Gauge length (mm) 56.14 62.05 68.57 Diameter (mm) 12.19 11.60 11.03 Question 5 (a) Some pistons for automobile engines might be produced from a composite material containing small, hard silicon carbide particles in an aluminium matrix. i. Explain what benefits each material has in the composite may provide to the overall part. [6] ii. What problems might the different properties of the two materials cause in producing the part? [4] (b) How does grain size reduction influences the mechanical properties of materials. [4] (c) The strength of titanium is found to be 450 MN/m² when the grain size is 17x10 m and 565 MN/m² when the grain size is 0.8 x 106 m. Determine the constants in the Hall-Petch equation and i. [6] ii. [5] the strength of the titanium when the grain size is reduced to 0.2 x 10 m.
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