Question

Quostion 5 Alloy phase diagrams are useful in determining the freezing range of various metals and alloys. The binary phase diagram for Lead (Pb) Tin (Sn) is given below for the full compositional range. Of the compositions given, which is expected to have the lowest fluidity? (a) Pure Lead (Pb) [Owt% Sn] (b) 10wt% Sn (c) 20wt% Sn (d) 60wt% Sn (e) Pure Tin (Sn) [100wt% Sn] 400 327 °C 350 Liquidus Line Liquid 300 232 "C 250 aPb +L 200 aPb BSn+L Solidus Line 150 100 BSn I 50 Solid 40 0 (Pb) 60 80 100 20 Composition /wt % Sn (Sn) Temperature/C Question 24 Which of the following statements is NOT correct? (a) High chromium white cast irons can have a microstructure containing austenite dendrites surrounded by eutectic carbide and austenite.. (b) Forgeability is the capability of a material to undergo deformation during forging without cracking. (c) In general, ceramics have higher strength than metals. (d) Branched polymers typically have higher strength than linear polymers. (e) Low carbon alloy steels readily form martensite during quenching. Question 14 Which of the following is NOT correct? (a) Aluminium high pressure die castings are more prone to gravity segregation defects than aluminium sand castings (b) Squeeze casting is also known as liquid-metal forging because solidification occurs under high pressure, resulting in a fine microstructure with good mechanical properties. (c) Fine grain sizes result during semisolid metal forming because solidified dendrites are crushed into fine solids. (d) Columnar grain structures in sand castings can be suppressed by using heterogenous nucleation catalysts called grain refiners. (e) The lost wax casting method can produce intricate components from high melting point metals.

Answer 1

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