GATE MT topic:metallurgy PYQs & Answers — Page 6

Questions 51–60 of 650. Imported answers require independent review unless marked reviewed.

Topic practice 650 questionsPage 6 of 65

For plane strain fracture toughness (K

) test of Maraging steel, the minimum thickness to achieve valid K

is (answer in integer) ____________ mm. (Given: K

= 90 MPa√m and yield stress = 900 MPa)

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The lattice parameter of Ni (face-centered cubic) is 0.35 nm and its shear modulus is 76 GPa. The strain energy per unit length of a screw dislocation in Ni crystal (rounded off to two decimal places) is ________ × 10⁻⁹ J/m.

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20 g of gold (Au) and 20 g of silver (Ag) are mixed to form a single-phase solid solution (assume ideal mixing). The atomic weight of Au is 197 g/mol and the atomic weight of Ag is 108 g/mol. The value of universal gas constant R is 8.314 J/mol-K. The total entropy of mixing (rounded off to two decimal places) is __________ J/K.

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2 moles of an ideal gas is reversibly expanded from 10 liter to 20 liter at isothermal condition. The value of universal gas constant R is 8.314 J/mol-K. If the temperature of the gas is 27 °C, the magnitude of work done in the process (rounded off to two decimal places) is ____________ Joules.

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Specific heat capacity at constant pressure (C

) of a solid metal is given by the following equation:

(in J/mol-K) = 20 + (5 × 10⁻³)·T (for T = 298 K to 1000 K)

At constant pressure, if the temperature (T in K) of 2 moles of metal is increased from 300 K to 600 K, the change in enthalpy of the metal (answer in integer) is __________ Joules.

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With reference to the Ellingham diagram, the standard Gibbs free energy change for the oxidation of solid metal M (s) and liquid metal M (l) is given below:

Reaction I:

M (s) + O₂ (g) → MO₂ (s)

ΔG° = (− 338900 − 15.2T lnT + 247T) Joules; from T = 300 K to melting point.

Reaction II:

M (l) + O₂ (g) → MO₂ (s)

ΔG° = (− 390800 − 15.2T lnT + 285.3T) Joules; from melting point to T = 1800 K

The melting point of the metal M (rounded off to one decimal place) is _____________ Kelvin.

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A given volume of liquid is undercooled just below the melting temperature to form a spherical solid nucleus (consider homogeneous nucleation). The Gibbs free energy of solidification (ΔGᵥ) is (− 0.5 × 10⁸) J/m³. The solid-liquid interfacial energy (γ) is isotropic and its value is 0.1 J/m².

The critical nucleus size for a stable nucleus is __________ nm (answer in integer).

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A 50 mm flat aluminum plate is reduced in thickness to 25 mm in a single pass cold-rolling operation with the rolling diameter of 1250 mm. For this case, the minimum required coefficient of friction between the plate and the roll (rounded off to two decimal places) is __________.

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A cylindrical furnace has 0.1 m inner diameter and 0.2 m height. Walls A₁ (inner section of cylindrical surface area) and A₂ (inner section of bottom surface area) are maintained at 1873 K. The sides and bottom are assumed to be black bodies, well insulated and heated electrically. The top area (A₃) is open to atmosphere maintained at 300 K, resulting in loss of heat ‘q̇’.

Given: View factors F₁₃ = 0.1175 and F₂₃ = 0.06, where Fᵢⱼ is the fraction of radiation leaving surface ‘i’ that is intercepted by surface ‘j’.

Stefan-Boltzman constant = 5.67 × 10⁻⁸ W/m²-K⁴

The power needed to maintain the furnace at 1873 K is (approximate to the nearest integer) _________________ W.

Diagram for Metallurgical Engineering question 59

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During carburizing of a steel, the surface concentration is kept constant at 1.4 wt.% carbon. Diffusivity of carbon for the steel at 950 °C is 6.25 × 10⁻¹¹ m²/s. At 950 °C, the time required to carburize the steel with an initial composition of 0.2 wt.% carbon to 0.859 wt.% carbon at a depth of 0.2 mm is ______________ seconds (approximate to the nearest integer).

Use the nearest value of the error function from the table given below for your calculation.

z	erf (z)
0.3	0.3268
0.4	0.4284
0.5	0.5205

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GATE MT topic:metallurgy PYQs

Question 51

Question 52

Question 53

Question 54

Question 55

Question 56

Question 57

Question 58

Question 59

Question 60