(20 Points) a) Jet engine turbine blades are usually made from single crystals o
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(20 Points) a) Jet engine turbine blades are usually made from single crystals of Nickel b) What composition of lead-tin solder is the best choice for joining electronic c) What are the different mechanisms of strengthening metals/alloys you have d) How does the microstructure help in predicting the mechanical properties of an 5. Answer the following superalloys. Explain citing the conditions of temperature and load? components? Why is this composition chosen? learnt in the class. Clearly describe the principle behind at least 3 of these alloy system? What are the different ways to tune the microstructure and hence the properties in such systems? Explain with examples.Explanation / Answer
5.)
a)
The single crystal structure has the ability to withstand creep at higher temperatures than crystalline turbine blades due to the lack of grain boundaries present. Grain boundaries are an area of the microstructure where many defects and failure mechanisms start which leads to creep occurring.
The lack of these grain boundaries inhibits creep from occurring in this way. Creep will still occur in single crystal turbine blades but due to different mechanisms that occur at higher temperatures. The single crystal turbine blade does not have grain boundaries along directions of axial stress which crystalline turbine blades do. This also works to increases the creep strength.
Within the single crystal of the superalloy, there are two phases present, a gamma matrix and a gamma prime precipitate. The gamma prime phase needs to be greater than 50% volume fraction in the superalloy to provide the increase in creep resistance. The presence of the gamma prime phase increases the mechanical strength of the turbine blade by preventing dislocation motion. The gamma prime phase has the unusual property of increasing strength as temperature increases.
b)
Alloys commonly used for electrical soldering are 60/40 Sn-Pb, which melts at 188 °C (370 °F),[10] and 63/37 Sn-Pb used principally in electrical/electronic work. 63/37 is a eutectic alloy of these metals, which:
c)
Reinforcing by Grain Size Reduction
This depends on the way that it is troublesome for a separation to go into another grain, particularly on the off chance that it is extremely misaligned. Nuclear confusion at the limit causes intermittence in slip planes. For high-edge grain limits, push at end of slip plane may trigger new disengagements in contiguous grains. Little edge grain limits are not powerful in blocking separations.
The better the grains, the bigger the territory of grain limits that hinders disengagement movement. Grain-estimate lessening as a rule enhancesstrength too. For the most part, the yield quality changes with grain estimate d as per:
sy = s0 + ky/d1/2
Grain size can be controlled by the rate of cementing and by plastic distortion.
Solid-Solution Strengthening
Including another component that goes into interstitial or substitutional positions in an answer builds quality. The polluting influence particles cause grid strain which can "stay" disengagements. This happens when the strain brought on by the alloying component remunerates that of the disengagement, along these lines accomplishing a condition of low potential vitality. It costs strain vitality for the separation to move far from this state (which resemble a potential well). The shortage of vitality at low temperatures is the reason slip is prevented.
Unadulterated metals are quite often milder than their compounds.
Strain Hardening
Pliable metals get to be more grounded when they are distorted plastically at temperatures well underneath the dissolving point (icy working). (This is not the same as hot working is the forming of materials at high temperatures where vast misshapening is conceivable.) Strain solidifying (work solidifying) is the purpose behind the versatile recuperation .
The purpose behind strain solidifying is that the separation thickness increments with plastic twisting (cool work) because of augmentation. The normal separation between disengagements then declines and disengagements begin obstructing the movement of every one.
The measure of strain solidifying is the percent icy work (%CW), given by the relative lessening of the first territory, A0 to the last esteem Ad :
%CW = 100 (A0–Ad)/A0
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