[Evaluation of material properties of in-service power plant components by Instrumented Indentation Method]

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Table of Contents

CHAPTER 1: INTRODUCTION3

Background of the study3

Problem Statement4

Aims & Objectives of the study5

Rationale of the study5

Significance of the study10

CHAPTER 2: LITERATURE REVIEW12

REFERENCES18

Chapter 1: Introduction

Background of the study

Al-Si family alloy was the most widely used aluminum alloy , it was widely used in the manufacturing of the engine parts of cars and aero spaces because of the high ratio of strength to weight . (Smith, 2002, pp 623-641) In sand mould casting, the silicon phases existed in the shape of needle or flake like, and the silicon phases sometimes were called secondary phase or strengthening phase . It was well-known that the best distribution of the silicon phases was that it was spotted everywhere and exhibited fine granules in Al alloy. So, many efforts should and could be done to strengthen the Al alloy and make it tougher. In order to make such a needle like phase finer and shorter, the permanent mould casting was adopted in producing Al alloy parts . (Fabio, 2010, pp. 79-98) In order to increase the cooling rate of the mould, prolong the mould life, enhance the producing efficiency, adjust the thermal balance of mould, improve the quality of parts, the cooling system was usually designed in the mould . Most of the Al-Si alloy parts were produced by permanent mould casting, including high pressure die casting, low pressure die casting, extruding die casting, gravity die casting, and so on . In order to make the Al-Si alloy stronger and tougher, some measurements were usually taken to refine the crystal granule (Zhang, 2008, pp. 107-111) to refine or round the secondary phase(Guohong, 2009, pp. 43-47 ), and thus enhanced the mechanical properties of the Al-Si alloy parts. Such mechanical properties as strength, rigid, hardness were determined by the character of Al-Si alloy microstructure . Metallographic experiments were the usually methods to observe and obtain the Al-Si alloy's microstructure . (Bonnet, 2004, pp45-61) The traditional way is that observing the microstructure under the microscope, then evaluating the microstructure contrasting to the standard metallographs. The results of those traditional methods are often subjective, and are different from the observers. They are also inaccurate, with low fidelity. (Leslie, 1981, pp. 35-65) Actually, the microstructure is not even and in order to obtain the character of the microstructure, a great deal of scopes should be observed and evaluated, the results should be statistically. With the developing of computer aided graphics and image processing technology, how to express the microstructure of Al-Si alloy in digital style became one of direction of the microstructure inspection advancing . (Dai, 2008, pp. 1559-1563) The principle of the digital expression was concluded concisely bellows: firstly, the images of microstructures were obtained by using advancing electronic and optic device instead of the human's eyes, then, with the aid of computer soft wares, the images were processed by computers instead of observers themselves, thirdly, the reports were written in digital style or graphs ...