【導(dǎo)讀】材料特性是鑒別材料的基礎(chǔ)和用在逆向工程評(píng)估性能的一部分。說，只有當(dāng)兩種材料的特性被對(duì)比并找出相同點(diǎn)后，才可以評(píng)定他們是相同的。這樣的成本可能是非常高的，但在技術(shù)上的確是可行的。確定相關(guān)的材料特性和當(dāng)量需要全面的了解材料和這種材料制成的部分功。在逆向工程評(píng)估項(xiàng)目中，要想令人信服地解釋有關(guān)材料的性能、屬性、最終。本章的主要目的是討論和著重于在逆向工程中材料特性與機(jī)械冶金的應(yīng)用，力學(xué)性能是與當(dāng)用力時(shí)彈性和塑性的反應(yīng)有。物理化學(xué)性質(zhì)密切相關(guān)。當(dāng)退火的唯一目的是為減小壓力，該退火過程通常被稱為消除。固溶熱處理僅適用于合金，但不適用于純金屬。體，隨后迅速冷卻，以形成固溶體。固溶熱處理往往后續(xù)是老化處理以達(dá)到沉淀硬化。然而，楊氏系數(shù)通常也被稱為應(yīng)力和應(yīng)變之間的比率，它。與對(duì)應(yīng)的等軸晶粒對(duì)比，一個(gè)單一晶體的噴氣發(fā)動(dòng)機(jī)渦輪機(jī)翼

　　

【正文】 boiling point. For example, the melting temperature of pure iron is marked as 1,534176。 C in Figure . However, for binary alloys, where C = 2, the Gibbs’ phase rule allows one more independent variable. For a given position, the binary alloy has the liquid– solid phase transformation extended over a range of temperatures with a coexisting liquid and solid mixture, instead of at a fixed temperature. As shown in Figure , at 1,400176。 C, the Fe– 3% C binary alloy is in a homogeneous liquid state. It will start to solidify when the temperature decreases below the liquidus around 1,300176。 C. The liquidus is the temperature boundary in aphase diagram where the liquid starts to solidify. In other words, the liquidus is the locus of the starting melting temperatures of the alloys at various positions. In Figure , it is the curve that starts at 1,534176。 C where pure liquid iron melts, and continues to 1,147176。 C, the melting temperature of Fe– % C. The Fe– % C is defined as eutectic position. Despite that it is a binary alloy, it melts at a fixed temperature, 1,147176。 C, because two different solid phases solidified simultaneously. The eutectic temperature is the lowest melting temperature of ironcarbon alloys, as shown in Figure . The locus of the pletion temperature of solidification is defined as solidus. Above the liquidus the alloy is in a homogeneous liquid state, which is monly referred to as the liquid phase or liquid solution and labeled L in many phase diagrams. Below solidus the alloy is in a homogeneous solid state, which is often referred to as solid phase or solid solution. The various solid phases of an alloy are usually designated with Greek letters, starting with α from the left and usually continuing as β , χ , δ , ε , φ , γ , and η phases, as one moves to the right across the phase diagram. In a Fe– 3 %C alloy, the newly formed solid γ phase and the remaining liquid will 21 coexist between the liquidus and the solidus of 1,147176。 C. The Fe– 3% C alloy will be sequentially transformed into various solid phases, from γ to α mixed with Fe3C, as the temperature continuously decreases. Thus, a molten alloy will solidify from a homogeneous liquid state into a multiphase solid state。 each forms at consecutive steps during the solidification process. Quantitative analysis of each phase at a particular temperature can be conducted based on the Lever rule. The phase diagram illustrates these phase transformations, and provides invaluable “ footprints” allowing engineers to retrace the process the original part experienced in reverse engineering. The principles of thermodynamics can theoretically predict the existence of a phase in an equilibrium phase diagram. However, it might take infinite time to acplish the phase transformation. The rate and mechanism of forming this phase are guided by the principles of kiics, which also explain the many nonequilibrium phase transformations. A variety of nonequilibrium phase transformation diagrams are used for many engineering applications where the temperature change rate is intentionally controlled to create specific nonequilibrium phases. One example is the continuing cooling curves of ferrous alloys that are widely used in the heat treatment industry. From a reverse engineering perspective, these continuing cooling curves often provide more practical information than the equilibrium phase diagrams. Most engineering alloys contain more than two alloying elements. If there are three constituent elements, it is called a ternary system. The ternary phase diagram is a threedimensional space prism where the temperature axis is vertically built on top of the position triangle base plane, with each side representing one element. It is a space phase diagram with three binary phase diagrams, one on each side. grain Morphology Equivalency The three most monly observed grain morphologies of metal microstructure are equiaxed, columnar mixed with dendritic casting structure, and single crystal. In the equiaxed microstructure, shown in Figure , one grain has roughly equivalent dimensions in all axial directions. The columnar structure usually appears 22 in castings when the solidification process starts from a chilly mold surface and gradually moves inward to form a coarse columnar grain morphology. The columnar structure is usually mixed with a dendritic casting structure in the end. The single crystal has no adjacent grains and no grain boundaries。 the entire crystal aligns in one crystallographic direction. However, these basic grain morphologies will evolve into FIgurE Microstructure of a tungsten wire with elongated grain morphology. more plex configurations through kiic processes, for example, recrystallization and grain growth. Other derivative microstructures are the direct products of specific processes. For instance, cold or hot drawing can produce highly directionally textured microstructure with all the grains lined up in one direction. Figure shows the textured microstructure with high directionality of a tungsten wire. In reverse engineering it is crucial that the replicated part have grain morphology equivalent to that of the original part for the following two reasons. First and foremost, the material properties and part functional performance heavily depend on the microstructure. Second, the grain morphology provides critical information on the manufacturing process and heat treatment schedule. Parts showing different grain morphologies are made by different manufacturing processes with different heat treatments, and have different mechanical properties.