铅锡合金金属相图 .pdfVIP

MT4 Phase Diagram of Pb-Sn Alloys Name： SHI Tai Student Number 1. Purposes： 1. Define component, phase, diagram phase, and cooling curve. 2. Describe the phase change taking place at different point on a cooling curve. 3. Construct a diagram from cooling curves. 2. Instruments and specimens： Crucibles Thermoelectric couple Heating-furnace Multi-channel graph recorder Stirrer bar Specimens： Channel 0 1 2 3 4 5 Sn 100% 80% 62% 40% 10% -- Pn -- 20% 38% 60% 90% 100% 3. Introduction: A phase diagram is a plot of the equilibrium state of a system. A eutectic system can occur when terminal solid solutions exist on both end of the binary equilibrium phase diagram. In the Pb-Sn alloys system, there are two solid solutions-α and β. The α phase indicates a solid solution of tin in lead, whereas β presents in theopposite way. The eutectic invariant point appears at 61.9 wt% Sn. The maximum solid-state solubility both occur at 183℃ which is referred to as the eutectic temperature. At this temperature, there exists a point on the phase diagram (a single combination of composition and temperature) where three phases (the two solids and a solid) can exist simultaneously in equilibrium. This combination of temperature and composition is an invariant point on the binary diagram like the freezing point of water on the single component system the eutectic reaction where upon cooling L→α+βrepresents the isothermal transform