DIAGRAMA DE FASES ( ALEACIÓN BINARIA CON EUTÉCTICO)

Explanation of Binary Phase Diagram

In this section, the speaker introduces a binary phase diagram, which represents the phases and areas of a binary alloy composed of two metals. The diagram shows the temperature axis on the y-axis and explains the concepts of liquidus line, solidus line, and eutectic composition.

Understanding the Binary Phase Diagram

• The binary phase diagram consists of four main areas.

• The y-axis represents temperature, with the melting temperature indicated at the top.

• The liquidus line represents the range of temperatures where both metals are completely miscible in their liquid state.

• The solidus line represents the range of temperatures where both metals are insoluble in their solid state.

• The eutectic composition is a specific composition formed by alternating crystals of metal A and metal B.

Phases in Different Areas

This section explores different areas within the binary phase diagram and describes the phases present in each area.

Phases in Upper Area (Liquid + Crystals)

• In the upper area above the authentic line, there is only one phase consisting of a mixture of liquid and crystals.

• This occurs because both metals are soluble in their liquid state.

Phases Below Liquidus Line

• As we move below the liquidus line, two phases start to appear.

• One phase is a mixture of liquid and small crystals of metal B.

• The other phase is composed mainly of metal A crystals.

Phases Below Eutectic Composition

• Further below, we find an area where there is a mixture of eutectic composition and metal A crystals.

• At this point, we have reached eutectic composition plus crystal formation.

Microstructures in the Binary Phase Diagram

This section discusses how microstructures are represented in the binary phase diagram and provides visual examples.

Representation of Microstructures

• In the upper part of the liquidus line, there is a single-phase consisting of liquid metal.

• As we move downwards, smaller crystals of metal A start to form within the liquid.

• At the eutectic composition point, there is an alternating structure of metal A and metal B layers.

Example Calculation

The speaker presents an example calculation using a binary alloy with specific melting temperatures and solubility characteristics.

Example Calculation for Different Temperatures

• Given two metals with melting temperatures of 350°C and 520°C respectively.

• The metals are soluble in their liquid state and insoluble in their solid state.

• An eutectic alloy contains 40% metal B at a temperature of approximately 150°C.

• The task is to determine the phases, proportions, and compositions at different temperatures (450°C, 350°C, 250°C, 150°C, and 50°C).

Due to limited information provided in the transcript, further details about the example calculation are not available.

New Section

This section discusses the composition of a liquid and the formation of crystals at different temperatures.

Composition of the Liquid

• The liquid has a composition of 77.3% B and 27% A.

• At approximately 350 degrees Celsius, the first crystals start to form in the liquid. The composition of the liquid remains at 73% B and 27% A.

Coexistence of Two Phases

• At this point, there are two phases present: a liquid phase and crystal phase.

• The composition of the liquid phase is approximately 56% B and 44% A, while the crystal phase is formed by crystals with the same composition as before (73% B and 27% A).

Percentages of Each Phase

• Using the lever rule, we can determine the percentages of each phase.

• The percentage of solid phase is calculated as (73 - 56) / (73 - 56 + 100 - 56) = 38.8%.

• Therefore, the percentage of liquid phase is complemented to be approximately 61.2%.

New Section

This section explores what happens when reaching point four on the diagram.

Disappearance of Liquid Phase

• At point four, located on the solid line at around 150 degrees Celsius, there is no longer any liquid present.

• The solid phase has a composition of 73% B and 27% A.

New Section

This section discusses compositions when only crystals are present.

Composition without Liquid

• When there is no liquid, the composition of the solid phase is 73% B and 27% A.

Composition with Authentic Crystals

• At point five, at 50 degrees Celsius, the composition of the crystals is a mixture of authentic crystals and crystal B.

• The composition of the authentic crystals remains the same as before (40% B and 60% A).

• The composition of crystal B is not mentioned in the transcript.

Conclusion

The transcript discusses the composition changes in a liquid and the formation of crystals at different temperatures. It explains how to determine the percentages of each phase using the lever rule. Additionally, it explores what happens when reaching points four and five on the diagram.