Chapter five - DTA and heat-flux DSC measurements of alloy melting and freezing

Abstract

This chapter focuses on differential thermal analysis (DTA) and heat-flux differential scanning calorimetry (HF-DSC) of metals and alloys. A thermal analysis guide focused only on metals and alloys is appropriate because metals and alloys behave quite differently from molecular materials such as polymers and organics. Freezing and melting occur rapidly in response to changes in temperature compared to other materials. Melting and freezing transformations, once initiated, take place within, at most, a degree of local thermodynamic equilibrium. Therefore, the chapter also focuses on melting and solidification behavior because special methods can be employed that are not necessarily useful for a broader class of materials and processes. The chapter intends to provide the thermal analysis user with the considerations that are necessary for proper sample preparation and to illustrate how the sample characteristics influence the proper interpretation and analysis of measurements. The chapter describes different types of information usually sought from DTA/HF-DSC during the melting and freezing of alloys. The details of instruments, operation and calibration are described. The goal is to describe the thermal lags between the sample and sample thermocouple that must be understood to enable good analysis of data. The chapter also details the response of the DTA to binary and ternary alloys, respectively.