Fast differential scanning calorimetry to mimic additive manufacturing processing: specific heat capacity analysis of aluminium alloys.

Eutectic AlSi12, commonly used in casting and in additive manufacturing, is investigated with Fast Differential Scanning Calorimetry to determine the impact of different cooling rates from the liquid state upon the apparent specific heat capacity on subsequent heating. A heat flow correction strategy is developed and refined for the reliable and precise measurement of sample heat flow using chip sensors and assessed by the evaluation of results on pure (99.999%) aluminium. That strategy is then applied to the study of the AlSi12 eutectic alloy, and rate-dependent perturbations in the measured apparent specific heat capacity are discussed in terms of Si supersaturation and precipitation. Several cooling rates were implemented from - 100 to - 30,000 K s-1, and subsequent heating ranged from + 1000 to + 30,000 K s-1. After rapid cooling, a drop in AlSi12 apparent specific heat capacity is found on heating above ~ 400 °C; even at rates of + 10,000 K s-1, a result which has high relevance in metal additive manufacturing where similarly fast temperature cycles are involved. The Literature data, temperature modulated DSC and CALPHAD simulations on the heat capacity of AlSi12 are used to provide comparative context to the results from Fast Differential Scanning Calorimetry.

A Fast and Implantation-Free Sample Production Method for Large Scale Electron-Transparent Metallic Samples Destined for MEMS-Based In Situ S/TEM Experiments.

Microelectromechanical systems (MEMS) are currently supporting ground-breaking basic research in materials science and metallurgy as they allow in situ experiments on materials at the nanoscale within electron microscopes in a wide variety of different conditions such as extreme materials dynamics under ultrafast heating and quenching rates as well as in complex electro-chemical environments. Electron-transparent sample preparation for MEMS e-chips remains a challenge for this technology as the existing methodologies can introduce contaminants, thus disrupting the experiments and the analysis of results. Herein we introduce a methodology for simple and fast electron-transparent sample preparation for MEMS e-chips without significant contamination. The quality of the samples as well as their performance during a MEMS e-chip experiment in situ within an electron microscope are evaluated during a heat treatment of a crossover AlMgZn(Cu) alloy.