In the present study, 18% Ni 300 maraging steel powder was processed using a selective laser melting (SLM) technique to study porosity variations, microstructure, and hardness using various process conditions, while maintaining a constant level of energy density. Nowadays, there is wide range of utilization of metal technologies and its products can obtain high relative density. A dilatometry study revealed that, through heating cycles, two solid-state effects took place, i.e., precipitation of intermetallic compounds and the reversion of martensite to austenite. During the cooling process, one reaction took place (i.e., martensitic transformation), which was confirmed by microstructure observation. The improvements in the Rockwell hardness of the analyzed material from 42 ± 2 to 52 ± 0.5 HRC was improved as a result of aging treatment at 480 °C for 5 h. The results revealed that the relative density increased using laser speed (340 mm/s), layer thickness (30 µm), and hatch distance (120 µm). Relative density was found approximately 99.3%. Knowledge about the influence of individual parameters in the SLM process on porosity will enable potential manufacturers to produce high quality components with desired properties.

Since the forming of the microstructure depends on the specific of the casting method, which directly affects further mechanical and physical properties of the material, it is important to understand how to control the microstructure of the cast to understand changes that taking place during the crystallisation process. For estimating the metallurgical quality of the liquid metal before casting, the thermal-derivative analysis (TDA) is utilised. The TDA has been used for a long time, in both ferrous and non-ferrous industries casting. The Universal Metallurgical Simulator and Analyser (UMSA) platform is a rapid, sensitive and economical method of determining a full range of solidification features. The work focuses on the thermal analysis and heat treatment of aluminium alloys. The liquidus and solidus temperatures and dendrite coherency point (DCP) are then characterised. The research shows that the UMSA platform allows precise determination and calculation of thermal parameters. The influence of the heat treatment on structure and properties of aluminium castings has been determined as well. Heat treatment was carried out to increase the mechanical properties of aluminium alloys. Based on the findings above, the influence of microstructure on properties of the alloys is discussed.

Dilatometric studies in 18-Ni steel components fabricated by selective laser melting technique were carried out to determine the influence of heating rate on transitions occurring during the heating cycle. SLM components have been examined in controlled heating and cooling cycles. For analysis, heating of the analysed materials was carried out at heating rates of 10, 15, 20, 30 and 60 °C min⁻¹. During the heating process, two solid-state reactions were identified—i.e. precipitation of intermetallic phases and the reversion of martensite to austenite. A simplified procedure based on the Kissinger equation was used to determine the activation energy of individual reactions. For precipitation of intermetallic phases, the activation energy was estimated 301 kJ mol⁻¹, while the martensite to austenite reversion was determined at the activation energy 478 kJ mol⁻¹.

The microstructure that is attributable from the distinct casting method dictates new engineering and physical attributes of the material. To understand how to manage the microstructure of the casts, it is necessary to comprehend the differences in microstructure through crystallisation. The effects of cooling rate (0.5, 0.9 and 2.1 °C s⁻¹) on the characteristic parameters of the evaluation of aluminium dendrites in Al–Mg alloy during solidification at different cooling rates were investigated by thermal derivative analysis. Because of the facts that castability is influenced significantly by the dendrite coherency point, which represents the time, temperature, and solid fraction at which interlocking solid network forms through solidification, an increment in the solid fraction at coherency can improve the casting attributes of the material and diminish casting defects. Castability of aluminium is defined with a new approach based on one thermocouple thermal analysis technique of fraction solid at a dendrite coherency point. Changes of sample linear dimensions and the coefficient of linear thermal expansion and diagrams of this coefficient as a temperature function during heating and cooling cycle of investigated materials were registered and presented. The analysis shows that the thermal interpretation is carried out on Universal Metallurgical Simulator and Analyzer device which is a useful instrument for the accumulation and calculation of thermal parameters. The manuscript provides to the better understanding non-equilibrium metallurgical characterisation of aluminium alloys.