Papers by Keyword: Heat Treatment

Abstract: In this research work, Ni rich superelastic Nickel-Titanium(NiTinol) alloy rods were joined using a fully automated direct-driven rotary friction welding machine at 1900 rpm. Samples were subjected to heat treatment after the removal of flash bead. Corrosion behavior of the NiTinol samples were carried out using weight loss method and Potentiodynamic Polarization (PDP) technique using 3.5% NaCl and 1N HCl solution in interval of 12h, 24h, 36h, and 48h at different temperature conditions such as 25°C, 35°C, 45°C, and 55°C respectively. Research has been carried out to find the corrosion characteristics for both annealed and cryogenically treated samples. Research findings revealed that, in weight loss method the impact of corrosion has no effect in the welded zone. In PDP method, the corrosion rate is found to be less and insignificant compared to any other alloys. Hence, the material proved as anti-corrosive in nature. This fact is due to the formation of Titanium oxides (TiO₂) and Titanium nitrides passive layers which hinders the rate of corrosion. However, more corrosion resistance was seen in cryogenically treated welded samples compared to the other samples.

Abstract: The impact of heat treatment on the mechanical characteristics of aluminium metal matrix composite (MMC) was examined in this research work. Here the material chosen for matrix was Al7075-T6, which was aluminium alloy that was tempered with T6 configuration and the Al matrix was reinforced with Silicon nitride (Si₃N₄) powder. For the evaluation of mechanical properties totally two samples were fabricated, one was Al7075-T6 itself without any addition of any reinforcement and the other sample was composed of Al7075-T6 + 5% of Si₃N_4. These two samples were fabricated in necessary testing form with the help of stir casting technique. After fabrication and heat treatment of the samples the sample was mechanically tested to evaluate the tensile and impact strength of the samples prepared to find the changes in the mechanical properties due to the reinforcement of Si₃N₄ and due to the heat treatment process. The samples were subjected to heat treatment process at a temperature of around 500°C for 5 hours, after treating the samples with heat sudden quenching process was done by cooling with distilled water and artificial ageing process was conducted at 150°C for 24 hours. After all this process of fabrication and heat treatment the samples were analysed to find the mechanical properties.

Abstract: AZ91 magnesium injection molding is suitable for manufacturing complex-shaped electronic product frames or thin plates. However, the strengthening effect of the Mg₁₇Al₁₂ precipitate in AZ91 is limited, and it tends to dissolve during heat treatment, leading to a lack of particles that can pin grain boundaries and prevent grain growth. To address these challenges, the LAZ561Ca alloy has been developed, offering a reduced density (83% of AZ91), AlLi nanoprecipitates with strong strengthening capabilities, and thermally stable Ca-bearing intermetallics that effectively pin grain boundaries, maintaining a fine-grained structure (~8 μm) even after heat treatment. Experimental results demonstrate that AZ91 undergoes abnormal grain growth after solution treatment at 400°C due to a significant reduction in Zener pinning forces. In contrast, the LAZ561Ca alloy, with stable Al₂Ca precipitates, resists such growth during two-stage heat treatment at 370°C – 400°C. Through the coupling between Thermo-Calc and MICRESS software, multiphase field modeling reasonably reproduced the microstructure evolution during injection molding and heat treatment processes, highlighting its value in establishing digital physical metallurgy models. This study reveals the microstructural mechanisms of magnesium alloys, confirming the critical role of Ca-bearing precipitates in grain growth suppression. It provides a foundation for further optimization of alloy compositions and heat treatment conditions, paving the way for advanced magnesium alloys with enhanced performance in injection molding applications.

Abstract: This study investigates how heat treatment affects the mechanical properties and microstructure of extruded AA2017 aluminum alloy. Quenching (icy water vs. liquid nitrogen) and tempering (T6: 120–160°C; T7: 240°C) significantly alter hardness, tensile strength, and fatigue life. T6 promotes fine, coherent precipitates, enhancing strength and fatigue resistance, while T7 leads to over-aging and property degradation [X]. Icy water quenching improves fatigue life over liquid nitrogen by refining precipitates [Y]. Microstructural analysis reveals elastic adaptation (T6) and plastic shakedown (T7) as fatigue stabilization mechanisms, with fracture modes shifting from ductile (T6) to mixed ductile-brittle (T7) [Z]. These results optimize heat treatment for AA2017 in high-strength, fatigue-critical applications.

Abstract: This study assesses the impact of heat treatment on the microstructure and mechanical properties of AlSi10Mg alloy produced using the L-PBF method. The research compares the mechanical properties and microstructure of samples subjected to direct aging (heat treatment at 170 °C/2 h) and stress relief annealing (at 240 °C/2 h), which is below the temperature for silicon network decomposition. These results are then compared with the as-built state (without any heat treatment) after printing, serving as a reference. Tensile and hardness tests were used to determine the mechanical properties, while electron microscopy was employed to analyze the microstructure. The findings indicate that direct aging led to an increase in yield strength, tensile strength and hardness compared to the as-built state. In contrast, samples treated with stress-relief annealing exhibited comparable yield strength to the as-built state, but significantly lower tensile strength and reduced hardness. Notably, contrary to expectations, the ductility did not increase with decreasing strength and hardness; instead, it decreased.

Abstract: The 8-inch silicon carbide crystals prepared by physical vapor transport (PVT) offer a low-cost pathway for chip production, significantly enhancing the economies of scale. However, point defects， such as vacancies, interstitial atoms, and dislocated atoms produced by the temperature gradient mismatch and the fluctuation of the C/Si ratio during the growth process, seriously affect the residual stresses and the crystalline quality of the crystals. Using stress birefringence optical path difference and X-ray diffraction rocking curve detection methods, we characterized crystals annealed at different temperature. It is well-known that the residual stress of the wafer exhibits an uneven distribution, with the residual stress at the edge of the wafer significantly higher than that at the center. When the post-growth annealing temperature is below 2000°C, the residual stress of the crystal decreases rapidly due to the annihilation and transformation of point defects. However, when the temperature is increased further to 2200°C, a large number of irreparable and large-sized point defect clusters form, which severely degrade the crystalline quality of the crystal, induces lattice distortion, and lead to the generation of residual stress. Overall, the best residual stress relief is achieved at a post-growth annealing temperature of 2000°C.

Abstract: Ballistic steels are used for the basic ballistic protection of armoured vehicles against the compressive energy of exploding munitions and the impact energy of projectiles fired from small arms. Steels with hardness up to 500 HBW are used to protect the chassis of armoured vehicles. Steels with a hardness greater than 500 HBW are used to protect the cabs and turrets of armoured vehicles. Ballistic steels belong to the class of low alloy high strength steels where a good combination of high strength and toughness is required. Higher strength is achieved in the final production process which involves heat treatment by quenching and tempering. This treatment creates a martensitic structure. Another heat treatment option is the Q-P (quenching and partitioning) process, where higher material strengths can be achieved in some steels while maintaining ductility. This paper focuses on a comparison of the microstructure as observed using a light microscope of the ballistic steel Secure after heat treatment by the manufacturer and after heat treatment by the Q-P process. It was found that the Q-P process produces a finer grained structure and a change in mechanical properties due to the stabilised austenite and strained martensite in the microstructure of the ballistic steel.

Abstract: The article deals with the influence of process parameters on the properties of the protective coating deposited by Cold Spray technology on X52 pipeline steel. Part of the work is the evaluation of the effect of heat treatment on the resulting properties of the coating. Diamalloy 1003 powder was deposited on X52 steel substrate using four different process parameters, and then the samples were heat treated at 600°C, 800°C and 1000°C. The evaluation of results included analysis of microstructure, porosity and microhardness. The results show that heat treatment has a significant effect on the properties of the coating. The lowest porosity values for all tested parameters were achieved after heat treatment of 1000°C/1 hour.

Abstract: The article considers the features of heat treatment of steels, includes quenching, phase transformations and their influence on the structure and properties of the material. The key parameters of heat treatment are described: heating temperature, holding time and cooling rate, as well as their role in forming the required mechanical characteristics of steel. Phase diagrams are considered, in particular for the "iron-carbon" system, and their significance for choosing processing modes. Additional friction-strain hardening (AFSH) of various steel grades (20, 45, U7, U12) after preliminary quenching and low-temperature tempering is studied. An analysis of microstructural changes and microhardness of surface layers after AFSH is carried out, which confirmed the effectiveness of additional hardening. It was found that steels with a higher carbon content, limited to 0.8 %, demonstrate a greater depth of the hardened layer and higher microhardness values, which determines their feasibility for use in conditions of increased wear. The results of the study emphasize the importance of choosing the optimal AFSH mode depending on the carbon content in the steel, which has a significant impact on the formation of the strength characteristics of the material.

Abstract: A computer program in Python was developed based on the mathematical model, which allows obtaining preliminary calculations of the diffusion coefficient and nitriding time of a punch part. As a result of a numerical experiment, the process of nitrogen diffusion into the depth of the part was studied. The redistribution of nitrogen occurs as a result of diffusion due to the nitrogen concentration gradient in the volume of the part and the high quenching temperature. The numerical experiment confirms the full-scale experiment. Nitrogen penetration into the depth of the metal occurs precisely at the quenching temperature. The nitrogen content in the internal nitriding zone due to the nitrogen released from the surface layer increases and decreases on the surface with the exposure time of the part. Computer modeling and research of the diffusion coefficient in the process of heat treatment after ion nitriding made it possible to establish that for tool steels, diffusion along grain boundaries occurs. Thus, the use of complex ion nitriding (CIN), i.e. ion nitriding and subsequent heat treatment of nitrided parts allows you to change the phase composition and increase the depth of the nitrided layer due to nitrogen doping, control the nitrogen concentration and hardness along the depth of the nitrided layer due to selected modes.