Papers by Keyword: Thermal Cycle

Abstract: Due to tighter restrictions on the use of hazardous lead-bearing solder alloys, lead-free solder research has seen significant growth in recent years. The most common SAC alloys have emerged as viable candidates for the substitution of conventional Sn-Pb alloys among the representative lead-free solders (Sn-Cu, Sn-Bi, Sn-Zn, Sn-In, Sn-Ag, and Sn-Ag-Cu (SAC)). These alloys have limited use in contemporary microelectronic packaging devices due to various worries about the existence of brittle intermetallic compounds (IMCs) like Ag₃Sn and Cu₆Sn₅ in these materials. Over the years, numerous lead-free solder alloy alternatives with nanoparticle reinforcement have been proposed as an alternative to limit the growth of IMCs and enhance solder joint durability. This paper details the development of lead-free solders with selected fillers and reinforcements to date. The thermal cyclic test method was also discussed as one of the alternatives for reliability test techniques to be explored in future studies on this topic. In conclusion, fillers and reinforcements are also essential for enhancing interconnection’s heat cycle efficiency. Exploring various fillers and reinforcements that can be used to advance lead-free solder technology with thermal cyclic methods will open more investigation opportunities for lead-free solders.

Abstract: The main exploitation process of heavy oil is cyclic steam huff and puff. Cyclic operation causes cumulative damage to thermal recovery casing and causes a large number of failures. Failure analysis shows that the main failure factor of thermal recovery casing is the low cycle fatigue process caused by thermal cycle, which results in the decrease of strength of casing material, thus causing casing fracture and failure. Based on the failure analysis results, the low cycle fatigue tests of 80SH thermal recovery casing steel under different temperature, strain, pre-strain and other conditions were carried out. The influencing factors, life prediction model and criterion of service safety of casing materials under thermal recovery service conditions were first proposed, which provides a strong theoretical basis for the service safety design theory of thermal recovery casing materials. The research shows that the strain limit and low cycle fatigue life are the two core issues of service life. Life predictions need to satisfy two criteria. The first is the strain criterion. The strain limit should be lower than the total strain during the long service life. And the second is the low cycle fatigue criterion, which satisfies the expectation of low cycle fatigue life under double conditions of strain amplitude and mean strain.

Abstract: Effect of process parameters of microstructure formation and mechanical properties of direct laser deposited parts of cold-resistant steel 09CrNi2MoCu is studied. Due to local properties of buildup depends on thermal cycle during fabrication simulation of temperature field was carried out. The following cases were analysed: deposition of the first layer on massive substrate and deposition of a layer on the buildup far from the substrate. It was established that one time high temperature reheating of deposited layer has no effect on hardness while additional reheating up to lower temperature leads to considerable decrease in hardness by 87-100 HV. Far from substrate hardness and microstructure bands of 0.7-0.8 mm thickness have a hardness variation in the range of 250-300 HV. The area close to the substrate has a microstructure of upper bainite with higher hardness due to higher cooling rates during deposition. In the process of deposited, at a higher power, a quick process of heating and cooling occurs, and vice versa, which forms various products of bainite transformation. From the obtained modes were presented the results of tests for impact strength at low temperatures.

Abstract: The shape of the parts, created by the technology of direct laser metal deposition (DLMD), is influenced by various parameters, for example, the power and diameter of the laser source spot. The contribution of energy from the laser affects the temperature distribution in the formed layers. The changing temperature in the working area entails a change in the geometry of the layers and affects the stability of the process. In this paper, experiments on the measurement of temperature cycles in the DLMD process with different directions of the filling track are carried out. An infrared camera was used to measure thermal cycles. The correspondence table between the intensity of thermal radiation of the material and the absolute temperature was developed. The experiments are carried out with the filler material 316L. The effect of the maximum temperature on the layer height is shown, and thermal cycles in the formation of layers for different filling strategies are presented.

Abstract: It is known that heat treatment (HT) highly affects the properties of base metal (BM) and fusion zones (FZ) of duplex stainless steel (DSS). In fact, it may give unwanted structure changes. Duplex stainless steels SAF 2205 welded joint was subjected to thermal cycle at temperature of 850^◦C at holding times 1, 3, 5 and 7 hours. The influence of heating cycles and concentration of corrosive medium on the corrosion properties and microstructure of 2205 alloy was the objective of this work. It was found that process led to noticeable decrease in the corrosion resistance of BM and FZ specimens; moreover the decrease was large in BM than FZ. It was also found that sigma phase (σ) precipitated in the different zones of the structure. σ phase volume fraction was found to increase with increasing the holding time of HT, and its increase is larger in BM. Corrosion resistance was found to be oppositely related to σ phase formation. Secondary austenite phase (γ₂) was also precipitated and its volume fraction in FZ was found to increase with increasing the holding time of HT and decreased in BM.

Abstract: The paper describes thermal and deformation effects of weld surfacing on properties of deposited metal for high-speed tools. The technological process, enabling optimal conditions for producing of deposited metal with high mechanical properties and quality, which significantly increases working capacity of welded parts, is given.

Abstract: The additive manufacturing of titanium parts by laser metal deposition (LMD) offers a promising alternative to conventional machining of aviation parts. The technology enables the production of near net shape parts with higher deposition rates than powder bed-based processes. Ti-6Al-4V powder is fed directly into a high-power laser beam in order to form a deposition track on the underlying material. For three dimensional parts several tracks are stacked on top of each other. In this paper the material evolution from powder to a solid wall during LMD is investigated. Powder properties as well as the microstructure in deposited structures are thoroughly described and analyzed. The gained knowledge provides a deeper process comprehension and is an important step towards high-quality additive manufacturing of Ti-6Al-4V. At first, the influence of powder particle size on the LMD process is quantified by creating two powder fractions with different sieving procedures. The used material is recycled Ti-6Al-4V powder from a powder bed-based AM process with particle sizes up to 150 µm. The powder is characterized according to current standards; apparent density, tap density and the flowability are determined as well as the particle size distribution. Additionally, the particle morphology is analyzed using electron beam microscopy. In order to link the powder properties to the LMD process and to identify impact factors to the feeding behavior the mass flow of both powder fractions is measured. Secondly, walls are manufactured with the characterized powder and the resulting microstructure is analyzed. Because of the layer-wise deposition and the resultant periodic heat input each layer experiences several thermal cycles. As a result various solid phase transformations occur during the deposition of consecutive tracks. In addition the thermal boundary conditions change with increasing wall height and a heterogeneous microstructure is observed. It consists of non-equilibrium phases (martensitic or massive α) and α+β lamellae. Based on an existing numerical model the thermal history of each layer is estimated and an explanation is presented for the complex sequence of solid phase transformations in each area of the structure.

Abstract: The goal of this study is to identify LaCo_0.6Ni_0.4O_3-δ (LCN) as reliable cathode contact material for intermediate temperature solid oxide fuel cells (SOFC). LCN was prepared through the polymeric steric entrapment precursor route and calcined at 800 °C which shows single perovskite phase. Area specific resistance (ASR) of LCN was measured at 750 °C. The investigation shows that the ASR can be maintained about 50 mΩ·cm² for 100 hours operation, and presented ASR stability within 10th thermal cycles. The excellent performance of LCN is attributed to good interface adhesion between LCN and interconnect alloy.

Abstract: The power saving and energy-saving control plays a crucial role in green building design. An intelligent electricity and heat saving control method is proposed based on PID control optimization control, this algorithm is applied in the design of green building, the collection of data is taken with feedback processing, the design method of energy saving and heat savingcontrol unit is presented in intelligent building, it provides the accurate basis for energy-saving and heat saving cycle control optimization design. The application of energy circulation control in design of green buildings is realized. The four layers real building is taken as the subjects in the experiment, the experimental results show that, the controller is applied in energy saving control of green building, it can effectively improve the control accuracy.

Abstract: In the paper criteria of thermal cycle parameterization for surfacing of metallurgical equipment parts with heat-resistant steels are proposed.