Residual Properties Research Articles

Assessment of Lignin Residues from Bioethanol Production of Olive Stones as Green Chemical Thickener of Epoxidized Linseed Oil

This work focused on the characterization of lignin residues from bioethanol production of olive stones (OS) and the use of these residues to chemically thicken epoxidized linseed oil (ELO). OS were processed by an acid/steam explosion pretreatment, followed by pre-saccharification, using different enzyme dosages, and simultaneous saccharification and fermentation. The chemical composition of the OS lignin residues was analysed, revealing a high lignin content (66.6–69.5%), and lower quantities of glucan (17.4–19.3%) and xylan (2.8–2.9%). Whereas, the structural properties of OS lignin residues were characterized by Fourier-transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), thermogravimetric analysis and size exclusion chromatography (SEC). OS lignin residues displayed the main inter-unit linkages (β–β′ resinol (51.0–59.0%), followed by β-O-4′ alkyl aryl ethers (27.0–35.2%) and β-5′ phenylcoumaran (11.4–13.2%) substructures), high molecular weights (22,000–25900 Da), low S/G ratios (1.2–1.5) and phenolic groups content (48–55 mg GAE/g lignin). Moreover, OS lignin residues were dispersed in ELO to obtain thickened formulations, which were characterized by FTIR and NMR. Oil thickening was achieved by promoting the chemical crosslinking between lignocellulose hydroxyl groups and ELO epoxy groups, enabling the compatibilization of both components. Up to tenfold viscosity increment of the resulting thickened formulations in relation to ELO’s viscosity was observed. Besides, thickened formulations exhibited viscoelastic properties, evincing oil structuration to some extent.Graphical

Application of metaheuristic algorithms for compressive strength prediction of steel fiber reinforced concrete exposed to high temperatures

The demand for steel fiber-reinforced concrete (SFRC) in construction has surged, particularly due to its enhanced fire resistance, leading to extensive research on its residual properties after elevated temperature exposure. However, conducting experimental tests can be a time-consuming process, demanding significant resources in terms of time, cost, and human resources. In contrast, machine learning (ML) models can rapidly simulate outcomes, enabling researchers to explore a wide range of scenarios efficiently. The previous literature studies used either ensemble or individual models; however, this study made a unique approach to utilize hybrid models, which are more precise compared to the other types of ML models. Accordingly, a data-rich framework containing 304 data samples was utilized in this study to develop an efficient and robust predictive model for the compressive strength (CS) of SFRC at higher temperatures. Support vector regression (SVR) in combination with three distinct optimization algorithms, specifically, particle swarm optimization (PSO), the firefly algorithm (FFA), and grey wolf optimization (GWO) were utilized to develop the hybrid models. In addition, typical ML techniques such as random forest (RF) and decision tree (DT) were used for comparative analysis. Among the five models, the SVR-FFA hybrid model showcased superior predictive accuracy, with the SVR-GWO model following closely. The correlation coefficients (R) for both models exceeded 0.99. The SVR-FFA model demonstrated relative root mean square error (RMSE) and mean absolute error (MAE) values of 0.0375 and 0.0248, respectively, while the SVR-GWO model exhibited corresponding values of 6.0560 and 5.1326. The SHapley Additive exPlanation (SHAP) technique revealed that the influence of temperature is more significant compared to the heating rate. Moreover, a considerable enhancement was observed in CS as the steel fiber volume fraction (Vf) reached 1.5%; on the other hand, no further improvement was noticed when Vf exceeded the 1.5% threshold. The proposed hybrid models are robust and accurate methods to estimate the CS of SFRC in field applications.

Residual mechanical properties of high strength concrete BBR9 subjected to dynamic uniaxial compressive loading

In recent years, enormous efforts have been devoted to accurately quantifying the residual load-bearing capacity of concrete at the material level when exposed to elevated temperatures. However, relatively less attention has been given to investigating the effects of dynamic events such as terrorist attacks, earthquakes, and hurricanes, which can cause complete collapse of concrete structures and have significant public and economic consequences. Hence, in the present study, a modified Kolsky compression bar system integrated with a momentum trapping technique was implemented to develop precisely controlled pre-/post peak high strain-rate loading to introduce distinctive states of damage inside the high strength concrete HSC-BBR9 specimens and to measure the corresponding plastic strain. Thereafter, the partially damaged specimens were tested to quantify the residual mechanical properties (e.g., residual stiffness and residual strength) at different plastic strain levels. Furthermore, a high-resolution laboratory micro-CT scanner was used to visualize the 3D crack network morphology in the partially damaged specimens. The findings demonstrated a remarkable decrease in the residual capacity with increasing levels of damage-induced plastic deformation. Additionally, the results showed a fundamental difference in the influence of internal damage on residual stiffness and strength to be acknowledged in the formulations of future constitutive damage models for concrete materials.

Assessment of Residual Stress Behavior and Material Properties in Steels Produced via Oxynitrocarburized Metal Injection Molding

Assessment of Residual Stress Behavior and Material Properties in Steels Produced via Oxynitrocarburized Metal Injection Molding

Investigation on Residual Mechanical Properties of Galvanized Iron Cold-Formed Steel Sections Exposed to Elevated Temperatures

Cold-formed steel (CFS) sections are used to construct medium and low-rise structures designed to carry small-scale loads. CFS sections are manufactured without the application of heat. Therefore, it is crucial to comprehend the properties of CFS sections which are exposed to fire or elevated temperatures. To simulate the real- time fire exposure, an ISO Standard fire curve was used to heat the CFS sections. The objective of the study is to assess the residual mechanical strength of exposed sections after the elevated temperature test. The study aims to compile data for forecasting the degeneration of elements and to ascertain whether the structural components can be reused or replaced. The CFS sections were subjected to different temperatures, and after heating, two cooling methods were used to bring down to room temperature. The characteristics of the retrieved specimens, taken from exposed CFS sections were assessed using a tensile coupon test. The residual properties such as ultimate strength, yield strength, and elastic modulus were examined and reported. The influence of heating and cooling is more pronounced from the test results. A reduction in the yield and ultimate strength was noticed, and it was found to decrease as the heating intensity increases for air and water cooling respectively. In the case of yield and ultimate strength, the strength reduction is critical beyond 60 minutes. The elastic modulus was also found to be reducing with a similar trend. Based on the test results, reduction factors are proposed for ultimate strength, yield strength and elastic modulus. Reduction factors obtained for yield strength under 60 minutes of heating for air and water cooling is 0.575 and 0.557 respectively. In 120 minutes, the values are 0.400 and 0.329. Reduction factors obtained for ultimate strength under 60 minutes of heating for air and water cooling is 0.586 and 0.566 respectively. For 120 minutes, the values are 0.331 and 0.313.

Plant nutrient removal and soil residual chemical properties as impacted by maize planting date and density.

This study aimed to measure maize (Zea mays) plant nutrient content and nutrient removal in grain, and to evaluate the residual soil nitrogen, phosphorus, and potassium as impacted by planting date and density. Field experiments were conducted to evaluate six plant densities and seven planting dates using a split-split plot design with three replications. Besides the crop growth and yield parameters, six plants were collected at the maturity and soil was sampled from each plot for nutrient analysis. Plant N, P, and K concentrations varied with planting date and density and within the ranges of 0.6-1.024%, 0.054-0.127%, and 0.75-1.71%, respectively. Grain N, P, and K concentrations decreased with plant density and varied from 1.059 to 1.558%, 0.20 to 0.319%, and 0.29 to 0.43%, respectively. Soil residual nutrient varied with depth, planting density and date. Residual N concentration in the topsoil varied from 0.6 to 37.2 mg kg-1 in 2019 and from 1.5 to 11.2 mg kg-1 in 2020 and was high under the last two planting dates. Soil residual N concentration was higher in the second layer than in the topsoil. The N concentration in the third layer varied from 0.1 to 33.2 mg kg-1 and was impacted by plant density. Topsoil P did not vary among planting dates and densities. The second and third soil layers P concentration was not affected. There was 83% increase in topsoil K in 2020 compared to 2019, and a decrease of 65 and 23% in soil K was observed in the second and third soil layers, respectively. For maize production system sustainability, future research should use a holistic approach investigating the impact of planting date, plant density on crop growth, yield, nutrient uptake and remobilization, and soil properties under different fertilizer rates to develop the fertilizer recommendation for maize while reducing the environmental impact of the production system.

Practical strategies of phosphorus reclamation from sewage sludge after different thermal processing: Insights into phosphorus transformation

In the context of circular economy and global shortage of phosphorus (P) fertilizer production, it is crucial to effectively recover P during the treatment and disposal of sewage sludge (SS). Although thermal treatment of SS has been widely applied, a targeted P reclamation route is not yet well established. This study has comprehensively investigated and compared the physicochemical properties of SS and solid residues (hydrochar (HC), biochar (BC), sewage sludge ash (SSA), hydrochar ash (HCA), and biochar ash (BCA)) after application of three typical thermal treatment techniques (i.e., hydrothermal carbonization (180‒240 °C), pyrolysis (400‒600 °C) and combustion (850 ℃). P speciation and transformation during thermal processes were extensively explored followed by a rational proposal of effective P reclamation routes. Specifically, thermal processing decomposed organic P and converted non-apatite P to apatite P. Orthophosphate-P was found to be the main species in all samples. Physicochemical properties of the resulting thermal-derived products were significantly affected by the thermal techniques applied, thereby determining their feasibility for different P reclamation purposes. In particular, ash is not recommended for agricultural use due to higher harmful metals content, while acid leaching can be an alternative solution to synthesize non-Fe-containing P products because of the lower co-dissolved Fe content in the leachate. HC and BC offer the option for synthesis of Fe containing products. Eventually, HC and BC demonstrate great potential for agriculture application, however, a comprehensive risk assessment should be conducted before their real-world applications.

Investigation on reducing residual stress and optimizing performance of 2219 aluminum alloy friction stir welded joint by cold spraying

In this paper, the cold spraying (CS) was applied on friction stir welded 2219 aluminum alloy joint to reduce its residual stress. The correlation between the process parameters of CS and residual stress and mechanical properties was studied. Results reveal that the grain size of cold sprayed joints is significantly refined comparing to that of the welded joints, meanwhile the content of high angle grain boundaries and recrystallized grains increases. Cu powder has the best effect on enhancing the mechanical properties of joint. With the increase of gas pressure, the residual stress is decreased. The optimal powder type, gas pressure and gas temperature of CS are Cu powder, 3 MPa and 400 °C, respectively. The maximum residual stress is reduced from a tensile stress of 159 MPa in the welded joint to a compressive stress of −17.4 MPa in cold sprayed joint, and the tensile strength and elongation are further increased to 331 MPa and 4.6 %, respectively.

The role of Si in enhancing the stability of residual austenite and mechanical properties of a medium carbon bainitic steel

In this work, two bainitic steels with medium carbon content were developed by adding different Si. The mechanical properties of the two test steels and the stability of their retained austenite were studied, and the influence of Si in the steels was discussed. The results show that the film-like retained austenite of the high Si bainitic steel is greatly increased compared with that of the low Si bainitic steel and that the C content is increased, effectively preventing crack propagation and significantly improving the comprehensive mechanical properties. Due to the different Si content in the test steels, the orientation relationship of austenite in the steels has changed, and when the Si content is increased from 0.7 wt% to 1.4 wt%, the variant selection of bainite becomes weaker. Moreover, the increase of Si content not only inhibits the precipitation of carbides but also promotes the accumulation of C in the austenite, which improves the stability of the retained austenite.

The role of supplementary cementitious materials and fiber reinforcements in enhancing the sulfate attack resistance of SCC/ECC composite systems

The purpose of this study is to investigate the effects of sulfate exposure on the mechanical behavior of fresh-to-fresh composite systems (CS), incorporating self-compacting concrete (SCC) in compression and engineered cementitious composites (ECC) in tension. ECCs were designed based on various supplementary cementitious materials (SCM) such as low and high calcium fly ash, slag and reinforcing fibers such as PVA and steel fibers. Repeated cycles of immersion in concentrated sodium sulfate solution were followed by drying at high temperatures (80 °C). After 90 and 180 days of cyclic exposure, the mechanical properties including flexural, compressive and tensile bond strength and mass change were evaluated. To investigate microstructural deterioration and reaction product concentration, SEM-EDS and backscattered electron imaging were used to examine sulfate profiles at the interfacial zone between SCC and ECC. Composite samples demonstrated excellent physico-mechanical resilience. The incorporation of low calcium fly ash and slag was observed to have a beneficial impact on residual mechanical properties in long-term exposures, along with the de-passivation capacity of the reinforcing fibers. No physical de-bonding was observed in any CS, however phase assemblages revealed high concentrations of reaction products in the SCC layers near the interfacial bond with the ECC layers.

Post-creep residual tensile properties of multi-walled carbon nanotube/epoxy nanocomposites

Epoxy resin as a thermoset polymer is vulnerable to creep loading even at room temperature due to its viscoelastic nature. This study investigated the effect of reinforcing epoxy resin with different functionalized multi-walled carbon nanotubes (MWCNT) contents on the creep response and post-creep residual tensile properties of nanocomposites. The creep tests were performed on the nanocomposite specimens containing different filler contents and the neat epoxy specimen at 40°C under a constant load level of 200 N. It was found that the nanocomposites containing 0.3 wt% MWCNTs experienced 29.6%, 69.1%, and 74.1% decreases in the elastic strain, creep strain, and steady-state creep strain rate, respectively, compared to the neat epoxy. Furthermore, the tensile strength and stiffness of the neat epoxy and nanocomposite specimens were evaluated before and after a partial creep test (at a load level of 200 N for 150 min) by conducting tensile tests. The nanocomposites containing 0.3 wt% MWCNTs demonstrated considerable improvements of 35.9%, 41.2%, 27.9%, and 28.1% in strength, residual strength, stiffness, and residual stiffness, respectively, compared to the neat epoxy. Furthermore, scanning electron microscopy assessment was utilized to investigate the fracture surfaces of the nanocomposite specimens.

Test Research on Residual Mechanical Properties of Fiber-Reinforced Concrete Segments after High Temperature.

In order to research the residual mechanical properties of concrete shield tunnel segments after exposure to high temperatures, two types of concrete segments were designed: a self-compacting concrete segment and a mixed fiber (steel fiber and polypropylene fiber) self-compacting concrete segment. The mechanical properties of seven blocks of concrete segments (five segments after high-temperature exposure and two segments at room temperature) were tested to analyze the influence of different loading sizes and fibers on the development of cracks after high temperature, failure mode, crack width, deformation, and so on in the concrete segments. The results showed that the damage model of the segment after exposure to high temperature and the segment at room temperature were crushed in the pressurized zone, but the high temperature had little effect on the concrete in the pressurized area. The size of the preload at high temperatures had little effect on the remaining load capacity, and the effect on the number of cracks was mainly concentrated on the internal arc surface of the segment. After high-temperature exposure, the number of cracks on the sides and inner arc surface of the segment increased, and the development of cracks was concentrated as several major cracks at high temperatures. When fibers were incorporated, the cracks in the segment became obvious, where the cracks at the loading point became denser and the interval distance became smaller.

Investigation on the residual mechanical properties of glulam after exposure to elevated temperature

For structures that experience a fire event without collapse, determination of the residual capacity is required. The objective of this research is to determine the residual properties of glued laminated (glulam) timber after exposure to elevated temperature to enable post-fire structural evaluation. The residual compressive and shear properties of glulam were experimentally measured after exposure to a range of elevated temperatures (50, 100, 150, 200 and 250 ℃), considering also the effect of heating duration (30, 60 and 90 min) and cooling method (air cooling and water cooling). To account for transient temperature gradients, an effective temperature of the specimen was defined based on the dynamic time-temperature profile. For parallel-to-grain compressive strength, the reduction in residual strength remains within 20% of the initial strength as long as the effective temperature has not exceeded 170 ℃, but it drops severely to exceed 50% at 210 ℃. For shear strength, the permanent reduction is also within 20% after exposure to effective temperature lower than 190 ℃ and air cooling. Water-cooling leads to greater permanent reduction of mechanical properties compared with air-cooling. After first temperature exposure, additional cycles of heating-cooling (by air) do not further degrade the properties. Based on the test results, predictive formulae are proposed for the residual mechanical properties of glulam.

Using protein language models for protein interaction hot spot prediction with limited data.

Protein language models, inspired by the success of large language models in deciphering human language, have emerged as powerful tools for unraveling the intricate code of life inscribed within protein sequences. They have gained significant attention for their promising applications across various areas, including the sequence-based prediction of secondary and tertiary protein structure, the discovery of new functional protein sequences/folds, and the assessment of mutational impact on protein fitness. However, their utility in learning to predict protein residue properties based on scant datasets, such as protein-protein interaction (PPI)-hotspots whose mutations significantly impair PPIs, remained unclear. Here, we explore the feasibility of using protein language-learned representations as features for machine learning to predict PPI-hotspots using a dataset containing 414 experimentally confirmed PPI-hotspots and 504 PPI-nonhot spots. Our findings showcase the capacity of unsupervised learning with protein language models in capturing critical functional attributes of protein residues derived from the evolutionary information encoded within amino acid sequences. We show that methods relying on protein language models can compete with methods employing sequence and structure-based features to predict PPI-hotspots from the free protein structure. We observed an optimal number of features for model precision, suggesting a balance between information and overfitting. This study underscores the potential of transformer-based protein language models to extract critical knowledge from sparse datasets, exemplified here by the challenging realm of predicting PPI-hotspots. These models offer a cost-effective and time-efficient alternative to traditional experimental methods for predicting certain residue properties. However, the challenge of explaining why specific features are important for determining certain residue properties remains.

Short-term oxidation and residual compression properties of needle-punched carbon/carbon composites

Needle-punched carbon/carbon (NP C/C) composite is widely used in rocket-engine nozzles and re-entry vehicles. Recyclable technology expedited the research on repeated oxidation and residual mechaincal properties of thermal-protection materials. In this study, the critical longitudinal compression strengths before and after oxidation are derived based on the Timoshenko beam theory. Three repetitions of short-term oxidation cycles and compression experiments are investigated. The average oxidation rate of this composite was 5∼6% in 10 min and kept linear increase. In-plane and out-of-plane compressive strengths of NP C/C composite diminish quasi-linearly due to oxidation at 1000°C, with their moduli decreasing in a periodically slow-sharp pattern. After three oxidation cycles, the levels of residual in-plane modulus and strength were 55.20% and 56.89%, respectively, while the resudual out-of-plane modulus and strength were 44.65% and 47.23%, respectively. The results showed that the material exhibited the pesudo-plastical behaviour after oxidation, cracks grew along the punched conical structures formed by the punching technology. In-plane and out-of-plane modulus were more sensitive than their strengths after first oxidation cycle.

The Engine Casing Machining Holes Repairing Based on Vibration Wire Feeding

The engine casing components operate in high-temperature and high-pressure environments. Process holes are drilled when defects occur. Welding is employed in the repair of process holes as a process for permanently joining materials. The traditional welding method relies on padding, which results in poor back formation of process holes. Additionally, the shape of the process holes imposes high requirements on the size of the droplet transition. The conventional approach of adjusting a welding current makes it difficult to achieve stable droplet transition and precise formation of small holes. It poses a challenge for the robotic welding process. To deal with this problem, the influence of the high-frequency vibration GTAW process on the directional transition of molten droplets is studied. The molten droplet directional transition process is developed. The impact of vibration energy on the molten pool is reduced. Welding repair experiments for process holes are successfully conducted. When the frequency is 3 Hz, the transition of droplets changes from a continuous one-droplet transition to a discontinuous liquid bridge transition. The residual height and mechanical properties of the repaired area are tested. The experimental results indicated that the residual height after dual-side repair is ≤0.7 mm. The X-ray and fluorescent penetration tests have a 100% first-pass qualification rate. The repaired area demonstrates a hardness of 480 HV and a room-temperature tensile strength of 1069 MPa. The repair process requirements for the casing are met.

Sorghum and cowpea intercropping response to woody residue amendments in Sahelian agro-ecosystems of Burkina Faso

In West African agro-ecosystems, soils are inherently low in soil organic carbon decreasing the capacity of soils to sustain crop productivity. Woody Residues instead of being burnt or exported out of the cropping systems, can be managed to optimize soil organic carbon build-up, nutrient cycling and crop productivity. The aim of this study was to determine the effect of woody residue amendments from Piliostigma reticulatum (D.C.) Hochst associated with sorghum-cowpea intercropping on the soil residual property and crop productivity. The investigation was carried out in two experimental sites in the Sudano-Sahelian (Gampela and Kulungu) area of Burkina Faso (West Africa). The experimental design was organized into four replicates consisting of two treatments of woody residue amendments: amended (WR+) and unamended (WR-) soils. The results for both sites showed an overall significant increase in numbers (+ 35%) and biomass (+ 64%) of cowpea nodules. The root and aerial biomasses at the flowering stage of cowpeas were significantly improved in amended soils (WR+) by 26% and 44%, respectively compared to unamended soils (WR-). In addition, the WR+ treatment increase significantly cowpea and sorghum yields by 41% and 25%, respectively, as well as water use efficiency (+ 40% and + 26%, respectively) compared to the WR- treatment. Moreover, our results exhibited a strong correlation (r = 0,95) between cowpea nodular biomass and sorghum grain yields, reflecting more contribution of cowpea ecosystem services (facilitation and complementarity) for associated sorghum productivity. However, despite favorable soil conditions (soil water and organic carbon content) that occurred by WR input, it was not sufficient to improve soil residual total nitrogen and available phosphorus. The woody residue management associated with cereal-legume intercropping is a promising option to sustain crop productivity in Sahelian agro-ecosystems.

Influence of Gypsum on the Residual Properties of Fly Ash-Slag-Based Alkali-Activated Concrete

High-temperature exposures of concrete lead to serious damage in concrete structures, resulting in the significant decay of mechanical properties and spalling of concrete. Alkali-activated concretes (AAC) of blended aluminosilicate precursors and activators have been proven to have higher thermal endurance than conventional portland cement concrete. Incorporation of gypsum (GY) in alkali-activated systems has proven to positively impact the mechanical properties when adopted in controlled amounts. GY releases SO42- to the binder system, which helps in the formation of ettringites, along with Ca2+, which leads to the formation of hydrates. This causes a reduction in porosity and improves strength gain. Incorporation of GY into the fly ash-slag-based alkali-activated system further improves thermal endurance by retaining considerable residual strengths even after 800°C exposure. In the present study, the influence of GY on the residual mechanical properties of fly ash-slag-based AAC is investigated to explore the thermal endurance of the ternary mix at elevated temperatures. The mechanical properties of fly ash (FA), Ground Granulated Blast Furnace Slag (GGBS), and gypsum (GY) ternary blended AAC subjected to elevated temperatures are studied in comparison with conventional portland cement concrete (control mix). AAC design mixes with varying proportions of GY as a replacement to FA-GGBS precursor are tested for mechanical properties to obtain the optimum mix. The residual mechanical properties of the FA-GGBS-GY optimum ternary AAC mix are obtained after exposure to elevated temperatures up to 800°C. The morphology and microstructural characteristics of AAC are studied by Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) analyses to investigate the influence of gypsum on the thermal endurance of concrete when exposed to elevated temperatures. Improved thermal endurance is observed for AAC when FA-GGBS precursors are replaced with 5% of GY as compared to the thermal endurance of conventional portland cement concrete (PCC) of the same compressive strength. Doi: 10.28991/CEJ-2024-010-03-017 Full Text: PDF

How to successfully improve the biodiversity of city grasslands?

Urban grasslands (UG) are among the most common types of urban green areas. They are usually species poor, and spontaneous plant migration, which can increase biodiversity, is limited. To improve the range of ecosystem services provided by UG, various seed mixtures are applied during the establishment and restoration of UG. These mixtures vary in content, quality, and cost. High-quality seed mixtures are expensive and are usually only available in small amounts. Meanwhile, alternative methods of seed introduction (e.g., fresh hay application, seeds harvested by brush) have not been well studied in UG restoration, and inexpensive commercial mixtures could have low quality and lead to poor restoration outcomes. Here, we tested the effectiveness of different seed sources to create high-quality UG at two study sites. Based on the results, all seed addition methods increased the species richness of restored grasslands. The outcome of seed addition was satisfactory regardless of differences in residual vegetation species composition and soil properties between the sites. The species richness on plots that received a commercial mixture of flower meadow plants dedicated to pollinators decreased after overwintering. The alternative seed sources (fresh hay and seed incidentally collected during mowing) yielded grassland quality that was comparable to that on plots that received high-quality mixtures with known seed origin (a seminatural meadow mixture and a mixture with the addition of grasses).

The strengthening role of post-welded cryogenic treatment on the performance and microstructure of 304 austenitic stainless steel weldments

The metallurgical changes and micro defects after welding can influence the mechanical property, corrosion resistance and dimensional stability of the stainless steel wielding joints. It is necessary to explore an effective post-welded method to improve the service performance for stainless steel welding joints. Furthermore, the essential mechanism between microstructure changes and macro-property variation during this process needs deep reveal. Therefore, this paper aims at investigating the effects of different post-weld treatments including naturally aging, artificial aging and cryogenic treatment on the residual stress and mechanical properties of 304 stainless steel weldments. The microstructure evolution was also studied to reveal and establish the microstructure-performance relationship. The results showed that the distribution of residual stress was most uniform with lowest magnitude (decreased by up to 49%) after cryogenic treatment. At room temperature, weldments subjected to the three post treatments showed similar mechanical properties. At cryogenic temperature, cryogenic treatment exhibited an outstanding role on maintaining the mechanical properties of weldments. By contrast, the mechanical properties were obviously reduced by artificial aging. The transformation of δ-ferrite and the carbide precipitation in grain boundaries are the main reasons for the decrease of mechanical properties after artificially aging. Welding process was able to cause the transfer of the alloying elements and decrease the stability of austenite. Consequently, martensitic transformation can be induced during cryogenic treatment. The new formed martensite resulted in the refined microstructure and high mechanical properties of weldments, and also the release of residual stress after welding.