Parent Material Properties Research Articles

Specifics of Experimental and Fem Approaches in Structural Integrity Assesment of Penstock Made of HSLA Steel

Taking into account the history of problems concerning high-strength low-alloyed (HSLA) steel used for manufacturing of penstocks (partly presented by authors in previous studies), this paper is oriented toward specifics on structural integrity assessment of construction in question. Experimental testing of parent material, i.e. HSLA steel, such as microstructure analysis, impact toughness testing and hardness measuring provide insight into characteristics of parent material properties. Considering geometry of penstock and specific requirements, finite element method (FEM), i.e. ABAQUS, was used to assess the structural integrity of penstock as a whole, specific the longitudinal welded joint under the different internal (working) pressure. It should be emphasized that a slight undermatching effect was investigated by FEM approach in this case. Focus is being put on plastic deformation investigation on aforementioned welded joint under maximum internal pressure of 120 bar.

Significant Differences in Microbial Soil Properties, Stoichiometry and Tree Growth Occurred within 15 Years after Afforestation on Different Parent Material.

The mineralogical composition of the parent material, together with plant species and soil microorganisms, constitutes the foundational components of an ecosystem's energy cycle. Afforestation in arid-semi arid regions plays a crucial role in preventing erosion and enhancing soil quality, offering significant economic and ecological benefits. This study evaluated the effects of afforestation and different parent materials on the physicochemical and microbiological properties of soils, including microbial basal respiration (MR), as well as how these changes in soil properties after 15 years influence plant growth. For this purpose, various soil physicochemical parameters, MR, soil microbial biomass carbon (Cmic), stoichiometry (microbial quotient = Cmic/Corg = qMic and metabolic quotient = MR/Cmic = qCO2), and tree growth metrics such as height and diameter were measured. The results indicated that when the physicochemical and microbiological properties of soils from different bedrock types, along with the average values of tree growth parameters, were analyzed, afforestation areas with limestone bedrock performed better than those with andesite bedrock. Notably, sensitive microbial properties, such as Cmic, MR, and qMic, were positively influenced by afforestation. The highest values of Cmic (323 μg C g-1) and MR (1.3 CO2-C g-1 h-1) were recorded in soils derived from limestone. In contrast, the highest qCO2 was observed in the control plots of soils with andesite parent material (7.14). Considering all the measured soil properties, the samples can be ranked in the following order: limestone sample (LS) > andesite sample (AS) > limestone control (LC) > andesite control (AC). Similarly, considering measured plant growth parameters were ranked as LS > AS. As a result, the higher plant growth capacity and carbon retention of limestone soil indicate that it has high microbial biomass and microbial activity. This study emphasizes the importance of selecting suitable parent material and understanding soil properties to optimize future afforestation efforts on bare lands.

Investigations on the influence of hot rolling on the creep characteristics of additively manufactured Mg-5Ag alloy

The requirement for lightweight materials that can survive increasingly severe conditions for aerospace components has fueled the research on magnesium alloys. The current work investigates the influence of hot rolling on the creep characteristics of the Mg-5Ag alloy that is fabricated through a selective laser melting process. The creep properties of parent material (PM) and hot-rolled specimens (HRA) are determined by indentation creep tests at 250 °C, 275 °C, and 300 °C. The microstructural evolution, phase transformation kinetics, and texture evolution were deduced using instrumental analysis, including SEM, EBSD, TEM, and XRD. The specimen PM features α-Mg grains with intermetallic Mg-Ag particles along grain boundaries and random grain orientations with low-angle boundaries. However, specimen HRA has a more fraction of Mg-Ag precipitates, a dominant (0001) grain orientation, and higher peak intensity from the (002) plane. The HRA specimen also demonstrates higher apparent activation energies, attributed to microstructural changes from hot rolling. The results show that the creep resistance of the hot rolled Mg-5Ag alloy is superior to as-fabricated Mg-5Ag alloy based on the creep velocity, stress exponent, and apparent activation energy.

The extended scaling laws of the mechanical properties of additively manufactured body-centered cubic lattice structures under large compressive strains

Additively manufactured lattice structures are porous light-weight structures with mechanical properties that are dictated both from the topology and the parent material properties. When printed from metals, these structures can withstand large continuous plastic deformation. In this paper, we focus on body-centered cubic (BCC) lattice structures under compression up to large deformation strains, and we propose relations between the slenderness ratio of struts and the following mechanical properties: Young's modulus, yield strength, hardening rate of the structure and the densification strain. We perform a systematic study using finite element modelling (FEM) to find how both material properties and lattice structures are affecting the effective mechanical properties of BCC lattice structures under compression. Based on this analysis we propose the scaling laws of the mechanical properties. The scaling laws can be explained as an extension of the Gibson-Ashby power law relations for bend-dominated structures with non-slender beams. We also discuss how rounding the connections between the struts using fillets affects the scaling laws. We demonstrate the scaling laws in the analysis of experimental results, showing the accuracy and limitations of the scaling laws in predicting the mechanical properties, with an emphasis on large deformations. In the analysis, we use experimental values published in literature, and we also present here experimental results of lattice structures printed from Inconel 718.

Spatial variability of clay minerals in a semi-arid region of Turkiye

Clay minerals are the source of many chemical and physical properties that influence the provision of soil-based ecosystem services. This study aimed to identify the most significant soil characteristics contributing to the spatial variability of clay minerals in a semi-arid region of Turkiye. Additionally, the study assessed the predictive capabilities of Classification and Regression Tree (CART), Random Forest Regression (RF) and eXtreme Gradient Boosting Regression (XGBoost) in estimating soil clay mineral content. Smectite+vermiculite (SMVR) was the most abundant clay mineral in the study area, followed by illite and kaolinite. Hyperparameter tuning significantly improved model accuracy, with root mean square error (RMSE) reductions ranging from 2.53% to 97.3%. The machine learning algorithms demonstrated varying performances in spatial prediction accuracy. The RF model achieved the lowest RMSE (8.587%) and the highest R2 values (0.796) for predicting SMVR. The XGBoost outperformed other models for kaolinite (RMSE: 4.814%, R2:0.713) and illite (RMSE:7.368%, R2:0.613). Exchangeable cations, particularly magnesium (Mg) and calcium (Ca), were identified as crucial factors influencing the spatial distribution of clay minerals. Among these, M concentration had the strongest influence on predicting both SMVR (38.1%) and illite (26.3%). Conversely, for kaolinite prediction, Ca concentration played the most significant role (38.7%), followed by Mg (19.93%). In conclusion, this study demonstrates the effectiveness of machine learning models, particularly XGBoost which achieved the lowest RMSE for all clay minerals investigated. These models offer a valuable tool for predicting clay mineral content in the Kazova Plain. The findings highlight the importance of parent material, weathering processes, and specific soil properties, such as exchangeable cations, in shaping clay mineral distribution. This knowledge not only contributes to a deeper understanding of soil formation in semi-arid environments but also practical applications. For instance, by predicting the abundance of SVMR, known for its high cation exchange capacity land managers can develop targeted strategies for optimizing fertilizer application in the Kazova Plain.

Mechanical properties of corner material in cold-formed steel structure: From normal strength to high strength

Cold-forming effect varies from normal strength steel to high strength steel due to the different chemical compositions and mechanical properties of parent materials. To date, research studies on material characterisation of cold–formed steels have been mainly focusing on the normal strength structural steel, while systematic research on high strength structural steel remains scarce. In this paper, an experimental investigation into changes in mechanical properties of high strength steel undergoing various levels of plastic deformation is firstly presented. The test results have been combined with other available high strength steel data, and compared to the normal strength steel data. Of the analysis results indicated, unified predictive equations, modified from Karren’s model in 1967 can predict the strength enhancement behaviours of normal strength and high strength steel, utilising the ultimate-to-yield strength ratio of parent materials fu,f/fy,f and inner radius-to-thickness ratio after cold–forming ri/t. Moreover, the decreases in the Young’s modulus, ultimate strain and elongation at fracture of normal strength and high strength steel after cold-forming can be predicted with no further grouping required. Statistical evaluation results confirm the accuracy of the proposed predictive expressions. This paper extends the scope of the strength enhancement equation in current north American cold-formed steel design code AISI S100–16 to high strength steels with grade up to 960 MPa, and provides key predictive material equations that can be further used in the design or numerical modelling of cold-formed steel structures.

Investigation on cost-effective composites for CO2 adsorption from post-gasification residue and metal organic framework

Cost-effective CO2 adsorbents are gaining increasing attention as viable solutions for mitigating climate change. In this study, composites were synthesized by electrochemically combining the post-gasification residue of Macadamia nut shell with copper benzene-1,3,5-tricarboxylate (CuBTC). Among the different composites synthesized, the ratio of 1:1 between biochar and CuBTC (B 1:1) demonstrated the highest CO2 adsorption capacity. Under controlled laboratory conditions (0°C, 1 bar, without the influence of ambient moisture or CO2 diffusion limitations), B 1:1 achieved a CO2 adsorption capacity of 9.8 mmol/g, while under industrial-like conditions (25°C, 1 bar, taking into account the impact of ambient moisture and CO2 diffusion limitations within a bed of adsorbent), it reached 6.2 mmol/g. These values surpassed those reported for various advanced CO2 adsorbents investigated in previous studies. The superior performance of the B 1:1 composite can be attributed to the optimization of the number of active sites, porosity, and the preservation of the full physical and chemical surface properties of both parent materials. Furthermore, the composite exhibited a notable CO2/N2 selectivity and improved stability under moisture conditions. These favorable characteristics make B 1:1 a promising candidate for industrial applications.

Diffuse Reflectance Spectroscopy for Mapping Soil Carbon Stock in the Gilbués Desertification Region at Brazilian Cerrado

The carbon stock (C Stock) is a key soil attribute, especially in areas under degradation. The objective of this study was to map the C Stock and other physical and chemical attributes on the soil surface of a micro-watershed located in the Gilbués Desertification Nucleus and to calibrate pedometric functions to map them, applying spectra obtained by Diffuse Reflectance Spectroscopy (DRS) in the near-infrared (NIR) region. This study was developed in the Piripiri Stream Micro-watershed (PSMW), which presents different levels of degradation. A total of 214 composite soil samples were collected from the 0–0.10 m depth layer. Spectral and laboratory analyses were performed following traditional methods. The results from 100 samples were subjected to descriptive analysis, pedometric modeling, and geostatistics, while the remainder were used exclusively for the prediction and modeling of the predicted attribute maps. C Stock ranged from 0.3 to 11%, with the highest values associated with the least sandy sites. We assert that stakeholders, including government agencies, could utilize DRS for mapping main soil attributes, such as C Stocks, soil granulometry, or total organic carbon, in regions characterized by similar parent material and soil properties. This application can support informed decision-making regarding land management in extensive areas facing soil threats.

Fluorescent Co/Al-layered double hydroxide intercalated Schiff base-chitosan composite for sensing multiple e-waste metals

An organic-inorganic composite was fabricated by the intercalation of chitosan Schiff base (Chitosan@SB) in the layers of Co/Al layered double hydroxide (Co/Al-LDH) to get the amalgamated properties of parent materials like fluorescent nature and porosity. The structural properties of Chitosan Schiff base intercalated layered double hydroxide (Chitosan@SB-Co/Al-LDH) were explored through FT-IR, PXRD, TGA, BET, HRTEM, and SEM analysis. The composite Chitosan@SB-Co/Al-LDH showed a fluorescence peak pointed at 501 nm (λexc = 370 nm) and a porous surface with heterogeneous texture. It showed an outstanding turn-off signal in the presence of selective metallic species i.e., Cu2+, Fe3+, Al3+, Cr3+, Hg2+, and Pb2+ ions thus acting as a sensing probe for the e-waste metals. Moreover, the Density-Functional Theory supports the procedure of interaction between Chitosan@SB-Co/Al-LDH and metal ions. Furthermore, the composite has been investigated for real life uses in sewage waste water samples.

Grain size and shape dependent crystal plasticity finite element model and its application to electron beam welded SS316L

Electron beam welding is an autogenous welding process that leads to microstructural heterogeneities; crystallographic texture, elongated and larger grain size relative to the surrounding parent material. The goal of this study is to predict the changes in mechanical response of the weld fusion zone as a function of grain morphology and texture by using the parent material properties to avoid extensive and costly experimental campaigns. For this reason, a crystal plasticity solver, “University of BRIstol cryStal plasTicity sOLver” (BRISTOL), is implemented in a finite element framework with new constitutive laws to account for the length-scale dependence considering the size and shape of the grains. It is found that the crystallographic texture governs the orientation specific elastic stiffness and yield stress having the most dominant effect on the macroscopic response of the weldment at the grain size scales considered. Crucially the length-scale dependent model allows accurate prediction of the yield strength of the weldment over a range of microstructures, also highlighting the presence of other factors such as prior strain hardening during the welding process and residual stresses.

Unexpected catalytic activity of nanorippled graphene

Graphite is one of the most chemically inert materials. Its elementary constituent, monolayer graphene, is generally expected to inherit most of the parent material's properties including chemical inertness. Here, we show that, unlike graphite, defect-free monolayer graphene exhibits a strong activity with respect to splitting molecular hydrogen, which is comparable to that of metallic and other known catalysts for this reaction. We attribute the unexpected catalytic activity to surface corrugations (nanoscale ripples), a conclusion supported by theory. Nanoripples are likely to play a role in other chemical reactions involving graphene and, because nanorippling is inherent to atomically thin crystals, can be important for two-dimensional (2D) materials in general.

Method for evaluating the ductile fracture properties of steel parent material and weld metal

Method for evaluating the ductile fracture properties of steel parent material and weld metal

Geochemical characteristics of soil selenium and evaluation of selenium-rich land resources in Guiyang area

Selenium concentration in soil is of great importance for the production of selenium-rich crops. In this article, we studied the geochemical characteristics of soil selenium and evaluated selenium-rich land resources in the Guiyang city area using results from a Guizhou multi-purpose regional geochemical survey. The results indicate that 1) the selenium content in topsoil in the Guiyang area ranges from 0.11 to 4.12 mg kg−1, with an average value of 0.70 mg kg−1, which is 2.4 times and 3.5 times the national and world soil background values, respectively, while the selenium content in deep soil ranges from 0.11 to 4.10 mg kg−1, with an average value of 0.42 mg kg−1, which is 1.4 and 2.1 times the national and world soil background values, respectively; in the vertical profile, the selenium content in soil decreases with the increase in soil depth. 2) The main factors affecting the distribution of selenium in soil include soil parent material, soil physical and chemical properties, and other components, such as soil type and land use, among which the soil parent material (rock) plays a decisive role. The selenium in soil mainly comes from the soil parent rock, increasing accordingly with the increase of the selenium background value of the parent rock; the physical and chemical properties of the soil and other components impose certain influences on the selenium content. Selenium presents a significant linear positive correlation with sulfur and organic carbon, while it has a negative correlation with the pH value; there is no significant difference in the selenium content in different soil types, following the distribution order of paddy soil >yellow soil> skeletal soil> lime soil> purple soil; land use has a certain effect on selenium in soil, following the distribution order of garden land > construction land > grassland > farmland > rocky hills > forest land. 3) The area of selenium-enriched soil in the study region is 11,408 km2, with 91.76% of selenium-enriched soil and 8.24% of general soil or extremely little excess-selenium soil. Therefore, the vast majority of soil in Guiyang is selenium-enriched. The city has large and abundant selenium-enriched areas, which are domestically and internationally rare and provides particularly favorable resource conditions for developing selenium-enriched efficient mountain agriculture to expedite rural revitalization.

Održavanja železničkih komponenti primenom procesa eletrolučnog navarivanja

The service performance and life of rail components are subjected to the following wear mechanisms: metal to metal or adhesive wear; fatigue; plastic flow and defects in rail and welds. Standard and head hardened rail grades made of high carbon steel as well as crossing made of austenitic manganese steels require permanent in field as well as workshop maintenance. Arc welding has been widely used for the repair and maintenance of rail components. This paper focuses on repairs of railway components using flux cored arc welding as a process with higher productivity, reliability, quality and increased service life of the repaired components. The paper addresses metallurgical aspects of the rail components welding, development of welding procedures, welding filler materials selection, heat input and temperature control, dilution and distortion control, weld, heat affected zone and parent material properties.

Synthesis of {P2W18}-based coated structured nano materials with supercapacitors and H2O2 sensing

The combination of metal-organic frameworks (MOFs) with large specific surface area and high stability and Dawson-type polyoxometalates (POMs) with excellent electron transfer ability to build a new inorganic-organic hybrid as energy storage materials can give full play to the advantages of both. Therefore, the inorganic organic hybrid nano material {Ag4K2P2W18O62}@[Ag3(μ-Hbtc)(μ-H2btc)]n (which became {Ag4K2P2W18O62}@Ag-BTC, where BTC = 1,3,5-benzenetricarboxylic acid) was synthesized by liquid-assisted grinding. The XRD, SEM, TEM characterization show that {Ag4K2P2W18O62}@Ag-BTC is a coating structure. The specific capacitance is 378.9 F g−1 at a current density of 1 A g−1, with a retention rate of 93.5 % for 5000 cycles. An energy density of 7.8 Wh kg−1 and the power density of 500.0 W kg−1 are obtained in water-based symmetric two-electrode supercapacitor system. In addition, when used as an H2O2 sensor, it has a broad detection range of 1.5 μM to 1.5 mM and the small detection limit of 0.206 μM, also offers excellent interference immunity and stability. Moreover, by applying this nano material to the detection of H2O2 in human serum, results are acceptable. The above result shows that the composite material synthesized by the liquid-assisted grinding method adequately combines properties of both parent materials is a viable strategy for achieving performance enhancement.

Creep properties of ASTM A335 P92 pipe parent material and erection welded joint simulation: effect of 1 or 3 PWHT

ABSTRACT Field experience with new generation CSEF steels, such as grade 92, is still quite limited. The Italian Creep Group (GdL) launched a testing effort, to characterise creep performance of a pipe weld joint, representative of true current manufacturing and on-site assembly conditions. A P92 pipe from standard production was supplied by Tenaris and welded by AnsaldoEnergia according to standard procedures. Istituto Italiano della Saldatura qualified the welding procedure. Parent material and cross-weld (after one PWHT) creep and tensile behaviour was investigated according to ECCC requirements. Results were presented at ECCC2017 conference.

Variations in fungal community structure along elevation gradients in contrasting Austrian Alpine ecosystems

Soil fungi, as a major decomposer of organic matter, govern carbon (C) cycle and act as crucial regulators of the soil C and nutrient balance in terrestrial ecosystems. Climate change and parent material alter important environmental conditions that may affect fungal community. However, very little is known about the diversity and community structure of soil fungi along elevation gradients with distinct parent material properties. We investigated the effects of climate and vegetation changes on soil fungal diversity and community structure at two Austrian alpine sites with different bedrock properties (limestone at the Hochschwab site and silicate at the Rauris site), but with similar climatic conditions. At these sites we sampled soils from 0 to 25 cm depth along three elevation gradients ranging from 900 to 2100 m above sea level and examined how the fungal communities vary by using Illumina MiSeq sequencing. Our results show that the fungal community structures at the Hochschwab and the Rauris site were defined by elevation-induced changes in vegetation and associated differences in soil pH. In forest soils, symbiotrophic fungi (mainly belonging to the class Agaricomycetes, phylum Basidiomycota) were dominant at the Hoschwab site, while at the Rauris site the Ascomycota were the most dominant phyla. The change to grass dominated vegetation generally increased the contribution of saprotrophic fungi (mainly belonging to various classes of the phylum Mucoromycota) at both elevational sites. Prevalence of ectomycorrhizal fungi and associated lignolytic enzymes induced soil C loss might explain lower soil organic C stocks at the Rauris site compared to the Hochschwab site. Our results suggest that parent material can modulate fungal communities indirectly via vegetation (e.g., litter quality) adapted to particular soil conditions. Therefore, changes in fungal structural composition might exert important consequences on ecosystem C balances.

Measuring landscape evolution from inception to maturity: Insights from a coastal dune system

The concept of the geomorphic cycle is a foundational principle in geology and geomorphology, but the topographic evolution of a single landscape from inception to maturity has been difficult to demonstrate in nature. The onlapping dunes of the Cooloola Sand Mass (CSM) in eastern Australia provide an ideal chronosequence to evaluate landscape evolution. Here commonly assumed properties on which landscape models are based (i.e., conservation of mass and major factors contributing to landscape change) can be physically measured and accounted for. Our field based measurements and forward numerical models demonstrate that dunes, like other landscapes, relax in an exponential manner. The emplaced dunes evolve through an initial phase of rapid topographic adjustment associated with the dominance of landsliding. This phase continues for ∼1 kyr until hillslope gradients are lowered below their angle of repose (0.65 m m−1 or 33°). Once sufficiently lowered, the dunes evolve through slow, soil creep processes. These findings of dual transport regimes are validated by stratigraphic records at all excavated dune foot-slopes and we propose that this evolution can be measured by the distribution of curvature (C) of a landform, specifically its standard deviation (σC), as a measure of surface roughness. Surface roughness smooths with time through diffusional sediment transport that lowers local relief. The value and its rate of smoothing can define the stage in evolutionary development and help infer processes, which makes it an important morphometric tool for understanding landscapes. These observations highlight that under stable evolutionary conditions, the development of the landscape is governed by the physical properties of the dune's parent material. In addition, our findings support landscape evolution inferences from numerical and physical models and the coupling of granular material physics with landscape change.

Microstructure characterization and mechanical properties of 2.25Cr-1Mo steel pipes using pulsed current GTAW

The 2.25Cr-1Mo pipe was designed to withstand high pressures and temperatures in a variety of industries, including steam boiler pipes,offshore oil drilling, power generation, and petrochemicals. 2.25Cr-1Mo is a good choice for fusion welding and forming. Pulsed current GTAW providesthe advantage of joining thin sections with low heat input, leading to less deformation and warpage than TIG welding. It also allows for better weld pool management, enhanced weld penetration, and improved weld quality with less distortion and warpage. It also allows for better weld pool control, enhanced weld penetration, and improved weld quality. The goal of this research is to use a design of experiments technique to optimize process parameters and describe the microstructure and mechanical properties of 2.25Cr-1Mo pipes welded with pulsed current GTAW (DOE). The Taguchi method is used to choose the L9 (34) orthogonal array (OA) for four factors (pulse current (PC), background current (BC), pulse frequency (PF), and pulse on time (PO)) at three different levels on 2.25Cr-1Mo steel pipe joints. The pulsed current GTAW method is used to obtain the optimal combination for increased weld strength. To find the best process parameters for 2.25Cr-1Mo steel pipes, researchers used an analysis of variance (ANOVA). 220 A Pulse current, 120 A background current, 8 Hz pulse frequency, and 60 %pulse on are shown to be the best parameters for 2.25Cr-1Mo steel. Microhardness, Tensile, and Impact tests are done and compared to the parent material's properties. Some bainitic packets at the weld zone have finer lath structures, whereas others have coarser lath structures. The fracture morphology shows tear ridge, cleavage facets, and ductile dimples where failure occurs at the weld zone and it indicates ductility failure.

The role of geochemistry in organic carbon stabilization against microbial decomposition in tropical rainforest soils

Abstract. Stabilization of soil organic carbon (SOC) against microbial decomposition depends on several soil properties, including the soil weathering stage and the mineralogy of parent material. As such, tropical SOC stabilization mechanisms likely differ from those in temperate soils due to contrasting soil development. To better understand these mechanisms, we investigated SOC dynamics at three soil depths under pristine tropical African mountain forest along a geochemical gradient from mafic to felsic and a topographic gradient covering plateau, slope and valley positions. To do so, we conducted a series of soil C fractionation experiments in combination with an analysis of the geochemical composition of soil and a sequential extraction of pedogenic oxides. Relationships between our target and predicting variables were investigated using a combination of regression analyses and dimension reduction. Here, we show that reactive secondary mineral phases drive SOC properties and stabilization mechanisms together with, and sometimes more strongly than, other mechanisms such as aggregation or C stabilization by clay content. Key mineral stabilization mechanisms for SOC were strongly related to soil geochemistry, differing across the study regions. These findings were independent of topography in the absence of detectable erosion processes. Instead, fluvial dynamics and changes in soil moisture conditions had a secondary control on SOC dynamics in valley positions, leading to higher SOC stocks there than at the non-valley positions. At several sites, we also detected fossil organic carbon (FOC), which is characterized by high C/N ratios and depletion of N. FOC constitutes up to 52.0 ± 13.2 % of total SOC stock in the C-depleted subsoil. Interestingly, total SOC stocks for these soils did not exceed those of sites without FOC. Additionally, FOC decreased strongly towards more shallow soil depths, indicating decomposability of FOC by microbial communities under more fertile conditions. Regression models, considering depth intervals of 0–10, 30–40 and 60–70 cm, showed that variables affiliated with soil weathering, parent material geochemistry and soil fertility, together with soil depth, explained up to 75 % of the variability of SOC stocks and Δ14C. Furthermore, the same variables explain 44 % of the variability in the relative abundance of C associated with microaggregates vs. free-silt- and-clay-associated C fractions. However, geochemical variables gained or retained importance for explaining SOC target variables when controlling for soil depth. We conclude that despite long-lasting weathering, geochemical properties of soil parent material leave a footprint in tropical soils that affects SOC stocks and mineral-related C stabilization mechanisms. While identified stabilization mechanisms and controls are similar to less weathered soils in other climate zones, their relative importance is markedly different in the tropical soils investigated.