The Reliability of Single-Step and Double-Step Quench and Partitioning Heat Treatments on an AISI 420A Low Carbon Martensitic Stainless Steel
Bibliographic record
Abstract
Abstract The microstructural and mechanical effects of various single-step (SS) and double-step (DS) quench and partition (Q&P) heat treatments applied to an AISI 420A low carbon martensitic stainless steel (MSS) has been studied. The goal with this work is to reach a total elongation ( E pct) of 12 pct and an ultimate tensile strength (UTS) above 1200/1300 MPa, but ultimately to achieve a superior strength-ductility balance in comparison to its traditional Quench and Temper (Q&T) counterpart. This is being done by retaining austenite within the steel’s martensitic matrix at room temperature (RT) using novel SS and conventional DS Q&P heat treatments. Considerable work has been done to optimize DS Q&P heat treatments, but little has been done to understand the effects of removing a subsequent heating cycle through SS Q&P heat treatments has on MSSs. With that being said, partitioning is performed at the same quench interruption temperature for the SS Q&P heat treatments, and reheated to a higher temperature for the DS Q&P heat treatments. Experimental investigations were carried out on 1 mm thick, sheet samples to increase the number of potential applications for this steel and heat treatment. The microstructure of different SS and DS Q&P heat treatments was investigated through X-ray diffraction (XRD) and transmission electron microscopy (TEM) while mechanical property investigations were carried out using tensile and fracture toughness testing. DS Q&P heat treated samples quenched to 130 °C and partitioned for industrially relevant times of 10 and 30 minutes featured the highest values in terms of total elongation, tensile strength and fracture toughness. The SS Q&P heat treatments, on the other hand, were able to achieve improved mechanical properties to its Q&T counterpart. Overall, this work opens up the possibility of increased MSS usage for reliable, thin-walled component production with improved properties through Q&P heat treatment methods. The best results achieved in this study are a UTS of 1585 MPa, E pct of 22 pct, and a fracture toughness of 77 kJ/m 2 . Their lower total elongation of 9.6 pct is balanced by high tensile strength of 1812 MPa, ensuring higher toughness compared to traditional Q&T samples.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".