| Effect of Q&P Heat Treatment on Fine Microstructure and Mechanical Properties of a Low-alloy Medium-carbon Steel |
| Paper ID : 1438-UFGNSM-FULL |
| Authors: |
|
Rahim Jafari *1, Shahram Kheirandish2, Shamseddin Mirdamadi2 1No121, Kowsar Yekom st., Satarkhan Ave. 2Iran University of Science and Technology |
| Abstract: |
| The current research investigates the effect of ultrafine microstructure resulted from Quench and Partitioning (Q&P) process on obtaining ultra-high strengths in a low-alloy steel with 4wt.% carbon. The purpose of Q&P heat treatment is to enrich the austenite with carbon by partitioning of carbon from supersaturated martensite to austenite, in order to stabilize it to the room temperature. The microstructure, consequently, is consists of martensite, retained austenite and in some conditions bainite. Two-step Q&P heat treatment with quench and partitioning temperatures equal to 120°C and 300°C respectively were applied to the samples at different times. Mechanical behavior was studied by tensile test. The microstructure of the samples was observed using SEM, and TEM and to quantify the amount of retained austenite X-ray diffraction was used. The retained austenite grain size was estimated to be about 0.5μm and the highest amount of retained austenite obtained was 10 vol%. All samples showed a yield strength and a tensile strength of above 900MPa and 1500MP respectively. The yield strength increased with increase in partitioning time, whereas tensile strength showed an inverse behavior. The elongation in samples varied from 5% to 9% which seemed to not have a direct connection with the amount of retained austenite, but instead it was related to the ferritic structures formed during partitioning such as coalesced martensite, bainite and tempered martensite. |
| Keywords: |
| Q&P process, retained austenite, fine grained steel, mechanical properties |
| Status : Paper Accepted (Oral Presentation) |
