The Microstructure of Fe-Based Laminated Metal Composite Produced by Powder Metallurgy

Powder metallurgy (PM) is a versatile process to manufacture nearly net-shaped metallic materials in industry. In this study, the PM process was used to fabricate two Fe-based laminated metal composites (LMCs), Fe-4Ni-3Cr-0.5Mo-0.5C/Fe and 410/304L. The results showed that after sintering, the LMCs were free of interfacial cracks and distortion, indicating that the PM process is a feasible means for producing these LMCs. In the Fe-4Ni-3Cr-0.5Mo-0.5C/Fe LMC, the diffusion of C resulted in the generation of a continuous pearlite layer between the Fe-4Ni-3Cr-0.5Mo-0.5C and Fe layers and a ferrite/pearlite mixture in the Fe layer. In the 410/304L LMC, the difference in the chemical potentials of C between the 304L and 410 layers led to the uphill diffusion of C from the 410 layer to the 304L layer. A continuous ferrite layer was thus formed near the interface of the 410 layer. Furthermore, a martensite layer of about 50 μm thickness was generated at the interface due to the high Cr and Ni content.

Characterization of Crater Area in a Target Penetrated by a Wf/Zr-Based Amorphous Matrix Composite Projectile

Tungsten fiber-reinforced Zr41.25Ti13.75Cu12.5Ni10Be22.5 amorphous matrix composites (hereinafter referred to as Wf/Zr-based amorphous matrix composites) are considered as a potential new generation of projectile material, while the penetration behavior of Wf/Zr-based amorphous matrix composites is not fully clear yet. In order to better understand the penetration behavior of this composite material and study its armor-piercing performance, a ballistic experiment was performed and the hardness and microstructure around the crater of a target material were studied. A ballistic experiment was performed with a projectile of Wf/Zr-based amorphous matrix composite and a target of 4043 steel. After the ballistic experiment, the target was cut through the crater using a wire cutting machine into a sample with size 150 mm × 40 mm × 20 mm, which was later polished by different types of sandpaper. The micro-hardness was analyzed in a micro-hardness tester, and the microstructure was observed by SEM. According to this study, three layers were identified in the direction lateral to the crater, consisting of a martensite layer, a deformation strengthening layer, and the original structure layer. Moreover, the martensite layer initially thickened and then thinned in the direction longitudinal to the crater.

Microstructure and Fracture Behavior of Special Multilayered Steel

In this research, multilayered steel (MLS), which is composed of middle-carbon martensite steel, high-carbon martensite steel, and a pure Ni thin layer was obtained by the accumulative roll-bonding method. The microstructure and mechanical properties of the MLS were investigated by scanning electron microscopy (SEM), Vickers microhardness, tensile, and bending tests. In-situ SEM tensile tests were used to observe the crack initiation and propagation processes during the tensile loading. The results show that the ultimate tensile strength and bending strength of the MLS can reach 946 MPa and 3153 MPa, and the maximum elongation can reach 18%, which is related to the better combined quality of the interface. The middle and larger martensite layer (ML) becomes the weakest link of tensile fracture and interfacial delamination of the MLS during the tensile processes, because there are lots of large hard blocks Cr23C6 phases distributed in the middle thicker ML layer. Besides, the MLS can withstand larger bending deformation. When the MLS was bent to 180 degrees, neither macro-cracks in the outer side of the bending parts nor interfacial delamination can be found.

Comparative Study on the External Grind-Hardening Experiments of 40Cr Steel and 45 Steel

A new manufacturing technology, external grind-hardening, is put forward and orthogonal tests are carried out with 3-level 3-factor aimming at 40Cr steel and 45 steel. A certain depth of Martensite layer is found on the hardened surfaces of both materials by metallographic observation and the hardness values meet the design requirement, which demonstrates the practicability of the new technology. Orthogonal analysis is proceeded successively for the acquirements of influencing pattern and significance of factors, and comparative study is carried on the hardening effect and feature for the both materials.

Change Regulation of Hardness of Target around Crater Penetrated by Wf/Zr-Based Amorphous Matrix Composite Projectile

Because of excellent mechanical, physical and chemical property Wf/Zr-based amorphous matrix composite attracts people’s interest and becomes the hot spot of science study and engineering application. In this paper, change regulation of hardness of target around crater by Wf/Zr-based amorphous matrix composite projectile and its mechanism are studied after firing test, and it is found that the section can be divided into 3 layers: the Martensite layer, the deformed fine grain layer and the normal matrix from the crater surface to the interior of the steel target and that the thickness of Martensite layer increases first and then decreases in the penetration direction when the velocity of projectile is 1200m/s.

Machined Workpiece Edge Shape Control by Laser Hardening —Optimizing Laser Scan Conditions and Cutter Paths—

Burring is a vital factor in metal cutting processes, since it may cause production-line problems that add unwanted time and cost required for deburring. We found that laser hardening of workpieces before face milling efficiently prevents burr formation. Our purpose here is to study optimum laser hardening conditions and cutter paths. Where no burring occurs, minimal chipping such as in chamfering is seen at the martensite layer on the workpiece exit face. The martensite layer thickens with laser power density, increasing chamfer height. The larger the exit angle, the more difficult it is to form a chamfer-like edge. Even for relatively small exit angles, the lower the feed rate, the more difficult it becomes to form a chamfer-like edge.