- freely available
Materials 2019, 12(10), 1651; https://doi.org/10.3390/ma12101651
2.2. Preparation of AZ91D/45 Steel
3. Results and Discussion
3.1. Analysis of Hot-Dipping Galvanized Coating
3.2. Analysis of Galvanized-Steel/AZ91D
3.3. Bonding Mechanism of Galvanized-Steel/AZ91D
4. Corrosion and Mechanical Properties
4.1. Corrosion Test
4.2. Microhardness Distribution at the Galvanized-Steel/AZ91D Compound Interface
4.3. Shear Test of 45 Steel/AZ91D
- In galvanized-45 steel/AZ91D bimetallic material, based on the existence of the interface zone, the metallurgical bonding between galvanized-45 steel and AZ91D was achieved via pouring the molten magnesium alloy into the mold inserted into galvanized 45 steel. However, there was only mechanical bonding between bare steel and AZ91D via solid-liquid compound casting.
- The interface zone between galvanized 45 steel and AZ91D could be divided into three different layers. The layer adjacent to the AZ91D (layer I) was mainly composed of a (α-Mg + MgZn) eutectic structure and a black block phase (α-Mg). The layer close to the 45 steel (layer III) was mainly comprised of small white block FeAl3 and black block α-Mg, and the intermediate layer (layer II) consisted of a white uniform lamellae phase (α-Mg + MgZn) eutectic structure.
- The galvanized-45 steel on the surface of galvanized-steel/AZ91D bimetallic material could effectively improve the corrosion resistance of AZ91D, which could be proved by the fact that corrosion potential increased from −1.493 V to −1.143 V and corrosion current density changed from 3.015 × 10−5 A/cm2 to 1.34 × 10−7 A/cm2.
- With the change of the composition in different layers, the microhardness of galvanized-steel/AZ91D bimetallic material varied from location to location. From the layer I to the layer II, the microhardness increased gradually from 104.8 HV to 139.3 HV due to the increasement of MgZn phase contents. But from layer II to layer III, the microhardness changed rapidly from 139.3 HV to 325.4 HV, because the microhardness of the FeAl3 was much larger than the MgZn phases.
- The shear strength of galvanized-steel/AZ91D bimetallic material was much better than bare 45 steel/AZ91D bimetallic material, because of the metallurgical bond replacing the mechanical bond.
Conflicts of Interest
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|Sample||Shear Strength (MPa)||Average Shear Strength (MPa)|
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