Papers by Author: Peng Huai Fu

Abstract: The corrosion behavior of GW63 (Mg-6wt.%Gd-3wt.%Y-0.4wt.%Zr) alloys in 5% NaCl aqueous solution has been investigated by PARSTAT 2273 instrument. The Open Circuit Potential (ECORR) vs. time curve, cyclic polarization (Pitting Scans) curve and Electrochemical Impedance Spectroscopy (EIS) was measured for the GW63 alloys in as-cast and T6 heat treatment conditions. The EIS results indicated that the tendency of impedance variation for as-cast condition was monotonic decreasing, however, the tendency of variation for T6 condition was not completely monotonic but the total tendency was decreasing. The values of impedance of GW63 alloy at 0.1 Hz are about 103 ohm-cm2 for as-cast and T6 condition.

Abstract: The microstructure and mechanical properties of Mg-3wt％Nd-0.2wt％Zn-0.4wt％Zr alloy in as-cast, solution-treated and solution-treated + peak-aged were investigated. The alloy had a cast structure with large intergranular Mg12Nd phase between the α-Mg matrix. After solution-treated, the intergranular Mg12Nd phase disappeared and lots of small Zr-containing particles distributed inside the grains. Small plate-like phases precipitated inside the grains strengthened the alloy to a high level after peak-aged at 200°C for 16 hours: the ultimate strength of the alloy up to 305 MPa, with considerable elongation rate 11%, and yield strength 140 MPa. The peak-aged samples also had good creep resistance, with strain rate less than 0.2% after 120 hours creep test under the condition of 110 MPa at 200°C. The minimum creep rate was about 4.64×10-9. The alloy had different fracture pattern in different states: as-cast state, intergranular fracture was the key pattern to failure; after solution-treated, the fracture pattern turned to cleavage transgranular fracture; after peak-aged, the alloy had a mixed fracture pattern of transgranular and intergranular, in which transgranular was the main style.

Abstract: Compact AM50 alloy components were cast by Low Pressure Die Casting (LPDC) process. The microstructure and mechanical properties of cast components were investigated under as-cast and heat treated states. It was found that the microstructure of LPDC AM50 is composed of α-Mg and second phases - Mg17Al12 and Al8Mn5. Compared with Gravity die casting, LPDC AM50 alloy had much coarser grains and higher density, with smaller sizes and less content of second phases. The density of AM50 alloy by LPDC process was ρ=1.7836g/cm3, with increase of 0.45% based on Gravity die casting and much more increase compared with high pressure die casting. The as-cast mechanical properties by LPDC process were: σ0.2=57.8Mpa, σb=192.3Mpa, δ=8.7%. These of Gravity die casting were: σ0.2=53Mpa, σb=173.4Mpa, δ=8.1%. UTS in LPDC increased about 20MPa, with better YTS and Elongation. Compared with that of high pressure die cast AM50, the YTS of LPDC was much lower, with comparable UTS and Elongation. The mechanical properties of the heat treated AM50 alloy were still in the same level of as-cast state. AM50 alloy by LPDC process is not necessary subjected to tempering treatment.

Abstract: The microstructure of Mg-3wt%Nd-0.2wt%Zn-0.4wt%Zr (NZ30K) alloy after solution treatment was investigated and several kinds of interesting phases containing zirconium were found in this study. NZ30K was gravity cast using permanent die casting. After high tempering solution treatment at 540°C, cluster particles were observed inside the grains under optical microscopy. The detailed investigations were carried out on transmission electron microscopy (TEM). Four kinds of precipitates were visible inside grains with different shapes: block-like, globular, short rod-like, long rod-like. The block-like particle was identified as ZrH2 phase and the globular one was Zn2Zr3 phase. The other two were still Zr-containing phases, which could not be identified to any of existed compounds containing Zr. The formation of Zn-Zr compounds would probably be due to relative high ratio of Zr to Zn in the center of grains. ZrH2 would be the results of reaction of zirconium with H element during solution treatment, which probably came into the alloy during melting.