Microstructure and mechanical properties of high performance Mg-Gd based alloys

The Mg-12Gd-4Y-2Nd-0.3Zn-0.6Zr (wt.%) alloy was prepared by casting technology, and the structure, age hardening behavior and mechanical properties of the alloy have been investigated. The results demonstrated that the alloy was composed of alpha-Mg matrix, a lot of dispersed Mg24RE5 (RE = Gd/Y/Nd) and Mg5RE precipitates in the as-cast and the T6 state alloys. The alloy exhibited remarkable age hardening response and excellent mechanical properties from room temperature (RT) to 300 degrees C by optimum solid solution and aging conditions. The ultimate tensile strength.

Microstructures, mechanical properties and corrosion behavior of high-pressure die-cast Mg-4Al-0.4Mn-xPr (x=1, 2, 4, 6) alloys

Mg-4Al-0.4Mn-xPr (x = 1, 2, 4 and 6 wt.%) magnesium alloys were prepared successfully by the high-pressure die-casting technique. The microstructures, mechanical properties, corrosion behavior as well as strengthening mechanism were investigated. The die-cast alloys were mainly composed of small equiaxed dendrites and the matrix. The fine rigid skin region was related to the high cooling rate and the aggregation of alloying elements, such as Pr. With the Pr content increasing, the alpha-Mg grain sizes were reduced gradually and the amounts of the Al2Pr phase and All, Pr-3 phase which mainly concentrated along the grain boundaries were increased and the relative volume ratio of above two phases was changed. Considering the performance-price ratio, the Pr content added around 4 wt.% was suitable to obtain the optimal mechanical properties which can keep well until 200 degrees C as well as good corrosion resistance. The outstanding mechanical properties were mainly attributed to the rigid casting surface layer, grain refinement, grain boundary strengthening obtained by an amount of precipitates as well as solid solution strengthening.

Microstructure and mechanical properties of Mg–12.3Zn–5.8Y–1.4Al alloy

Microstructure and mechanical properties of as-cast and heat-treated Mg–12.3Zn–5.8Y–1.4Al (ZYA1261) alloy were investigated. The phase compositions of the as-cast alloy are -Mg, Mg3YZn6 (I-phase), Mg3Y2Zn3 (W-phase), Mg12YZn (Z-phase), Mg24Y5, MgZn and a small quantity of Al-containing phase. The phase compositions change with various heat treatment conditions. The highest Vickers hardness is obtained in the alloy aged at 200 ◦C for 5 h, the transmission electron microscopy indicated that fine scale Z-phase precipitates in the matrix. The tensile properties of the as-cast and heat-treated alloys were reported.

Mechanism of nucleation and precipitation in Li containing Al-Zn-Mg-Cu alloys

Investigations on the aging hardening behavior of four Al-Li-Zn-Mg-Cu alloys were carried out using differential scanning calorimetry, transmission electron microscopy and hardness measurement. It is shown that the addition of Li inhibits the formation of Zn-rich G.P. zones in Al-Zn-Mg-Cu alloys. The dominant aging hardening precipitates is delta'(Al3Li) phase. Coarse T ((AlZn)(49)Mg-32) phase, instead of MgZn2, precipitates primarily on grain boundaries, and provides little strengthening. The multi-stop aging involving plastic deformation introduces in the matrix a high concentration of structural defects. These defects play different role on the nucleation of Zn-rich G.P. zones in different alloys. For the Li free alloy, structural defects act as vacancy sinks and tend to suppress the homogeneous precipitation of G.P. zones, while for the Li containing alloys, these defects promote the heterogeneous nucleation of G.P. zones and metastable MgZn2. A significant aging hardening effect is attained in deformed Li containing alloys due to the extra precipitation of fine MgZn2 in the matrix combined with deformation hardening.

Effects of heat-treatment processes on the electroless Ni-B coating and its natural aging mechanism

A Ni-B coating was prepared with EN using potassium borohydride reducing agent. The as-plated micro-structure of the coating was confirmed from XRD to be a mixture of amorphous and supersaturated solid solution. Three kinds of phase transformation were observed from the DSC curve. Different from the previous works, the formation of Ni4B3 and Ni2B was found during some transformation processes. The key factors which influence the variation of micro-hardness and micro-structure in deposits are the formation, the size and amount of Ni3B, Ni4B3 and Ni2B. Aging of the deposits treated under some heat treatment conditions occurred at room temperature. Changes of the micro-hardness indicated aging phenomena evidently. the natural aging phenomena are concerned with various kinds of decomposition of borides, especially with Ni4B3 phase. The extent of natural aging depends on the formation and the quantity of Ni(4)B3 and Ni2B.

Thermal and mechanical properties of poly(epsilon-caprolactone) crosslinked with gamma radiation in the presence of triallyl isocyanurate

Poly(epsilon-caprolactone) was crosslinked by gamma radiation in the presence of triallyl isocyanurate. The influence of gamma-radiation crosslinking on the thermal and mechanical properties of poly(epsilon-caprolactone)/triallyl isocyanurate was investigated. Differential scanning calorimetry analyses showed differences between the first and second scans. Dynamic mechanical analysis showed an increase in the glass-transition temperature as a result of the radiation crosslinking of poly(epsilon-caprolactone). Thermogravimetric analysis showed that gamma-radiation crosslinking slightly improved the thermal stability of poly(epsilon-caprolactone). The 7 radiation also strongly influenced the mechanical properties. At room temperature, crosslinking by radiation did not have a significant influence on the Young's modulus and yield stress of poly(E-caprolactone). However, the tensile strength at break and the elongation at break generally decreased with an increase in the crosslinking level. When the temperature was increased above the melting point, the tensile strength at break, elongation at break, and Young's modulus of poly(epsilon-caprolactone) were also reduced with an increase in the crosslinking level. The yield stress disappeared as a result of the disappearance of the crystallites.

Precipitates formed in a Mg-7Y-4Gd-0.5Zn-0.4Zr alloy during isothermal ageing at 250 degrees C

The ageing behavior of an extruded Mg-7Y-4Gd-0.5Zn-0.4Zr alloy during ageing at 250 degrees C has been investigated. Two types of phases have been observed during the ageing process. One is a lamellar phase with a 14H long periodic stacking structure, the other is the beta' phase with an ellipsoidal morphology. The increased mechanical properties of the peak-aged alloy are mainly ascribed to the presence of both of these phases at peak hardness.

The mechanical properties of an aluminum alloy by plasma-based ion implantation and solution-aging treatment

The age-strengthening 2024 aluminum alloy was modified by a combination of plasma-based ion implantation (PBII) and solution-aging treatments. The depth profiles of the implanted layer were investigated by X-ray photoelectron spectroscopy (XPS). The structure was studied by glancing angle X-ray diffraction (GXRD). The variation of microhardness with the indenting depth was measured by a nanoindenter. The wear test was carried on with a pin-on-disk wear tester. The results revealed that when the aluminum alloys were implanted with nitrogen at the solution temperature, then quenched in the vacuum chamber followed by an artificial aging treatment for an appropriate time, the amount of AIN precipitates by the combined treatment were more than that of the specimen implanted at ambient temperature. Optimum surface mechanical properties were obtained. The surface hardness was increased and the weight loss in a wear test decreased too.

Investigation on the microstructure and mechanical properties of a cast Mg–6Zn–5Al–4RE alloy

Mg-6Zn-5Al-4RE (RE = Mischmetal, mass%) alloy was prepared by metal mould casting method. The microstructure and mechanical properties of the as-cast and heat-treated alloys were investigated

The microstructure and mechanical properties of Mg-3Al-3RE alloys

The Mg-3Al-3RE alloys (RE, the cerium-rich or the yttrium-rich misch metal) were smelted in a resistance furnace under the protective flux from the Mg-RE master alloys and pure magnesium ingots. The microstructure and mechanical properties of samples prepared by steel mould casting method were investigated.

Aging behavior and mechanical properties of Mg-Gd-Ho alloys

The Mg-8Gd-0.6Zr-xHo (x = 1, 3 and 5, mass%) alloys were prepared by casting technology, and structures, aging strengthening mechanism and mechanical properties of the alloys were investigated. The age behaviors and the mechanical properties are improved by adding Ho addition. The structures of the alloys are characterized by the present of rosette-shaped equiaxed grains. The peak hardness value of the Mg-8Gd-0.6Zr-3Ho alloy is 100 Hv, which is about 30% higher than that of Mg-8Gd-0.6Zr alloy.

Microstructures and mechanical properties of as-cast Mg–5Al–0.4Mn–xNd (x=0, 1, 2 and 4) alloys

Mg-5Al-0.4Mn-xNd (x=0, 1, 2 and 4wt.%) alloys were prepared by metal mould casting method. The microstructures and mechanical properties were investigated. The results demonstrated that Al11Nd3 phase was formed and mainly aggregated along the grain boundaries with the addition of Nd. Meanwhile, the grain sizes were greatly reduced with the increasing Nd content.

The effect of La or Ce on ageing response and mechanical properties of cast Mg-Gd-Zr alloys

Mg-8Gd-0.6Zr-1RE (RE = La or Ce, wt.%) alloys were prepared by casting. The microstructures, age hardening behavior and mechanical properties were investigated. The results show that the addition of 1 wt.% La or Ce to a Mg-8Gd-0.6Zr alloy reduces the dendrite arm spacing and slightly improves the mechanical properties and age hardening response.

Microstructure and mechanical properties of Mg-4.5Zn-xNd (x=0, 1 and 2, wt%) alloys

Microstructure and mechanical properties of Mg-4.5Zn-xNd (x = 0, 1 and 2, wt%) alloys heat-treated at 603 K for 2 It have been investigated. T-phase (an Mg-Zn-Nd ternary phase) was observed in the Nd containing alloys. The optimal mechanical properties were obtained in the Mg-4.5Zn-1Nd alloy, and the ultimate tensile strength and yield strength were 228 and 79 MPa, respectively. Through comparing with the Mg-4.5Zn alloy, the increments of ultimate tensile strength and yield strength were 51 and 17 MPa.