Influences of Mg Addition on the Mechanical Properties of Cu-Al-Ni Shape Memory Alloys

Shape Memory Alloys (SMAs) are a unique class of material that possesses unconventional properties such as the shape's memory effect, the high flexibility associated with damping capabilities, high wear resistance and fatigue. Given its use in a variety of technological applications, its studies have attracted increased interest in the community of scientists and researchers during the past decades. The shape memory alloy (Cu 83%-Al 13%-Ni 4%) and the other alloy with adding the alloying elements (Mg) with content of (0.25, 0.5, 0.75, 1.0, 1.25) % as a volumetric ratio which was taken from the copper percentage were prepared by powder metallurgy, The powders were mixed using (V-type) powders mixer with mixing speed and time (20 rpm), (16 min) respectively then the samples were pressed by a two-way press (floating die) and pressing pressure (500 MPa) then the green samples where sintered by using vacuum furnace with using Argon gas medium at a temperature (900°C) for one hour and left in the oven to cool down to room temperature. The results showed that both bulk density and apparent density compared to the base alloy increase by increasing the volumetric fraction of Mg by the ratios (5.49)% compared to the bulk density of the base alloy and by the ratios (1.51)% compared to the apparent density of the base alloy. accompanied by a decrease in the real and apparent porosity and water absorption, The results of the mechanical tests showed an increase in the hardness and diametrical compressive strength with the increase of volumetric fraction of (Mg) compared to the base alloy accompanied by a decrease in the rate of wear, The (XRD) test observes the composing phases (α(Cu4Al), β(Cu3Al), γ(Cu9Al44)) in addition to determining the transformation temperature from the Martensite to the Austenite by examining the (DSC) it was found that the Austenite initiation and finish (As), (Af) increased by adding the alloying elements (Mg)

Influence of the Yttria and Graphite Particles on the same of Al 2024 Alloy Properties

Powders have been mixed as (Al with 99% purity ≤53μm particle size, Cu with 99.5% purity ≤53μm particle size, Mg with 99.5% purity ≤53μm particle size, Y2O3 with 99.9% purity ≤53μm particle size, Gr with 99.9% purity ≤53μm particle size). one set of composite samples was prepared by addition (3wt%Gr) to metal powders shown above. For the each sample of composite varying (Y2O3) weight percentage as: (Al 2024-3wt%Gr-XY2O3) was added x=(0,2,4,6,8)(wt%) the other set of composite was in opposite. Well mixed samples was pressed uniaxial with (700Mpa) and (30sec). the compacted samples were sintered at (6000C) for (2hr). Results have shown an increase in bulk density by (5.3%) for (Al 2024-3wt% Gr-XY2O3) with the increase of reinforcement until (8wt%) of (Y2O3), while bulk density have been reduced for (Al 2024-3wt%Y2O3-XGr) with (5%) with the increase of (Gr) weight content in the composite. An increase in real porosity was noticed with the increase of (Y2O3) with (8wt%) (11.9%) for (Al 2024-3wt%Gr-XY2O3) but this was less in comparison with (Al 2024-3wt%Y2O3-XGr) were porosity increase with the increase of (Grwt%) up to reduced (18.5%) at (8wt%Gr).Mean value was of micro hardness decreased gradually with the increase of (Grwt%) to reach (19.4%) reduction at (8wt%Gr) in opposite the micro hardness mean value increased by (20%) as (Y2O3wt%) increased to (8wt%).Compression strength have was increased by (51%) as (Y2O3) content increased from (2-8)(wt%) for (Al 2024-3wt%Gr-XY2O3) composite, while it was decreased by (48%) with the addition of (8wt%) graphite to (Al 2024-3wt%Y2O3-XGr).The content of (Gr) had higher effect on wear rate than (Y2O3) where the wear rate decreased by (59.7%) and (41%) for composite samples respectively, within the limits of addition in the current study

The Influence of Graphite Content and Milling Time on Hardness, Compressive Strength and Wear Volume of Copper - Graphite Composites Prepared Via Powder Metallurgy

Copper – graphite composites are widely used in sliding bearings and brushes due to their excellent thermal and electrical conductivities and high wear resistance. The aim of this research is to study the Influence of graphite content and milling time on hardness, compressive strength, wear volume and friction coefficient of copper - graphite composites prepared via powder metallurgy. A powder mixture containing 0,5,10,15,20 and 25 vol% graphite was milled for 1,3,5,7 and 9 hours. The milled mixture was cold pressed at 700 MPa for 30 second, followed by sintering at 900 oC for one hour. It was found through this work that increasing milling time results an appreciate increase in hardness and radial compressive strength, slight reduction in wear volume and slight increase in the coefficient of friction for all compositions except that for pure copper in which a considerable increase in wear volume and decrease in the coefficient of friction was observed. On the other hand, increasing the graphite volume fraction increases the composite hardness, till an optimum value, and decreases the radial compressive strength. A great decrease in both wear volume and coefficient of friction was observed on increasing graphite content up to 25 vol%. Finally, a graphite, cast iron chips and fireclay sintering configuration was found to be an effective procedure which minimize oxidation to levels comparative with those observed previously by sintering in argon or hydrogen atmospheres. DOI: http://dx.doi.org/10.25130/tjes.24.2017.31</p

The Influence of Graphite Content and Milling Time on Hardness, Compressive Strength and Wear Volume of Copper - Graphite Composites Prepared Via Powder Metallurgy

Copper – graphite composites are widely used in sliding bearings and brushes due to their excellent thermal and electrical conductivities and high wear resistance. The aim of this research is to study the Influence of graphite content and milling time on hardness, compressive strength, wear volume and friction coefficient of copper - graphite composites prepared via powder metallurgy. A powder mixture containing 0,5,10,15,20 and 25 vol% graphite was milled for 1,3,5,7 and 9 hours. The milled mixture was cold pressed at 700 MPa for 30 second, followed by sintering at 900 oC for one hour. It was found through this work that increasing milling time results an appreciate increase in hardness and radial compressive strength, slight reduction in wear volume and slight increase in the coefficient of friction for all compositions except that for pure copper in which a considerable increase in wear volume and decrease in the coefficient of friction was observed. On the other hand, increasing the graphite volume fraction increases the composite hardness, till an optimum value, and decreases the radial compressive strength. A great decrease in both wear volume and coefficient of friction was observed on increasing graphite content up to 25 vol%. Finally, a graphite, cast iron chips and fireclay sintering configuration was found to be an effective procedure which minimize oxidation to levels comparative with those observed previously by sintering in argon or hydrogen atmospheres. DOI: http://dx.doi.org/10.25130/tjes.24.2017.31</p