Because of the outstanding properties of aluminum, it is widely used in today's advanced technological world. However, its insufficient wear resistance limits its use for commercial and industrial applications. In this study, we performed DC diode plasma carburizing of aluminum in the gas composition of CH<sub>4</sub>&#x2013;H<sub>2</sub> (20&#x2013;80&#x25;) and at a temperature of about 350&#xb0;C for 4 and 8 hours. The corrosion properties of the untreated and plasma-carburized samples were evaluated using anodic polarization tests in 3&#x2009;N HCl solution according to ASTM: G5-94. The metallurgical characteristics were then investigated using XRD and SEM. The results showed that the carburizing process improves the corrosion resistance of treated specimens at low temperature.

Somayeh Pirizadhejrandoost

Mehdi Bakhshzad Mahmoudi

Elnaz Ahmadi

Masoud Moradshahi

The Corrosion Behavior of Carburized Aluminum Using DC Plasma

This paper investigates the effect of limestone, bauxite, fluorspar, and quartzite additions on the magnesium recovery in FeSiMg production from dolomite. Also, it illustrates the validation of the previous designed model. According to the model, magnesium content in the product alloy is calculated by the equation <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>[</mml:mo><mml:mtext>Mg</mml:mtext><mml:mo>]</mml:mo><mml:mo>=</mml:mo><mml:mo>(</mml:mo><mml:msub><mml:mrow><mml:mtext>MgO</mml:mtext></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub><mml:mo>)</mml:mo><mml:mo>[</mml:mo><mml:msub><mml:mrow><mml:mtext>Si</mml:mtext></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub><mml:mo>]</mml:mo><mml:mo>[</mml:mo><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mi>K</mml:mi><mml:mi>t</mml:mi><mml:mo>[</mml:mo><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mtext>MgO</mml:mtext></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mo>)</mml:mo><mml:mo>-</mml:mo><mml:mo>[</mml:mo><mml:mrow><mml:mtext>S</mml:mtext><mml:msub><mml:mrow><mml:mtext>i</mml:mtext></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mo>]</mml:mo></mml:mrow><mml:mo>]</mml:mo></mml:mrow></mml:msup><mml:mo>-</mml:mo><mml:mn>1</mml:mn><mml:mo>]</mml:mo><mml:mo>/</mml:mo><mml:mo>(</mml:mo><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mtext>MgO</mml:mtext></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mo>)</mml:mo></mml:mrow><mml:mrow><mml:mo>[</mml:mo><mml:mrow><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mi>K</mml:mi><mml:mi>t</mml:mi><mml:mo>[</mml:mo><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mtext>MgO</mml:mtext></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mo>)</mml:mo><mml:mo>-</mml:mo><mml:mo>[</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mtext>Si</mml:mtext></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mo>]</mml:mo></mml:mrow><mml:mo>]</mml:mo></mml:mrow></mml:msup></mml:mrow><mml:mo>]</mml:mo></mml:mrow><mml:mo>-</mml:mo><mml:mo>[</mml:mo><mml:msub><mml:mrow><mml:mtext>Si</mml:mtext></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub><mml:mo>]</mml:mo><mml:mo>)</mml:mo></mml:math>, where [Mg] is the concentration of magnesium metal in ferrosilicon magnesium alloy in mol/L, [Si<sub>0</sub>] and (MgO<sub>0</sub>) are the initial concentrations of silicon and magnesium oxide in charge in mol/L, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>t</mml:mi></mml:math> is the time in seconds, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>K</mml:mi></mml:math> is the reaction rate constant (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>3</mml:mn><mml:mo>.</mml:mo><mml:mn>26588</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mrow><mml:mn>10</mml:mn></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>7</mml:mn></mml:mrow></mml:msup></mml:math> LSec<sup>−1</sup> mol<sup>−1</sup>). The results of the production process are compared with the model results. The deviation between the actual and predicted magnesium content decreases as fluorspar, limestone, and quartzite increase up to 12.8wt.%, 8wt.%, and 8wt.%, respectively, with increase in the amount of the additives, the magnesium content in the produced alloy becomes far from the predicted values. It was found also that the addition of bauxite increases the gap between the actual and predicted values of magnesium content. It was found that the deviation of the actual magnesium content from the predicted depends mainly on the viscosity of the slag.

Saeed Ghali

Mamdouh Eissa

Hoda El-Faramawy

Validation of FeSiMg Alloy Production Model for the Experimental Process

The effect of annealing temperature on electrical characteristics of iridium (Ir) and iridium/gold (Ir/Au) Schottky contacts to n-type InGaN have been investigated by means of current-voltage (<i>I-V</i>) and capacitance-voltage (<i  >C-V</i>) techniques. It is observed that the barrier height of Ir/n-InGaN and Au/Ir/n-InGaN Schottky diodes increases after annealing at <svg style="vertical-align:-0.17555pt;width:38.450001px;" id="M1" height="11.0375" version="1.1" viewBox="0 0 38.450001 11.0375" width="38.450001"  xmlns="http://www.w3.org/2000/svg">
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			<text transform="matrix(1,0,0,-1,-71.95,63.39)">
				<tspan style="font-size: 12.50px; " x="0" y="0">3</tspan>
				<tspan style="font-size: 12.50px; " x="6.2515001" y="0">0</tspan>
				<tspan style="font-size: 12.50px; " x="12.503" y="0">0</tspan>
			</text>

			<text transform="matrix(1,0,0,-1,-53.2,68.56)">
				<tspan style="font-size: 8.75px; " x="0" y="0">∘</tspan>
			</text>

			<text transform="matrix(1,0,0,-1,-49.63,63.39)">
				<tspan style="font-size: 12.50px; " x="0" y="0">C</tspan>
			</text>

		</g>
	</g>
</svg> for 1&#x2009;min in <svg style="vertical-align:-3.13504pt;width:17.5px;" id="M2" height="14.375" version="1.1" viewBox="0 0 17.5 14.375" width="17.5"  xmlns="http://www.w3.org/2000/svg">
	<g transform="matrix(1.25,0,0,-1.25,0,14.375)">
		<g transform="translate(72,-60.5)">
			<text transform="matrix(1,0,0,-1,-71.95,63.67)">
				<tspan style="font-size: 12.50px; " x="0" y="0">N</tspan>
			</text>

			<text transform="matrix(1,0,0,-1,-62.92,60.55)">
				<tspan style="font-size: 8.75px; " x="0" y="0">2</tspan>
			</text>

		</g>
	</g>
</svg> ambient compared to the as-deposited. However, the barrier heights are found to be decreased somewhat after annealing at <svg style="vertical-align:-0.17555pt;width:38.450001px;" id="M3" height="11.225" version="1.1" viewBox="0 0 38.450001 11.225" width="38.450001"  xmlns="http://www.w3.org/2000/svg">
	<g transform="matrix(1.25,0,0,-1.25,0,11.225)">
		<g transform="translate(72,-63.02)">
			<text transform="matrix(1,0,0,-1,-71.95,63.24)">
				<tspan style="font-size: 12.50px; " x="0" y="0">5</tspan>
				<tspan style="font-size: 12.50px; " x="6.2515001" y="0">0</tspan>
				<tspan style="font-size: 12.50px; " x="12.503" y="0">0</tspan>
			</text>

			<text transform="matrix(1,0,0,-1,-53.2,68.56)">
				<tspan style="font-size: 8.75px; " x="0" y="0">∘</tspan>
			</text>

			<text transform="matrix(1,0,0,-1,-49.63,63.24)">
				<tspan style="font-size: 12.50px; " x="0" y="0">C</tspan>
			</text>

		</g>
	</g>
</svg> for the both Ir and Ir/Au Schottky contacts. From the above observations, it is clear that the optimum annealing temperature for both Ir and Ir/Au Schottky contacts is <svg style="vertical-align:-0.17555pt;width:38.450001px;" id="M4" height="11.0375" version="1.1" viewBox="0 0 38.450001 11.0375" width="38.450001"  xmlns="http://www.w3.org/2000/svg">
	<g transform="matrix(1.25,0,0,-1.25,0,11.0375)">
		<g transform="translate(72,-63.17)">
			<text transform="matrix(1,0,0,-1,-71.95,63.39)">
				<tspan style="font-size: 12.50px; " x="0" y="0">3</tspan>
				<tspan style="font-size: 12.50px; " x="6.2515001" y="0">0</tspan>
				<tspan style="font-size: 12.50px; " x="12.503" y="0">0</tspan>
			</text>

			<text transform="matrix(1,0,0,-1,-53.2,68.56)">
				<tspan style="font-size: 8.75px; " x="0" y="0">∘</tspan>
			</text>

			<text transform="matrix(1,0,0,-1,-49.63,63.39)">
				<tspan style="font-size: 12.50px; " x="0" y="0">C</tspan>
			</text>

		</g>
	</g>
</svg>. Moreover, the barrier height (<svg style="vertical-align:-3.2316pt;width:15.975px;" id="M5" height="14.5875" version="1.1" viewBox="0 0 15.975 14.5875" width="15.975"  xmlns="http://www.w3.org/2000/svg">
	<g transform="matrix(1.25,0,0,-1.25,0,14.5875)">
		<g transform="translate(72,-60.33)">
			<text transform="matrix(1,0,0,-1,-71.95,63.6)">
				<tspan style="font-size: 12.50px; " x="0" y="0">𝜙</tspan>
			</text>

			<text transform="matrix(1,0,0,-1,-63.89,60.47)">
				<tspan style="font-size: 8.75px; " x="0" y="0">𝑏</tspan>
			</text>

		</g>
	</g>
</svg>), ideality factor (<i  >n</i>) and series resistance (<svg style="vertical-align:-3.22282pt;width:20.1875px;" id="M6" height="14.35" version="1.1" viewBox="0 0 20.1875 14.35" width="20.1875"  xmlns="http://www.w3.org/2000/svg">
	<g transform="matrix(1.25,0,0,-1.25,0,14.35)">
		<g transform="translate(72,-60.52)">
			<text transform="matrix(1,0,0,-1,-71.95,63.79)">
				<tspan style="font-size: 12.50px; " x="0" y="0">𝑅</tspan>
			</text>

			<text transform="matrix(1,0,0,-1,-62.7,60.66)">
				<tspan style="font-size: 8.75px; " x="0" y="0">𝑆</tspan>
			</text>

		</g>
	</g>
</svg>) are determined using Cheung&#x2019;s and Norde methods. Besides, the energy distribution of interface state densities are determined from the forward bias <i  >I-V</i> characteristics by taking into account the bias dependence of the effective barrier height.  Based on the above results, it is clear that both Ir and Ir/Au Schottky contacts exhibit a kind of thermal stability during annealing. 

V. Rajagopal Reddy

B. Prasanna Lakshmi

R. Padma

Electrical Properties of Rapidly Annealed Ir and Ir/Au Schottky Contacts on n-Type InGaN

The effect of microstructure on the stress-strain behaviour of pipeline steels was studied. Slow strain rate (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>2</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mrow><mml:mn>10</mml:mn></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>6</mml:mn></mml:mrow></mml:msup></mml:math> s<sup>-1</sup>) tests were conducted on grade X65 and X100 steels in silicone oil and hydrogen carbonate/carbonate solution. The as-received grade X100 steel at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow><mml:mn>75</mml:mn></mml:mrow><mml:mrow><mml:mo>°</mml:mo></mml:mrow></mml:msup></mml:math>C showed serrated stress-strain curves. The magnitude of the serrations depended upon the strain rate and test temperature. Annealing at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow><mml:mn>600</mml:mn></mml:mrow><mml:mrow><mml:mo>°</mml:mo></mml:mrow></mml:msup></mml:math>C or above removes the serrations, but this increased the susceptibility to transgranular cracking in hydrogen carbonate/carbonate solution at potentials below −800 mV (sce). The removal and reformation of banding in pipeline steels were also studied. Ferrite/pearlite becomes aligned during the hot rolling stage of pipe manufacture and causes directionality in crack propagation and mechanical properties. Heat treatments were carried out which show that banding in grade X65 and X100 can be removed above <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow><mml:mn>900</mml:mn></mml:mrow><mml:mrow><mml:mo>°</mml:mo></mml:mrow></mml:msup></mml:math>C. This depends on homogenisation of carbon which also depends on temperature, time, and cooling rate.

A. Mustapha

E. A. Charles

D. Hardie

The Effect of Microstructure on Stress-Strain Behaviour and Susceptibility to Cracking of Pipeline Steels

Cold pressing (CP) of the amorphous-like Co powder suppressed most of the XRD peaks, in particular the peak along (100) plane. The DSC curve of unmilled CP Co powder has shown a distinct sharp exothermic peak at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>615</mml:mn><mml:mtext>C</mml:mtext><mml:mo>°</mml:mo></mml:mrow></mml:math>. Upon annealing at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>700</mml:mn><mml:mtext>C</mml:mtext><mml:mo>°</mml:mo></mml:mrow></mml:math>, only the FCC phase with lattice parameter of 3.51 Å was detected by XRD. Our results implied that the exotherm at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>615</mml:mn><mml:mtext>C</mml:mtext><mml:mo>°</mml:mo></mml:mrow></mml:math> corresponds to compaction-pressure-assisted HCP to FCC first-order phase transition. The XRD analysis of 30 h milled powder revealed for the first time the FCC phase with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>a</mml:mi><mml:mo>=</mml:mo><mml:mn>3.80</mml:mn></mml:math> Å. However, due to presence of (100) and (210) peaks, this phase is thought to be FCT with lattice parameters <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>a</mml:mi><mml:mo>=</mml:mo><mml:mi>b</mml:mi><mml:mo>=</mml:mo><mml:mn>3.80</mml:mn></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>c</mml:mi><mml:mo>=</mml:mo><mml:mn>3.07</mml:mn></mml:math> Å. Consequently, the high-energy milling carried out in the current work induced for the first time HCP to FCT transition in Co. Upon CP of milled powder, the lattice parameter <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>a</mml:mi></mml:math> shrunk from 3.80 to 3.75 Å. However, during annealing of the CP milled Co powder at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>750</mml:mn><mml:mtext>C</mml:mtext><mml:mo>°</mml:mo></mml:mrow></mml:math>, the FCT to FCC transition occurred, yielding the FCC phase with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>a</mml:mi><mml:mo>=</mml:mo><mml:mn>3.51</mml:mn></mml:math> Å.

A. S. Bolokang

M. J. Phasha

D. E. Motaung

S. Bhero

Effect of Mechanical Milling and Cold Pressing on Co Powder

Microstructure evolution of Ti-6Al-4V alloy during hot backward extrusion process was simulated with the combined approaches of finite element method (FEM) and microstructure prediction model. From experimental analysis, it can be found that the change of microstructure during hot forming process of titanium alloy has a close relation to <inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>α</mml:mi></mml:mrow></mml:math></inline-formula>/<inline-formula><mml:math id="M2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>β</mml:mi></mml:mrow></mml:math></inline-formula> phase transformation and grain growth behaviour. A microstructure prediction model was established by considering the change of volume fractions and grain size of both phases varying with process variables and then implemented into the user-defined subroutine of FEM analysis. In order to demonstrate the reliability of the model, the volume fraction and grain size of primary <inline-formula><mml:math id="M3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>α</mml:mi></mml:mrow></mml:math></inline-formula> phase during the hot backward extrusion process of Ti-6Al-4V alloy were simulated. The simulation results were compared with the experimental ones.

Jong-Taek Yeom

Jeoung Han Kim

Jae-Keun Hong

Nho-Kwang Park

Chong Soo Lee

Prediction of Microstructure Evolution in Hot Backward Extrusion of Ti-6Al-4V Alloy

Plastic instability is reported in hexagonal close-packed (HCP) LA41 magnesium alloy during tensile tests. Serration amplitude associated with plastic instability is measured to increase with increasing strain and decrease with increasing strain rate. The model of dynamic strain aging (DSA) is proposed to be the controlling mechanism. Moreover, it is reported that annealing could reduce the flow instability, which has potential practical applications.

C. Wang

Y. B. Xu

E. H. Han

Investigations on the Plastic Instability in an HCP Mg-Li Alloy

A Re-rich phase (up to 85.40% wt.Re) was occasionally found in a single crystal superalloy during thermal exposure. Interestingly, this phase is located in front of the dendrite periphery in the interdendritic region, while the Re is segregated in the dendrite core. Formation of this phase was suggested to relate to the unusual accumulation of the Re resulting from the uneven diffusion process of Re. Appearance of this phase may imply the preference of forming Re-Re atomic bond in the superalloys.

Kuiyu Cheng

ChangYong Jo

DooHyun Kim

Tao Jin

Zhuangqi Hu

Unexpected Precipitation of a Re-Rich Phase in Single Crystal Superalloy CMSX-4 during Thermal Exposure

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Journal of Metallurgy