Materials Science Forum Vols. 706-709

Abstract: The current investigation discusses the effect of Mn and Si contents on the microstructure and abrasive wear characteristic in Fe-based hard-facing alloy. A series of Fe-based hard-facing alloys are successfully fabricated onto the S45C steel by gas tungsten arc welding (GTAW). Results reveal that microstructure contains great amounts of martensite phases and moderate amounts of austenite phases. Si element added into Fe-based hard-facing alloy can not obviously affect the properties of the claddings, such as martensite phase, hardness, and abrasive wear resistance. Nevertheless, Mn element added into Fe-based hard-facing alloy can efficiently affect the martensite phase, hardness, and abrasive wear resistance of the claddings. The martensite contents decreases with the increasing of Mn contents in the cladding layers. The hardness increases as the Mn contents decreases, because the martensite contents increases. The abrasive wear resistance is not only related to the hardness of the cladding layer but the martensite contents of the cladding layer. The abrasive wear resistance is an inverse proportion to Mn contents of the cladding layers. Especially, the cladding layers containing 1.4Si-0.3Mn has the highest hardness of HRC 60.1 and the lowest wear loss of 0.37g.

Abstract: High purity elements such as magnesium, aluminum, silicon, titanium, vanadium, iron, nickel, copper, zinc, zirconium, molybdenum, palladium, silver, indium, tin, hafnium, gold and lead were processed by high-pressure torsion and subsequently evaluated by microstructural examinations and Vickers microhardness measurement. The grain size at the steady state, where the grain size and hardness remain unchanged with straining, was determined using either transmission electron microscopy, electron back-scatter diffraction analysis and/or optical microscopy. It is found that the steady state grain sizes are at the submicrometer level in elements with metallic bonding and at the nanometer level in elements with covalent bonding. The correlations between the steady-state grain size and the physical properties of metals are examined and it is found that the atomic bond energy and the homologous temperature are important parameters influencing the steady-state grain size after processing by HPT. A linear correlation between the hardness and grain size at the steady state is achieved by plotting the hardness normalized by the shear modulus against the grain size normalized by the Burgers vector in the logarithmic scale.

Abstract: The Plane Strain Compression and Static Recrystallisation Textures of BCC Metals Have Been Simulated Using a Coupled 3D Crystal Plasticity Finite Element (CPFE)-Single Phase Field (PF) Model Using an Interstitial-Free (IF) Steel as an Example. the Recrystallisation Nucleation Is Modelled Based on the Orientation Dependent Recovery (ODR) Theory which Assumes that Deformation Texture Components with a Relatively High Number of Slip Systems Activated during the Plane Strain Compression Undergo a Faster Recovery Process during the Subsequent Annealing due to the Cross Slip of Dislocations and as a Result Will Nucleate Earlier than Others. the Growth of Strain-Free Grains Is Simulated Using the Mis-Orientation Angle Dependent Grain Boundary Energy and Interface Mobility. A Linear Interpolation Method Is Adopted to Map the Data between the CPFE Model of Deformation and the Single PF Model of Recrystallisation. Simulated Results Show a Qualitative Agreement with the Typical Rolling and Annealing Textures Measured Experimentally for BCC Metals. Apart from the Texture and Grain Structure Formed during Deformation and Annealing, the Softening Fraction Can Also Be Simulated Using the Developed Model.

Abstract: This Research Focused on Studying the Effect of Silicon on the Hot Tearing Susceptibility of Permanent Mould Cast AZ91E Magnesium Alloy. Varying Amounts of Silicon (0.5, 1.0 and 1.5 Wt.%) Were Added to AZ91E in the Form of an Al-53 Wt.% Si Master Alloy. the Microstructure, Grain Size and Solidification Behavior of each Alloy Were Characterized and Related to their Tensile Properties and Hot Tearing Susceptibility. the Results Showed that the Tensile Strength and the Elongation of AZ91 Alloy Decreased with the Addition of Silicon at Room Temperature, due to the Formation of Chinese Script Mg2si Particles. however, Silicon Significantly Reduced the Hot Tearing Susceptibility of AZ91E. this Was Attributed to the Reduction of the Grain Size and the Decreased Freezing Range of AZ91E, which Contributed to Improve the Interdendritic Feeding during the Last Stage of Solidification.

Abstract: Mg Alloys Are the Lightest Structural Alloys with Excellent Castability and Machinability as Well as Highest Specific Strength and Stiffness. According to their Hexagonal close Packed Crystal Lattice there Is an Urgent Requirement of Mechanical Property Evaluation Method for Industrial Application, Particularly to Wrought Mg Alloys. Cyclic Loading Is a Very Popular Mode for Most Structural Application Situations. Recent Development of Fatigue Examination of Extruded Profile Has Shown that Mg Alloys Show Not so Ideal Fatigue Property. so that the Further Detailed Study on Cyclic Loading for Plastic Deformed Mg Alloys Is Needed. Tension-Tension Fatigue Tests Were Conducted on Pre-Strained AZ31 Mg Alloys that Produced by Rolling and Extruding Procedures. the Results Show that the Compressive Plastic Deformation Leads to Reduction of Fatigue Life/limit Significantly. SEM Analysis on Fatigue Fracture Surfaces Indicates that the Fatigue Cracks Initiate in the Surface or Sub-Surface of Dramatically Deformed Zones. the Microstructure Analysis Reveals that the Pre-Strain Brings More Abundant Twinning Bands with the Increase in Pre-Strain. the Decrease in Fatigue Life Demonstrates Also some Critical Feature with the Pre-Strain Level.