Key Engineering Materials Vol. 837

Abstract: Computer simulation of the process of ingotless rolling-extruding (IRE) of aluminum alloy rods with a content of 0.15% zirconium in the Deform 3D software package performed. The temperature, speed and deformation parameters of the treatment of the investigated alloy determined under different process conditions. To check the adequacy of the models, rod samples were made on a CRE-200 laboratory unit at specified processing parameters. Using the Deform 3D software package, the forces acting on the rolls and the extruding die during the IRE determined and their comparison with tensometric experimental data presented. The mechanical properties, electrical resistivity of semi-finished products after processing by the method of ingotless rolling-extruding and for conditions of their heating to 230 °C investigated. Technological recommendations for the manufacture of deformed semi-finished products using the method of ingotless rolling-extruding are proposed.

Abstract: The article presents the investigation results of the structure and properties of rods of aluminum alloys containing zirconium, cerium and lanthanum after ingotless rolling-extruding (IRE) and heat treatment. The patterns of changes in the microstructure, mechanical properties, electrical resistivity depending on the chemical composition of the alloys, processed by the IRE method and various modes of rods annealing are shown. A metallographic analysis of the grain structure of the samples in a deformed state and after annealing performed. The temperatures at which the alloy structure remains stable and maintains the level of operational properties revealed. The effect of chemical composition on the heat resistance of deformed semi-finished products represented. The study made it possible to evaluate the level of properties of experimental alloys after processing by the method of ingotless rolling-extruding and various modes of rods annealing.

Abstract: The dynamic measurement model for the interface cavities of the diffusion welded joint, which based on the effective resistivity, is established by using the damage factor and the Derby Model of the Bridgman Law. Then the quantitative relationship, which between the direct current potential and the effective area of the joint at high temperature and high pressure, can be obtained. In addition, on the basis of the dynamic four-probe DC potential method and the fieldbus technology, the computer measuring system is established, so that the creep propagation behaviour for the interface cavities of the 316L stainless steel can be monitored in real-time.

Abstract: The creep and rupture test were carried out on a non-standard specimen of 316L stainless steel (316L-SS) diffused bonding joint. And the θ-projection model was used to analyze the minimum creep strain rate and the remaining life at 500°C/6 MPa when the creep strain is 0.2%. According to the test results, design criterion for the diffusion bonding component at high temperature is established. The rupture experimental results show that the remaining life extrapolated by Larsen-Miller equation is relatively consistent with that calculated by the θ project concept method.

Abstract: The present paper aims at utilizing the 3-wire electroslag welding (ESW) to join high-speed pearlitic rail steels where microstructure and mechanical properties were investigated. The welded joint has produced an improved fracture force of 1396KN. WM was consisted of ferrite and pearlite having hardness of 27HRC, tensile strength of 748MPa and toughness of 12J, successively. HAZ was composed of pro-eutectoid ferrite and pearlite, where austenite grain size and pearlite colony size were reduced by moving away from the fusion line. In HAZ, near to the fusion line, the austenite grain size was 143±19μm, pearlite colony size was 52±9μm and pearlite interlamellar spacing was 90±27nm, which has produced hardness of 43.5HRC, tensile strength of 1228MPa, and toughness of 8J, successively. The entire investigation concludes that 3-wire ESW is an optimum and viable method, which has provided fine pearlite microstructure along with improved hardness and tensile strength.

Abstract: Effect of Ta-alloying on microstructure, martensitic transformation, mechanical property and shape memory effect of Ni₅₄Mn₂₅Ga_17.5Ta_0.5 alloy has been systematically investigated. The results show that the substructure of Ni-Mn-Ga alloy significantly changed, which was converted from the plate martensite to the lath martensite. Compression tests show that a compressive strength of 1380 MPa with a fracture strain up to 21.92% can be achieved in the Ni₅₄Mn₂₅Ga_17.5Ta_0.5 alloy at room temperature. This is no changed martensite structure with non-modulated T martensite. In addition, the martensitic transition temperature obviously decreases from 350 °C to 208 °Cand hysteresis loop increases about 20 °Cwhen Ta substituted of Ni. The shape memory effect increased with the increase of pre-deformation, nevertheless, the shape recovery ratio appeared firstly increases and then decreases. When the pre-deformation is 10%, 15%, 20%, the shape memory effect of the alloy is 5.1%, 6.8% and 10%, respectively.

Abstract: In order to determine the evolution features of deformation twins for TA2 commercial pure titanium (cp-TA2), the TA2 samples were bent under different bending angles in three-point bending tests via a universal testing machine. The electron backscatter diffraction (EBSD) technique was applied to identify the grain boundaries (GBs) and twin boundaries (TBs) in the bending areas. The results reveal that the type of deformation area would effect the evolution of different deformation twins. It is inferred that the state of stress would promote the multiplication of the same type of deformation twins.

Abstract: The ceramic surface treatment of aluminum alloy is an important means to improve the mechanical properties and corrosion resistance of aluminum alloy.This paper focuses on the process and research status of aluminum alloy anodic oxidation technology and aluminum alloy micro-arc oxidation technology and analyzes the future development direction.

Abstract: Ti–6Al–4V alloy (Ti64) with different microstructures was first preshocked at ~6–13 GPa and then compression reloaded at 4×10³s^-1 to investigate the effect of microstructure and shock prestrain on the dynamic mechanical behavior of this alloy. The strengthening effect caused by shock prestrain is weaker than that introduced by the uniaxial stress compression during dynamic reloading process regardless of microstructure type and impact stress amplitude. However, the shock-induced enhancement ratio is higher in Ti64 having bimodal microstructures or the lamellar microstructure with wide α-platelets. These mechanical behaviors exhibited by postshock materials are closely related to the shock-induced microstructure evolution. Dislocations more tend to nucleate and interact in large-sized α phases such as equiaxed primary α and wide α-platelets. The generation of high-density micro-defects during the propagation of shock waves results in the improvement of strength but degradation of ductility of Ti64 during dynamic reloading process.