Study On The Microstructure And Properties Of New Aluminium-nickel Bronze Mould Material

In the production of modern industry, parts made by using die to form have the advantages of good quality, low cost, high production efficiency, save for raw material, energy saving and so on. Therefore, they have been applied in every field of industry widely and become an important means and a technology developing direction of modern industrial. The performance requirements of die materials have also been improved. Because of its low thermal conductivity, low thermal fatigue resistance and bad precision machining feature, the traditional alloy steel mould materials can not satisfy the actual operation requirements of some die materials. At present, Europe and America and other developed countries and some domestic institutions have studied and developed some copper alloy mold materials, which are used in extrusion, calendaring, extrusion and casting of metal and non-metal forming, especially in the field of polymer plastic and stainless steel forming. Due to the limitation of technology and equipment, our country is still not fully implement localization of copper alloy mould materials.According to the excellent comprehensive properties of aluminum bronze alloy, such as high hardness, good wear resistance and antifriction, high tensile and compressive strength, rigid stability, not easy to deformation, high thermal conductivity, fast heat and so on, this paper has developed a new kind of aluminum-nickel bronze mould material based on the study of the influence of alloy elements on the microstructure and properties of copper alloy. Then its melting and casting experiment is carried out by using the nonvacuum high-frequency induction furnace. The influence of several main elements with different Al, Ni and Fe contents on the microstructure and properties of the new alloy has been studied in detail by Using metallographic microscope, SEM, Brinell hardness tester, laser flash apparatus, electronic universal testing machine and other means, which is aimed at obtaining a new aluminum nickel mould material with excellent comprehensive performance. What is more, The effect of different heat treatment processes and friction and wear test parameters on the microstructure and properties of the new alloy has also been discussed. The results show as follow:The new alloy with different Al, Ni and Fe contents can influence its performance by changing the morphology, quantity and distribution of α phase, β′ phase, γ2 phase and κ phase. On the one hand, with the increase of Al content, The tensile strength of the new alloy rises at first and goes down latter. Its Brinell hardness rise continuously and its elongation decreases, then its wear loss decreases firstly and increases subsequently. On the other hand, with the increase of Ni and Fe content, the tensile strength, Brinell hardness and elongation of the new alloy rise first and then fall respectively. However, its wear loss decreases firstly and increases subsequently. When the contents of Al, Ni and Fe are 11.5%, 3.0% and 3.0% respectively, the new alloy shows high strength and hardness, good plastic toughness and excellent wear resistance.The optimum composition design of new aluminum nickel bronze mould is Al 11.5%, Ni 3.0%, Fe 3.0%, Mn 1.5%, B 0.15%, Zn 0.3% and the rest for Cu. The organization of as-cast alloy is mainly composed of α phase, β′ phase, γ2 phase and κ phase, there is a serious dendritic segregation phenomenon in which. What is more, there are uneven distributed κ phase, more(α+γ2) eutectoid phases and coarse microstructures in as-cast alloy, which has the tensile strength of 737 MPa, the Brinell hardness of 287 HBW, the extension rate of 5.9%, the thermal conductivity of 76 W/m·k and the wear mass of 1.34 mg. However, the tensile strength, the Brinell hardness, the extension rate, the thermal conductivity and the wear mass of the new alloy treated by the best heat treatment hardening process(540 ℃ for 3.5 h and then air-cooled aging after 940 ℃ for 2.5 h and then water-cooled solution) are 896 MPa, 415 HBW, 10.7%, 94 W/m·k and 0.83 mg respectively. Compared with as-cast alloy, heat treated alloy has higher strength and hardness, good toughness and ductility, excellent thermal conductivity and wear resistance.During the friction and wear process of new alloy with different heat treatment technologies, its wear mass shows a trend of increase gradually as test temperature, dry sliding velocity and load increase, and the wear curve of heat treated alloy is below as-cast alloy. In contrast to as-cast alloy, the average friction coefficient curve of hear treated alloy fluctuates in a smaller range, which is relatively smooth and similar to a straight line. The average friction coefficient of heat treated alloy is lower than as-cast alloy. The wear mechanisms of as-cast alloy are mainly abrasive wear at low temperature and adhesive wear at high temperature, adhesion wear and mild oxidative wear at low speed and adhesive wear at high speed, abrasive wear and oxidative wear at low load and adhesive wear at high load. Nevertheless, the wear mechanisms of heat treated alloy are mainly abrasive wear at low temperature and oxidative wear and adhesive wear at high temperature, oxidative wear at low speed and adhesion wear at high speed, abrasive wear at low load and fatigue wear and abrasive wear at high load.