Development of powder material explosive sintering technology

image_pdfimage_print

Explosive sintering can also be called explosive compaction, which is a kind of explosion processing technology that sintering powder into compact material under transient high temperature and high pressure by the effect of shake wave and using the energy generated by explosive detonation or high-speed impact. It can be divided into axial symmetry explosive compaction and plane explosive compaction; besides, pre-heat explosive consolidation can be used in sintering ceramics and other refractory materials. Pre-heat explosive consolidation can solve the brittle crack problem that exist in the compaction and sintering of superhard ceramic powder, which can enlarge the tenacity of ceramic by heating and improve the sintering activity of particle interface at the same time.

metal powder explosive sinteringThe earliest explosive sintering was also originated from 1960’s, which was mainly used in the dynamic compaction and sintering research of tungsten, molybdenum and other refractory alloys at the beginning. Since the late 1980’s, as the world’s high technology research center has paid enough attention to new material, a number of studies have begun to be carried out on fine ceramic materials, metal matrix composites, intermetallic compounds amorphous and microcrystalline metastable materials. During this period, research on explosive sintering was also heating up. Scientists carried out the research on various ceramic materials and anchored their hope on sintering ceramic materials that have near 100 percents of theoretical density by using the explosive high pressure sintering. With the deepening of research, as the “cold” explosive sintering which is conducted under normal temperature will inevitably cause crack or microcrack in the material, explosive compaction resintering and pre-heat explosive sintering as well as shock wave chemical reaction assisted sintering and other methods appeared. The research objects are widely, which include aluminum oxide, zirconium oxide, silicon carbide, silicon nitride and other structural ceramics, barium titanate, lead zirconate titanate as well as YBCO superconductor and other functional ceramics. Almost at the same time, with the researches on amorphous state, microcrystal and other metalstable state alloys that carried out by metal material scientists, a series of rapid quenching, mechanical alloying (non-crystallizing) and other methods that used in producing low-dimensional materials were developed, besides, three-dimensional macro-scale materials are urgently needed to be prepared. Therefore, explosive sintering is also used in the researches on various metastable state alloys, such as iron-cobalt-nickel-based amorphous soft magnetic alloy, rapid quenched aluminum-lithium alloy and so on. Meanwhile, people have carried out a lot of researches on the explosive sintering of metal and composite materials, such as nickel-titanium memory alloy, SiC whiskers reinforced aluminum alloy and so on. Besides, they also have developed perfect macro explosive sintering theory. At present, explosive sintering technology has been widely used in the research of new materials and also has developed perfect mesocosmic combining theory on mechanics. Regarding metal materials, people have carried out successful explosive compaction researches on numerous metal and metal matrix composite powders, such as tungsten, molybdenum, titanium alloy, Ni-based superalloy, high temperature intermetallic compounds, metallic glass, microcrystal alloy as well as SiC whiskers reinforced aluminum alloy, W-Cu composite material, Al2O3 particles reinforced copper matrix alloy, tungsten-titanium alloy and so on. Regarding ceramic brittle materials, people also carried out a lot of explosive sintering researches on oxide, carbide and nitride ceramic and even obtained a certain research results on diamond, boron nitride and other superhard materials.

The disadvantage of explosive sintering is as follows: the workpiece that is sintered by this method will have single shape, which is not suitable for mechanized production; however, being served as unique powder processing technology, explosive sintering has short sintering time, large actuating pressure and will have rapid cooling quenching on the particle interface after “sintering”. Due to these characteristics, it will have unique advantages in the material preparation science compared with ordinary sintering forming technology, such as super high pressure compaction, hot isostatic pressing and so on. By using explosive super high pressure, very compact material can be made, for example, the sintered density of tungsten powder, titanium powder and other alloy powders can reach 95.6 percents to 99.6 percents T.D. (Theoretical Density); the sintered density of Si3N4 powder, SiC powder and other non-thermofusible ceramics can reach 95 percents to 98.6 percents T.D.; due to the fast fuse and fast setting of explosive sintering, it can prevent material grain coarsening caused by long time and high temperature sintering, which can be regarded as one of the most effective methods in sintering microcrystal and amorphous alloy material.